path: root/en_US.ISO8859-1/books/handbook/disks/chapter.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!--
     The FreeBSD Documentation Project

     $FreeBSD$
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<chapter xmlns="http://docbook.org/ns/docbook"
  xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
  xml:id="disks">

  <title>Storage</title>

  <sect1 xml:id="disks-synopsis">
    <title>Synopsis</title>

    <para>This chapter covers the use of disks and storage media in
      &os;.  This includes <acronym>SCSI</acronym> and
      <acronym>IDE</acronym> disks, <acronym>CD</acronym> and
      <acronym>DVD</acronym> media, memory-backed disks, and
      <acronym>USB</acronym> storage devices.</para>

    <para>After reading this chapter, you will know:</para>

    <itemizedlist>
      <listitem>
	<para>How to add additional hard disks to a &os;
	  system.</para>
      </listitem>

      <listitem>
	<para>How to grow the size of a disk's partition on
	  &os;.</para>
      </listitem>

      <listitem>
	<para>How to configure &os; to use <acronym>USB</acronym>
	  storage devices.</para>
      </listitem>

      <listitem>
	<para>How to use <acronym>CD</acronym> and
	  <acronym>DVD</acronym> media on a &os; system.</para>
      </listitem>

      <listitem>
	<para>How to use the backup programs available under
	  &os;.</para>
      </listitem>

      <listitem>
	<para>How to set up memory disks.</para>
      </listitem>

      <listitem>
	<para>What file system snapshots are and how to use them
	  efficiently.</para>
      </listitem>

      <listitem>
	<para>How to use quotas to limit disk space usage.</para>
      </listitem>

      <listitem>
	<para>How to encrypt disks and swap to secure them against
	  attackers.</para>
      </listitem>

      <listitem>
	<para>How to configure a highly available storage
	  network.</para>
      </listitem>
    </itemizedlist>

    <para>Before reading this chapter, you should:</para>

    <itemizedlist>
      <listitem>
	<para>Know how to <link linkend="kernelconfig">configure and
	    install a new &os; kernel</link>.</para>
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 xml:id="disks-adding">
    <info>
      <title>Adding Disks</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>David</firstname>
	    <surname>O'Brien</surname>
	  </personname>
	  <contrib>Originally contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>disks</primary>
      <secondary>adding</secondary>
    </indexterm>

    <para>This section describes how to add a new
      <acronym>SATA</acronym> disk to a machine that currently only
      has a single drive.  First, turn off the computer and install
      the drive in the computer following the instructions of the
      computer, controller, and drive manufacturers.  Reboot the
      system and become
      <systemitem class="username">root</systemitem>.</para>

    <para>Inspect <filename>/var/run/dmesg.boot</filename> to ensure
      the new disk was found.  In this example, the newly added
      <acronym>SATA</acronym> drive will appear as
      <filename>ada1</filename>.</para>

    <indexterm><primary>partitions</primary></indexterm>
    <indexterm>
      <primary><command>gpart</command></primary>
    </indexterm>

    <para>For this example, a single large partition will be created
      on the new disk.  The <link
	xlink:href="http://en.wikipedia.org/wiki/GUID_Partition_Table">
	<acronym>GPT</acronym></link> partitioning scheme will be
      used in preference to the older and less versatile
      <acronym>MBR</acronym> scheme.</para>

    <note>
      <para>If the disk to be added is not blank, old partition
	information can be removed with
	<command>gpart delete</command>.  See &man.gpart.8; for
	details.</para>
    </note>

    <para>The partition scheme is created, and then a single partition
      is added:</para>

    <screen>&prompt.root; <userinput>gpart create -s GPT ada1</userinput>
&prompt.root; <userinput>gpart add -t freebsd-ufs ada1</userinput></screen>

    <para>Depending on use, several smaller partitions may be desired.
      See &man.gpart.8; for options to create partitions smaller than
      a whole disk.</para>

    <para>A file system is created on the new blank disk:</para>

    <screen>&prompt.root; <userinput>newfs -U /dev/ada1p1</userinput></screen>

    <para>An empty directory is created as a
      <emphasis>mountpoint</emphasis>, a location for mounting the new
      disk in the original disk's file system:</para>

    <screen>&prompt.root; <userinput>mkdir /newdisk</userinput></screen>

    <para>Finally, an entry is added to
      <filename>/etc/fstab</filename> so the new disk will be mounted
      automatically at startup:</para>

    <programlisting>/dev/ada1p1	/newdisk	ufs	rw	2	2</programlisting>

    <para>The new disk can be mounted manually, without restarting the
      system:</para>

    <screen>&prompt.root; <userinput>mount /newdisk</userinput></screen>
  </sect1>

  <sect1 xml:id="disks-growing">
    <info>
      <title>Resizing and Growing Disks</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Allan</firstname>
	    <surname>Jude</surname>
	  </personname>
	  <contrib>Originally contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>disks</primary>
      <secondary>resizing</secondary>
    </indexterm>

    <para>A disk's capacity can increase without any changes to the
      data already present.  This happens commonly with virtual
      machines, when the virtual disk turns out to be too small and is
      enlarged.  Sometimes a disk image is written to a
      <acronym>USB</acronym> memory stick, but does not use the full
      capacity.  Here we describe how to resize or
      <emphasis>grow</emphasis> disk contents to take advantage of
      increased capacity.</para>

    <para>Determine the device name of the disk to be resized by
      inspecting <filename>/var/run/dmesg.boot</filename>.  In this
      example, there is only one <acronym>SATA</acronym> disk in the
      system, so the drive will appear as
      <filename>ada0</filename>.</para>

    <indexterm><primary>partitions</primary></indexterm>
    <indexterm>
      <primary><command>gpart</command></primary>
    </indexterm>

    <para>List the partitions on the disk to see the current
      configuration:</para>

    <screen>&prompt.root; <userinput>gpart show <replaceable>ada0</replaceable></userinput>
=>      34  83886013  ada0  GPT  (48G) [CORRUPT]
        34       128     1  freebsd-boot  (64k)
       162  79691648     2  freebsd-ufs  (38G)
  79691810   4194236     3  freebsd-swap  (2G)
  83886046         1        - free -  (512B)</screen>

    <note>
      <para>If the disk was formatted with the <link
	  xlink:href="http://en.wikipedia.org/wiki/GUID_Partition_Table">
	<acronym>GPT</acronym></link> partitioning scheme, it may show
	as <quote>corrupted</quote> because the <acronym>GPT</acronym>
	backup partition table is no longer at the end of the
	drive.  Fix the backup
	partition table with
	<command>gpart</command>:</para>

      <screen>&prompt.root; <userinput>gpart recover <replaceable>ada0</replaceable></userinput>
ada0 recovered</screen>
    </note>

    <para>Now the additional space on the disk is available for
      use by a new partition, or an existing partition can be
      expanded:</para>

    <screen>&prompt.root; <userinput>gpart show <replaceable>ada0</replaceable></userinput>
=>       34  102399933  ada0  GPT  (48G)
         34        128     1  freebsd-boot  (64k)
        162   79691648     2  freebsd-ufs  (38G)
   79691810    4194236     3  freebsd-swap  (2G)
   83886046   18513921        - free -  (8.8G)</screen>

    <para>Partitions can only be resized into contiguous free space.
      Here, the last partition on the disk is the swap partition, but
      the second partition is the one that needs to be resized.  Swap
      partitions only contain temporary data, so it can safely be
      unmounted, deleted, and then recreated after resizing other
      partitions.</para>

    <screen>&prompt.root; <userinput>swapoff <replaceable>/dev/ada0p3</replaceable></userinput>
&prompt.root; <userinput>gpart delete -i <replaceable>3</replaceable> <replaceable>ada0</replaceable></userinput>
ada0p3 deleted
&prompt.root; <userinput>gpart show <replaceable>ada0</replaceable></userinput>
=>       34  102399933  ada0  GPT  (48G)
         34        128     1  freebsd-boot  (64k)
        162   79691648     2  freebsd-ufs  (38G)
   79691810   22708157        - free -  (10G)</screen>

    <warning>
      <para>There is risk of data loss when modifying the partition
	table of a mounted file system.  It is best to perform the
	following steps on an unmounted file system while running from
	a live <acronym>CD-ROM</acronym> or <acronym>USB</acronym>
	device.  However, if absolutely necessary, a mounted file
	system can be  resized after disabling GEOM safety
	features:</para>

      <screen>&prompt.root; <userinput>sysctl kern.geom.debugflags=16</userinput></screen>
    </warning>

    <para>Resize the partition, leaving room to recreate a swap
      partition of the desired size.  This only modifies the size of
      the partition.  The file system in the partition will be
      expanded in a separate step.</para>

    <screen>&prompt.root; <userinput>gpart resize -i <replaceable>2</replaceable> -a 4k -s <replaceable>47G</replaceable> <replaceable>ada0</replaceable></userinput>
ada0p2 resized
&prompt.root; <userinput>gpart show <replaceable>ada0</replaceable></userinput>
=>       34  102399933  ada0  GPT  (48G)
         34        128     1  freebsd-boot  (64k)
        162   98566144     2  freebsd-ufs  (47G)
   98566306    3833661        - free -  (1.8G)</screen>

    <para>Recreate the swap partition:</para>

    <screen>&prompt.root; <userinput>gpart add -t freebsd-swap -a 4k <replaceable>ada0</replaceable></userinput>
ada0p3 added
&prompt.root; <userinput>gpart show <replaceable>ada0</replaceable></userinput>
=>       34  102399933  ada0  GPT  (48G)
         34        128     1  freebsd-boot  (64k)
        162   98566144     2  freebsd-ufs  (47G)
   98566306    3833661     3  freebsd-swap  (1.8G)
&prompt.root; <userinput>swapon <replaceable>/dev/ada0p3</replaceable></userinput></screen>

    <para>Grow the <acronym>UFS</acronym> file system to use the new
      capacity of the resized partition:</para>

    <note>
      <para>Growing a live <acronym>UFS</acronym> file system is only
	possible in &os; 10.0-RELEASE and later.  For earlier
	versions, the file system must not be mounted.</para>
    </note>

    <screen>&prompt.root; <userinput>growfs <replaceable>/dev/ada0p2</replaceable></userinput>
Device is mounted read-write; resizing will result in temporary write suspension for /.
It's strongly recommended to make a backup before growing the file system.
OK to grow file system on /dev/ada0p2, mounted on /, from 38GB to 47GB? [Yes/No] <userinput>Yes</userinput>
super-block backups (for fsck -b #) at:
 80781312, 82063552, 83345792, 84628032, 85910272, 87192512, 88474752,
 89756992, 91039232, 92321472, 93603712, 94885952, 96168192, 97450432</screen>

    <para>Both the partition and the file system on it have now been
      resized to use the newly-available disk space.</para>
  </sect1>

  <sect1 xml:id="usb-disks">
    <info>
      <title><acronym>USB</acronym> Storage Devices</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Marc</firstname>
	    <surname>Fonvieille</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>USB</primary>
      <secondary>disks</secondary>
    </indexterm>

    <para>Many external storage solutions, such as hard drives,
      <acronym>USB</acronym> thumbdrives, and <acronym>CD</acronym>
      and <acronym>DVD</acronym> burners, use the Universal Serial Bus
      (<acronym>USB</acronym>).  &os; provides support for
      <acronym>USB</acronym> 1.x, 2.0, and 3.0 devices.</para>

    <note>
      <para><acronym>USB</acronym> 3.0 support is not compatible with
	some hardware, including Haswell (Lynx point) chipsets.  If
	&os; boots with a <errorname>failed with error 19</errorname>
	message, disable xHCI/USB3 in the system
	<acronym>BIOS</acronym>.</para>
    </note>

    <para>Support for <acronym>USB</acronym> storage devices is built
      into the <filename>GENERIC</filename> kernel.  For a custom
      kernel, be sure that the following lines are present in the
      kernel configuration file:</para>

    <programlisting>device scbus	# SCSI bus (required for ATA/SCSI)
device da	# Direct Access (disks)
device pass	# Passthrough device (direct ATA/SCSI access)
device uhci	# provides USB 1.x support
device ohci	# provides USB 1.x support
device ehci	# provides USB 2.0 support
device xhci	# provides USB 3.0 support
device usb	# USB Bus (required)
device umass	# Disks/Mass storage - Requires scbus and da
device cd	# needed for CD and DVD burners</programlisting>

    <para>&os; uses the &man.umass.4; driver which uses the
      <acronym>SCSI</acronym> subsystem to access
      <acronym>USB</acronym> storage devices.  Since any
      <acronym>USB</acronym> device will be seen as a
      <acronym>SCSI</acronym> device by the system, if the
      <acronym>USB</acronym> device is a <acronym>CD</acronym> or
      <acronym>DVD</acronym> burner, do <emphasis>not</emphasis>
      include <option>device atapicam</option> in a custom kernel
      configuration file.</para>

    <para>The rest of this section demonstrates how to verify that a
      <acronym>USB</acronym> storage device is recognized by &os; and
      how to configure the device so that it can be used.</para>

    <sect2>
      <title>Device Configuration</title>

      <para>To test the <acronym>USB</acronym> configuration, plug in
	the <acronym>USB</acronym> device.  Use
	<command>dmesg</command> to confirm that the drive appears in
	the system message buffer.  It should look something like
	this:</para>

      <screen>umass0: &lt;STECH Simple Drive, class 0/0, rev 2.00/1.04, addr 3&gt; on usbus0
umass0:  SCSI over Bulk-Only; quirks = 0x0100
umass0:4:0:-1: Attached to scbus4
da0 at umass-sim0 bus 0 scbus4 target 0 lun 0
da0: &lt;STECH Simple Drive 1.04&gt; Fixed Direct Access SCSI-4 device
da0: Serial Number WD-WXE508CAN263
da0: 40.000MB/s transfers
da0: 152627MB (312581808 512 byte sectors: 255H 63S/T 19457C)
da0: quirks=0x2&lt;NO_6_BYTE&gt;</screen>

      <para>The brand, device node (<filename>da0</filename>), speed,
	and size will differ according to the device.</para>

      <para>Since the <acronym>USB</acronym> device is seen as a
	<acronym>SCSI</acronym> one, <command>camcontrol</command> can
	be used to list the <acronym>USB</acronym> storage devices
	attached to the system:</para>

      <screen>&prompt.root; <userinput>camcontrol devlist</userinput>
&lt;STECH Simple Drive 1.04&gt;          at scbus4 target 0 lun 0 (pass3,da0)</screen>

      <para>Alternately, <command>usbconfig</command> can be used to
	list the device.  Refer to &man.usbconfig.8; for more
	information about this command.</para>

      <screen>&prompt.root; <userinput>usbconfig</userinput>
ugen0.3: &lt;Simple Drive STECH&gt; at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=ON (2mA)</screen>

      <para>If the device has not been formatted, refer to <xref
	  linkend="disks-adding"/> for instructions on how to format
	and create partitions on the <acronym>USB</acronym> drive.  If
	the drive comes with a file system, it can be mounted by
	<systemitem class="username">root</systemitem> using the
	instructions in <xref linkend="mount-unmount"/>.</para>

      <warning>
	<para>Allowing untrusted users to mount arbitrary media, by
	  enabling <varname>vfs.usermount</varname> as described
	  below, should not be considered safe from a security point
	  of view.  Most file systems were not built to safeguard
	  against malicious devices.</para>
      </warning>

      <para>To make the device mountable as a normal user, one
	solution is to make all users of the device a member of the
	<systemitem class="groupname">operator</systemitem> group
	using &man.pw.8;.  Next, ensure that <systemitem
	  class="groupname">operator</systemitem> is able to read and
	write the device by adding these lines to
	<filename>/etc/devfs.rules</filename>:</para>

      <programlisting>[localrules=5]
add path 'da*' mode 0660 group operator</programlisting>

      <note>
	<para>If internal <acronym>SCSI</acronym> disks are also
	  installed in the system, change the second line as
	  follows:</para>

	<programlisting>add path 'da[<replaceable>3</replaceable>-9]*' mode 0660 group operator</programlisting>

	<para>This will exclude the first three
	  <acronym>SCSI</acronym> disks (<filename>da0</filename> to
	  <filename>da2</filename>)from belonging to the <systemitem
	    class="groupname">operator</systemitem> group.  Replace
	  <replaceable>3</replaceable> with the number of internal
	  <acronym>SCSI</acronym> disks.  Refer to &man.devfs.rules.5;
	  for more information about this file.</para>
      </note>

      <para>Next, enable the ruleset in
	<filename>/etc/rc.conf</filename>:</para>

      <programlisting>devfs_system_ruleset="localrules"</programlisting>

      <para>Then, instruct the system to allow regular users to mount
	file systems by adding the following line to
	<filename>/etc/sysctl.conf</filename>:</para>

      <programlisting>vfs.usermount=1</programlisting>

      <para>Since this only takes effect after the next reboot, use
	<command>sysctl</command> to set this variable now:</para>

      <screen>&prompt.root; <userinput>sysctl vfs.usermount=1</userinput>
vfs.usermount: 0 -&gt; 1</screen>

      <para>The final step is to create a directory where the file
	system is to be mounted.  This directory needs to be owned by
	the user that is to mount the file system.  One way to do that
	is for <systemitem class="username">root</systemitem> to
	create a subdirectory owned by that user as <filename
	  class="directory">/mnt/<replaceable>username</replaceable></filename>.
	In the following example, replace
	<replaceable>username</replaceable> with the login name of the
	user and <replaceable>usergroup</replaceable> with the user's
	primary group:</para>

      <screen>&prompt.root; <userinput>mkdir /mnt/<replaceable>username</replaceable></userinput>
&prompt.root; <userinput>chown <replaceable>username</replaceable>:<replaceable>usergroup</replaceable> /mnt/<replaceable>username</replaceable></userinput></screen>

      <para>Suppose a <acronym>USB</acronym> thumbdrive is plugged in,
	and a device <filename>/dev/da0s1</filename> appears.  If the
	device is formatted with a <acronym>FAT</acronym> file system,
	the user can mount it using:</para>

      <screen>&prompt.user; <userinput>mount -t msdosfs -o -m=644,-M=755 /dev/da0s1 /mnt/<replaceable>username</replaceable></userinput></screen>

      <para>Before the device can be unplugged, it
	<emphasis>must</emphasis> be unmounted first:</para>

      <screen>&prompt.user; <userinput>umount /mnt/<replaceable>username</replaceable></userinput></screen>

      <para>After device removal, the system message buffer will show
	messages similar to the following:</para>

      <screen>umass0: at uhub3, port 2, addr 3 (disconnected)
da0 at umass-sim0 bus 0 scbus4 target 0 lun 0
da0: &lt;STECH Simple Drive 1.04&gt; s/n WD-WXE508CAN263          detached
(da0:umass-sim0:0:0:0): Periph destroyed</screen>
    </sect2>
  </sect1>

  <sect1 xml:id="creating-cds">
    <info>
      <title>Creating and Using <acronym>CD</acronym> Media</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Mike</firstname>
	    <surname>Meyer</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary><acronym>CD-ROM</acronym>s</primary>
      <secondary>creating</secondary>
    </indexterm>

    <para>Compact Disc (<acronym>CD</acronym>) media provide a number
      of features that differentiate them from conventional disks.
      They are designed so that they can be read continuously without
      delays to move the head between tracks.  While
      <acronym>CD</acronym> media do have tracks, these refer to a
      section of data to be read continuously, and not a physical
      property of the disk.  The <acronym>ISO</acronym> 9660 file
      system was designed to deal with these differences.</para>

    <indexterm><primary><acronym>ISO</acronym>
      9660</primary></indexterm>
    <indexterm>
      <primary>file systems</primary>
      <secondary>ISO 9660</secondary>
    </indexterm>

    <indexterm>
      <primary><acronym>CD</acronym> burner</primary>
      <secondary><acronym>ATAPI</acronym></secondary>
    </indexterm>

    <para>The &os; Ports Collection provides several utilities for
      burning and duplicating audio and data <acronym>CD</acronym>s.
      This chapter demonstrates the use of several command line
      utilities.  For <acronym>CD</acronym> burning software with a
      graphical utility, consider installing the
      <package>sysutils/xcdroast</package> or
      <package>sysutils/k3b</package> packages or ports.</para>

    <sect2 xml:id="atapicam">
      <info>
	<title>Supported Devices</title>

	<authorgroup>
	  <author>
	    <personname>
	      <firstname>Marc</firstname>
	      <surname>Fonvieille</surname>
	    </personname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </info>

      <indexterm>
	<primary><acronym>CD</acronym> burner</primary>
	<secondary>ATAPI/CAM driver</secondary>
      </indexterm>

      <para>The <filename>GENERIC</filename> kernel provides support
	for <acronym>SCSI</acronym>,  <acronym>USB</acronym>, and
	<acronym>ATAPI</acronym> <acronym>CD</acronym> readers and
	burners.  If a custom kernel is used, the options that need to
	be present in the kernel configuration file vary by the type
	of device.</para>

      <para>For a <acronym>SCSI</acronym> burner, make sure these
	options are present:</para>

      <programlisting>device scbus	# SCSI bus (required for ATA/SCSI)
device da	# Direct Access (disks)
device pass	# Passthrough device (direct ATA/SCSI access)
device cd	# needed for CD and DVD burners</programlisting>

      <para>For a <acronym>USB</acronym> burner, make sure these
	options are present:</para>

      <programlisting>device scbus	# SCSI bus (required for ATA/SCSI)
device da	# Direct Access (disks)
device pass	# Passthrough device (direct ATA/SCSI access)
device cd	# needed for CD and DVD burners
device uhci	# provides USB 1.x support
device ohci	# provides USB 1.x support
device ehci	# provides USB 2.0 support
device xhci	# provides USB 3.0 support
device usb	# USB Bus (required)
device umass	# Disks/Mass storage - Requires scbus and da</programlisting>

      <para>For an <acronym>ATAPI</acronym> burner, make sure these
	options are present:</para>

      <programlisting>device ata	# Legacy ATA/SATA controllers
device scbus	# SCSI bus (required for ATA/SCSI)
device pass	# Passthrough device (direct ATA/SCSI access)
device cd	# needed for CD and DVD burners</programlisting>

      <note>
	<para>On &os; versions prior to 10.x, this line is also
	  needed in the kernel configuration file if the burner is an
	  <acronym>ATAPI</acronym> device:</para>

	<programlisting>device atapicam</programlisting>

	<para>Alternately, this driver can be loaded at boot time by
	  adding the following line to
	  <filename>/boot/loader.conf</filename>:</para>

	<programlisting>atapicam_load="YES"</programlisting>

	<para>This will require a reboot of the system as this driver
	  can only be loaded at boot time.</para>
      </note>

      <para>To verify that &os; recognizes the device, run
	<command>dmesg</command> and look for an entry for the device.
	On systems prior to 10.x, the device name in the first line of
	the output will be <filename>acd0</filename> instead of
	<filename>cd0</filename>.</para>

      <screen>&prompt.user; <userinput>dmesg | grep cd</userinput>
cd0 at ahcich1 bus 0 scbus1 target 0 lun 0
cd0: &lt;HL-DT-ST DVDRAM GU70N LT20&gt; Removable CD-ROM SCSI-0 device
cd0: Serial Number M3OD3S34152
cd0: 150.000MB/s transfers (SATA 1.x, UDMA6, ATAPI 12bytes, PIO 8192bytes)
cd0: Attempt to query device size failed: NOT READY, Medium not present - tray closed</screen>
    </sect2>

    <sect2 xml:id="cdrecord">
      <title>Burning a <acronym>CD</acronym></title>

      <para>In &os;, <command>cdrecord</command> can be used to burn
	<acronym>CD</acronym>s.  This command is installed with the
	<package>sysutils/cdrtools</package> package or port.</para>

      <note>
	<para>&os; 8.x includes the built-in
	  <command>burncd</command> utility for burning
	  <acronym>CD</acronym>s using an <acronym>ATAPI</acronym>
	  <acronym>CD</acronym> burner.  Refer to the manual page for
	  <command>burncd</command> for usage examples.</para>
      </note>

      <para>While <command>cdrecord</command> has many options, basic
	usage is simple.  Specify the name of the
	<acronym>ISO</acronym> file to burn and, if the system has
	multiple burner devices, specify the name of the device to
	use:</para>

      <screen>&prompt.root; <userinput>cdrecord <replaceable>dev=device</replaceable> <replaceable>imagefile.iso</replaceable></userinput></screen>

      <para>To determine the device name of the burner, use
	<option>-scanbus</option> which might produce results like
	this:</para>

      <indexterm>
	<primary><acronym>CD-ROM</acronym>s</primary>
	<secondary>burning</secondary>
      </indexterm>
      <screen>&prompt.root; <userinput>cdrecord -scanbus</userinput>
ProDVD-ProBD-Clone 3.00 (amd64-unknown-freebsd10.0) Copyright (C) 1995-2010 J&ouml;rg Schilling
Using libscg version 'schily-0.9'
scsibus0:
        0,0,0     0) 'SEAGATE ' 'ST39236LW       ' '0004' Disk
        0,1,0     1) 'SEAGATE ' 'ST39173W        ' '5958' Disk
        0,2,0     2) *
        0,3,0     3) 'iomega  ' 'jaz 1GB         ' 'J.86' Removable Disk
        0,4,0     4) 'NEC     ' 'CD-ROM DRIVE:466' '1.26' Removable CD-ROM
        0,5,0     5) *
        0,6,0     6) *
        0,7,0     7) *
scsibus1:
        1,0,0   100) *
        1,1,0   101) *
        1,2,0   102) *
        1,3,0   103) *
        1,4,0   104) *
        1,5,0   105) 'YAMAHA  ' 'CRW4260         ' '1.0q' Removable CD-ROM
        1,6,0   106) 'ARTEC   ' 'AM12S           ' '1.06' Scanner
        1,7,0   107) *</screen>

      <para>Locate the entry for the <acronym>CD</acronym> burner and
	use the three numbers separated by commas as the value for
	<option>dev</option>.  In this case, the Yamaha burner device
	is <literal>1,5,0</literal>, so the appropriate input to
	specify that device is <option>dev=1,5,0</option>.  Refer to
	the manual page for <command>cdrecord</command> for other ways
	to specify this value and for information on writing audio
	tracks and controlling the write speed.</para>

      <para>Alternately, run the following command to get the device
	address of the burner:</para>

      <screen>&prompt.root; <userinput>camcontrol devlist</userinput>
&lt;MATSHITA CDRW/DVD UJDA740 1.00&gt;   at scbus1 target 0 lun 0 (cd0,pass0)</screen>

      <para>Use the numeric values for <literal>scbus</literal>,
	<literal>target</literal>, and <literal>lun</literal>.  For
	this example, <literal>1,0,0</literal> is the device name to
	use.</para>
    </sect2>

    <sect2 xml:id="mkisofs">
      <title>Writing Data to an <acronym>ISO</acronym> File
	System</title>

      <para>In order to produce a data <acronym>CD</acronym>, the data
	files that are going to make up the tracks on the
	<acronym>CD</acronym> must be prepared before they can be
	burned to the <acronym>CD</acronym>.  In &os;,
	<package>sysutils/cdrtools</package> installs
	<command>mkisofs</command>, which can be used to produce an
	<acronym>ISO</acronym> 9660 file system that is an image of a
	directory tree within a &unix; file system.  The simplest
	usage is to specify the name of the <acronym>ISO</acronym>
	file to create and the path to the files to place into the
	<acronym>ISO</acronym> 9660 file system:</para>

      <screen>&prompt.root; <userinput>mkisofs -o <replaceable>imagefile.iso</replaceable> <replaceable>/path/to/tree</replaceable></userinput></screen>

      <indexterm>
	<primary>file systems</primary>
	<secondary>ISO 9660</secondary>
      </indexterm>

      <para>This command maps the file names in the specified path to
	names that fit the limitations of the standard
	<acronym>ISO</acronym> 9660 file system, and will exclude
	files that do not meet the standard for <acronym>ISO</acronym>
	file systems.</para>

      <indexterm>
	<primary>file systems</primary>
	<secondary>Joliet</secondary>
      </indexterm>

      <para>A number of options are available to overcome the
	restrictions imposed by the standard.  In particular,
	<option>-R</option> enables the Rock Ridge extensions common
	to &unix; systems and <option>-J</option> enables Joliet
	extensions used by &microsoft; systems.</para>

      <para>For <acronym>CD</acronym>s that are going to be used only
	on &os; systems, <option>-U</option> can be used to disable
	all filename restrictions.  When used with
	<option>-R</option>, it produces a file system image that is
	identical to the specified &os; tree, even if it violates the
	<acronym>ISO</acronym> 9660 standard.</para>

      <indexterm>
	<primary><acronym>CD-ROM</acronym>s</primary>
	<secondary>creating bootable</secondary>
      </indexterm>

      <para>The last option of general use is <option>-b</option>.
	This is used to specify the location of a boot image for use
	in producing an <quote>El Torito</quote> bootable
	<acronym>CD</acronym>.  This option takes an argument which is
	the path to a boot image from the top of the tree being
	written to the <acronym>CD</acronym>.  By default,
	<command>mkisofs</command> creates an <acronym>ISO</acronym>
	image in <quote>floppy disk emulation</quote> mode, and thus
	expects the boot image to be exactly 1200, 1440 or
	2880&nbsp;KB in size.  Some boot loaders, like the one used by
	the &os; distribution media, do not use emulation mode.  In
	this case, <option>-no-emul-boot</option> should be used.  So,
	if <filename>/tmp/myboot</filename> holds a bootable &os;
	system with the boot image in
	<filename>/tmp/myboot/boot/cdboot</filename>, this command
	would produce
	<filename>/tmp/bootable.iso</filename>:</para>

      <screen>&prompt.root; <userinput>mkisofs -R -no-emul-boot -b boot/cdboot -o /tmp/bootable.iso /tmp/myboot</userinput></screen>

      <para>The resulting <acronym>ISO</acronym> image can be mounted
	as a memory disk with:</para>

      <screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /tmp/bootable.iso -u 0</userinput>
&prompt.root; <userinput>mount -t cd9660 /dev/md0 /mnt</userinput></screen>

      <para>One can then verify that <filename>/mnt</filename> and
	<filename>/tmp/myboot</filename> are identical.</para>

      <para>There are many other options available for
	<command>mkisofs</command> to fine-tune its behavior.  Refer
	to &man.mkisofs.8; for details.</para>

      <note>
	<para>It is possible to copy a data <acronym>CD</acronym> to
	  an image file that is functionally equivalent to the image
	  file created with <command>mkisofs</command>.  To do so, use
	  <filename>dd</filename> with the device name as the input
	  file and the name of the <acronym>ISO</acronym> to create as
	  the output file:</para>

	<screen>&prompt.root; <userinput>dd if=/dev/<replaceable>cd0</replaceable> of=<replaceable>file.iso</replaceable> bs=2048</userinput></screen>

	<para>The resulting image file can be burned to
	  <acronym>CD</acronym> as described in <xref
	    linkend="cdrecord"/>.</para>
      </note>
    </sect2>

    <sect2 xml:id="mounting-cd">
      <title>Using Data <acronym>CD</acronym>s</title>

      <para>Once an <acronym>ISO</acronym> has been burned to a
	<acronym>CD</acronym>, it can be mounted by specifying the
	file system type, the name of the device containing the
	<acronym>CD</acronym>, and an existing mount point:</para>

      <screen>&prompt.root; <userinput>mount -t cd9660 <replaceable>/dev/cd0</replaceable> <replaceable>/mnt</replaceable></userinput></screen>

      <para>Since <command>mount</command> assumes that a file system
	is of type <literal>ufs</literal>, a <errorname>Incorrect
	  super block</errorname> error will occur if <literal>-t
	  cd9660</literal> is not included when mounting a data
	<acronym>CD</acronym>.</para>

      <para>While any data <acronym>CD</acronym> can be mounted this
	way, disks with certain <acronym>ISO</acronym> 9660 extensions
	might behave oddly.  For example, Joliet disks store all
	filenames in two-byte Unicode characters.  If some non-English
	characters show up as question marks, specify the local
	charset with <option>-C</option>.  For more information, refer
	to &man.mount.cd9660.8;.</para>

      <note>
	<para>In order to do this character conversion with the help
	  of <option>-C</option>, the kernel requires the
	  <filename>cd9660_iconv.ko</filename> module to be loaded.
	  This can be done either by adding this line to
	  <filename>loader.conf</filename>:</para>

	<programlisting>cd9660_iconv_load="YES"</programlisting>

	<para>and then rebooting the machine, or by directly loading
	  the module with <command>kldload</command>.</para>
      </note>

      <para>Occasionally, <errorname>Device not configured</errorname>
	will be displayed when trying to mount a data
	<acronym>CD</acronym>.  This usually means that the
	<acronym>CD</acronym> drive thinks that there is no disk in
	the tray, or that the drive is not visible on the bus.  It
	can take a couple of seconds for a <acronym>CD</acronym>
	drive to realize that a media is present, so be
	patient.</para>

      <para>Sometimes, a <acronym>SCSI</acronym>
	<acronym>CD</acronym> drive may be missed because it did not
	have enough time to answer the bus reset.  To resolve this,
	a custom kernel can be created which increases the default
	<acronym>SCSI</acronym> delay.  Add the following option to
	the custom kernel configuration file and rebuild the kernel
	using the instructions in <xref
	  linkend="kernelconfig-building"/>:</para>

      <programlisting>options SCSI_DELAY=15000</programlisting>

      <para>This tells the <acronym>SCSI</acronym> bus to pause 15
	seconds during boot, to give the <acronym>CD</acronym>
	drive every possible chance to answer the bus reset.</para>

      <note>
	<para>It is possible to burn a file directly to
	  <acronym>CD</acronym>, without creating an
	  <acronym>ISO</acronym> 9660 file system.  This is known as
	  burning a raw data <acronym>CD</acronym> and some people do
	  this for backup purposes.</para>

	<para>This type of disk can not be mounted as a normal data
	  <acronym>CD</acronym>.  In order to retrieve the data burned
	  to such a <acronym>CD</acronym>, the data must be read from
	  the raw device node.  For example, this command will extract
	  a compressed tar file located on the second
	  <acronym>CD</acronym> device into the current working
	  directory:</para>

	<screen>&prompt.root; <userinput>tar xzvf /dev/<replaceable>cd1</replaceable></userinput></screen>

	<para>  In order to mount a data <acronym>CD</acronym>, the
	  data must be written using
	  <command>mkisofs</command>.</para>
      </note>
    </sect2>

    <sect2 xml:id="duplicating-audiocds">
      <title>Duplicating Audio <acronym>CD</acronym>s</title>

      <para>To duplicate an audio <acronym>CD</acronym>, extract the
	audio data from the <acronym>CD</acronym> to a series of
	files, then write these files to a blank
	<acronym>CD</acronym>.</para>

      <para><xref linkend="using-cdrecord"/> describes how to
	duplicate and burn an audio <acronym>CD</acronym>.  If the
	&os; version is less than 10.0 and the device is
	<acronym>ATAPI</acronym>, the <option>atapicam</option> module
	must be first loaded using the instructions in <xref
	  linkend="atapicam"/>.</para>

      <procedure xml:id="using-cdrecord">
	<title>Duplicating an Audio <acronym>CD</acronym></title>

	<step>
	  <para>The <package>sysutils/cdrtools</package> package or
	    port installs <command>cdda2wav</command>.  This command
	    can be used to extract all of the audio tracks, with each
	    track written to a separate <acronym>WAV</acronym> file in
	    the current working directory:</para>

	  <screen>&prompt.user; <userinput>cdda2wav -vall -B -Owav</userinput></screen>

	  <para>A device name does not need to be specified if there
	    is only one <acronym>CD</acronym> device on the system.
	    Refer to the <command>cdda2wav</command> manual page for
	    instructions on how to specify a device and to learn more
	    about the other options available for this command.</para>
	</step>

	<step>
	  <para>Use <command>cdrecord</command> to write the
	    <filename>.wav</filename> files:</para>

	  <screen>&prompt.user; <userinput>cdrecord -v dev=<replaceable>2,0</replaceable> -dao -useinfo  *.wav</userinput></screen>

	  <para>Make sure that <replaceable>2,0</replaceable> is set
	    appropriately, as described in <xref
	      linkend="cdrecord"/>.</para>
	</step>
      </procedure>
    </sect2>
  </sect1>

  <sect1 xml:id="creating-dvds">
    <info>
      <title>Creating and Using <acronym>DVD</acronym> Media</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Marc</firstname>
	    <surname>Fonvieille</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
      <authorgroup>
	<author>
	  <personname>
	    <firstname>Andy</firstname>
	    <surname>Polyakov</surname>
	  </personname>
	  <contrib>With inputs from </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary><acronym>DVD</acronym></primary>
      <secondary>burning</secondary>
    </indexterm>

    <para>Compared to the <acronym>CD</acronym>, the
      <acronym>DVD</acronym> is the next generation of optical media
      storage technology.  The <acronym>DVD</acronym> can hold more
      data than any <acronym>CD</acronym> and is the standard for
      video publishing.</para>

    <para>Five physical recordable formats can be defined for a
      recordable <acronym>DVD</acronym>:</para>

    <itemizedlist>
      <listitem>
	<para>DVD-R: This was the first <acronym>DVD</acronym>
	  recordable format available.  The DVD-R standard is defined
	  by the <link
	    xlink:href="http://www.dvdforum.com/forum.shtml"><acronym>DVD</acronym>
	    Forum</link>.  This format is write once.</para>
      </listitem>

      <listitem>
	<para><acronym>DVD-RW</acronym>: This is the rewritable
	  version of the DVD-R standard.  A
	  <acronym>DVD-RW</acronym> can be rewritten about 1000
	  times.</para>
      </listitem>

      <listitem>
	<para><acronym>DVD-RAM</acronym>: This is a rewritable format
	  which can be seen as a removable hard drive.  However, this
	  media is not compatible with most
	  <acronym>DVD-ROM</acronym> drives and DVD-Video players as
	  only a few <acronym>DVD</acronym> writers support the
	  <acronym>DVD-RAM</acronym> format.  Refer to <xref
	    linkend="creating-dvd-ram"/> for more information on
	  <acronym>DVD-RAM</acronym> use.</para>
      </listitem>

      <listitem>
	<para><acronym>DVD+RW</acronym>: This is a rewritable format
	  defined by the <link
	    xlink:href="http://www.dvdrw.com/"><acronym>DVD+RW</acronym>
	    Alliance</link>.  A <acronym>DVD+RW</acronym> can be
	  rewritten about 1000 times.</para>
      </listitem>

      <listitem>
	<para>DVD+R: This format is the write once variation of the
	  <acronym>DVD+RW</acronym> format.</para>
      </listitem>
    </itemizedlist>

    <para>A single layer recordable <acronym>DVD</acronym> can hold up
      to 4,700,000,000&nbsp;bytes which is actually 4.38&nbsp;GB or
      4485&nbsp;MB as 1 kilobyte is 1024 bytes.</para>

    <note>
      <para>A distinction must be made between the physical media and
	the application.  For example, a DVD-Video is a specific file
	layout that can be written on any recordable
	<acronym>DVD</acronym> physical media such as DVD-R, DVD+R, or
	<acronym>DVD-RW</acronym>.  Before choosing the type of media,
	ensure that both the burner and the DVD-Video player are
	compatible with the media under consideration.</para>
    </note>

    <sect2>
      <title>Configuration</title>

      <para>To perform <acronym>DVD</acronym> recording, use
	&man.growisofs.1;.  This command is part of the
	<package>sysutils/dvd+rw-tools</package> utilities which
	support all <acronym>DVD</acronym> media types.</para>

      <para>These tools use the <acronym>SCSI</acronym> subsystem to
	access the devices, therefore <link
	  linkend="atapicam">ATAPI/CAM support</link> must be loaded
	or statically compiled into the kernel.  This support is not
	needed if the burner uses the <acronym>USB</acronym>
	interface.  Refer to <xref linkend="usb-disks"/> for more
	details on <acronym>USB</acronym> device configuration.</para>

      <para>DMA access must also be enabled for
	<acronym>ATAPI</acronym> devices, by adding the following line
	to <filename>/boot/loader.conf</filename>:</para>

      <programlisting>hw.ata.atapi_dma="1"</programlisting>

      <para>Before attempting to use
	<application>dvd+rw-tools</application>, consult the <link
	  xlink:href="http://fy.chalmers.se/~appro/linux/DVD+RW/hcn.html">Hardware
	  Compatibility Notes</link>.</para>

      <note>
	<para>For a graphical user interface, consider using
	  <package>sysutils/k3b</package> which provides a user
	  friendly interface to &man.growisofs.1; and many other
	  burning tools.</para>
      </note>
    </sect2>

    <sect2>
      <title>Burning Data <acronym>DVD</acronym>s</title>

      <para>Since &man.growisofs.1; is a front-end to <link
	  linkend="mkisofs">mkisofs</link>, it will invoke
	&man.mkisofs.8; to create the file system layout and perform
	the write on the <acronym>DVD</acronym>.  This means that an
	image of the data does not need to be created before the
	burning process.</para>

      <para>To burn to a DVD+R or a DVD-R the data in
	<filename>/path/to/data</filename>, use the following
	command:</para>

      <screen>&prompt.root; <userinput>growisofs -dvd-compat -Z <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/data</replaceable></userinput></screen>

      <para>In this example, <option>-J -R</option> is passed to
	&man.mkisofs.8;  to create an ISO 9660 file system with Joliet
	and Rock Ridge extensions.  Refer to &man.mkisofs.8; for more
	details.</para>

      <para>For the initial session recording, <option>-Z</option> is
	used for both single and multiple sessions.  Replace
	<replaceable>/dev/cd0</replaceable>, with the name of the
	<acronym>DVD</acronym> device.  Using
	<option>-dvd-compat</option> indicates that the disk will be
	closed and that the recording will be unappendable.  This
	should also provide better media compatibility with
	<acronym>DVD-ROM</acronym> drives.</para>

      <para>To burn a pre-mastered image, such as
	<replaceable>imagefile.iso</replaceable>, use:</para>

      <screen>&prompt.root; <userinput>growisofs -dvd-compat -Z <replaceable>/dev/cd0</replaceable>=<replaceable>imagefile.iso</replaceable></userinput></screen>

      <para>The write speed should be detected and automatically set
	according to the media and the drive being used.  To force the
	write speed, use  <option>-speed=</option>.  Refer to
	&man.growisofs.1; for example usage.</para>

      <note>
	<para>In order to support working files larger than 4.38GB, an
	  UDF/ISO-9660 hybrid file system must be created by passing
	  <option>-udf -iso-level 3</option> to &man.mkisofs.8; and
	  all related programs, such as &man.growisofs.1;.  This is
	  required only when creating an ISO image file or when
	  writing files directly to a disk.  Since a disk created this
	  way must be mounted as an UDF file system with
	  &man.mount.udf.8;, it will be usable only on an UDF aware
	  operating system.  Otherwise it will look as if it contains
	  corrupted files.</para>

	<para>To create this type of ISO file:</para>

	<screen>&prompt.user; <userinput>mkisofs -R -J -udf -iso-level 3 -o <replaceable>imagefile.iso</replaceable> <replaceable>/path/to/data</replaceable></userinput></screen>

	<para>To burn files directly to a disk:</para>

	<screen>&prompt.root; <userinput>growisofs -dvd-compat -udf -iso-level 3 -Z <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/data</replaceable></userinput></screen>

	<para>When an ISO image already contains large files, no
	  additional options are required for &man.growisofs.1; to
	  burn that image on a disk.</para>

	<para>Be sure to use an up-to-date version of
	  <package>sysutils/cdrtools</package>, which contains
	  &man.mkisofs.8;, as an older version may not contain large
	  files support.  If the latest version does not work, install
	  <package>sysutils/cdrtools-devel</package> and read its
	  &man.mkisofs.8;.</para>
      </note>
    </sect2>

    <sect2>
      <title>Burning a <acronym>DVD</acronym>-Video</title>

      <indexterm>
	<primary><acronym>DVD</acronym></primary>
	<secondary>DVD-Video</secondary>
      </indexterm>

      <para>A DVD-Video is a specific file layout based on the ISO
	9660 and micro-UDF (M-UDF) specifications.  Since DVD-Video
	presents a specific data structure hierarchy, a particular
	program such as <package>multimedia/dvdauthor</package> is
	needed to author the <acronym>DVD</acronym>.</para>

      <para>If an image of the DVD-Video file system already exists,
	it can be burned in the same way as any other image.  If
	<command>dvdauthor</command> was used to make the
	<acronym>DVD</acronym> and the result is in
	<filename>/path/to/video</filename>, the following command
	should be used to burn the DVD-Video:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable> -dvd-video <replaceable>/path/to/video</replaceable></userinput></screen>

      <para><option>-dvd-video</option> is passed to &man.mkisofs.8;
	to instruct it to create a DVD-Video file system layout.
	This option implies the <option>-dvd-compat</option>
	&man.growisofs.1; option.</para>
    </sect2>

    <sect2>
      <title>Using a <acronym>DVD+RW</acronym></title>

      <indexterm>
	<primary><acronym>DVD</acronym></primary>
	<secondary><acronym>DVD+RW</acronym></secondary>
      </indexterm>

      <para>Unlike CD-RW, a virgin <acronym>DVD+RW</acronym> needs to
	be formatted before first use.  It is
	<emphasis>recommended</emphasis> to let &man.growisofs.1; take
	care of this automatically whenever appropriate.  However, it
	is possible to use <command>dvd+rw-format</command> to format
	the <acronym>DVD+RW</acronym>:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format <replaceable>/dev/cd0</replaceable></userinput></screen>

      <para>Only perform this operation once and keep in mind that
	only virgin <acronym>DVD+RW</acronym> medias need to be
	formatted.  Once formatted, the <acronym>DVD+RW</acronym> can
	be burned as usual.</para>

      <para>To burn a totally new file system and not just append some
	data onto a <acronym>DVD+RW</acronym>, the media does not need
	to be blanked first.  Instead, write over the previous
	recording like this:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/newdata</replaceable></userinput></screen>

      <para>The <acronym>DVD+RW</acronym> format supports appending
	data to a previous recording.  This operation consists of
	merging a new session to the existing one as it is not
	considered to be multi-session writing.  &man.growisofs.1;
	will <emphasis>grow</emphasis> the ISO 9660 file system
	present on the media.</para>

      <para>For example, to append data to a
	<acronym>DVD+RW</acronym>, use the following:</para>

      <screen>&prompt.root; <userinput>growisofs -M <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/nextdata</replaceable></userinput></screen>

      <para>The same &man.mkisofs.8; options used to burn the
	initial session should be used during next writes.</para>

      <note>
	<para>Use <option>-dvd-compat</option> for better media
	  compatibility with <acronym>DVD-ROM</acronym> drives.  When
	  using <acronym>DVD+RW</acronym>, this option will not
	  prevent the addition of data.</para>
      </note>

      <para>To blank the media, use:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable>=<replaceable>/dev/zero</replaceable></userinput></screen>
    </sect2>

    <sect2>
      <title>Using a <acronym>DVD-RW</acronym></title>

      <indexterm>
	<primary><acronym>DVD</acronym></primary>
	<secondary><acronym>DVD-RW</acronym></secondary>
      </indexterm>

      <para>A <acronym>DVD-RW</acronym> accepts two disc formats:
	incremental sequential and restricted overwrite.  By default,
	<acronym>DVD-RW</acronym> discs are in sequential
	format.</para>

      <para>A virgin <acronym>DVD-RW</acronym> can be directly written
	without being formatted.  However, a non-virgin
	<acronym>DVD-RW</acronym> in sequential format needs to be
	blanked before writing a new initial session.</para>

      <para>To blank a <acronym>DVD-RW</acronym> in sequential
	mode:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format -blank=full <replaceable>/dev/cd0</replaceable></userinput></screen>

      <note>
	<para>A full blanking using <option>-blank=full</option> will
	  take about one hour on a 1x media.  A fast blanking can be
	  performed using <option>-blank</option>, if the
	  <acronym>DVD-RW</acronym> will be recorded in Disk-At-Once
	  (DAO) mode.  To burn the <acronym>DVD-RW</acronym> in DAO
	  mode, use the command:</para>

	<screen>&prompt.root; <userinput>growisofs -use-the-force-luke=dao -Z <replaceable>/dev/cd0</replaceable>=<replaceable>imagefile.iso</replaceable></userinput></screen>

	<para>Since &man.growisofs.1; automatically attempts to detect
	  fast blanked media and engage DAO write,
	  <option>-use-the-force-luke=dao</option> should not be
	  required.</para>

	<para>One should instead use restricted overwrite mode with
	  any <acronym>DVD-RW</acronym> as this format is more
	  flexible than the default of incremental sequential.</para>
      </note>

      <para>To write data on a sequential <acronym>DVD-RW</acronym>,
	use the same instructions as for the other
	<acronym>DVD</acronym> formats:</para>

      <screen>&prompt.root; <userinput>growisofs -Z <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/data</replaceable></userinput></screen>

      <para>To append some data to a previous recording, use
	<option>-M</option> with &man.growisofs.1;.  However, if data
	is appended on a <acronym>DVD-RW</acronym> in incremental
	sequential mode, a new session will be created on the disc and
	the result will be a multi-session disc.</para>

      <para>A <acronym>DVD-RW</acronym> in restricted overwrite format
	does not need to be blanked before a new initial session.
	Instead, overwrite the disc with <option>-Z</option>.  It is
	also possible to grow an existing ISO 9660 file system written
	on the disc with <option>-M</option>.  The result will be a
	one-session <acronym>DVD</acronym>.</para>

      <para>To put a <acronym>DVD-RW</acronym> in restricted overwrite
	format, the following command must be used:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format <replaceable>/dev/cd0</replaceable></userinput></screen>

      <para>To change back to sequential format, use:</para>

      <screen>&prompt.root; <userinput>dvd+rw-format -blank=full <replaceable>/dev/cd0</replaceable></userinput></screen>
    </sect2>

    <sect2>
      <title>Multi-Session</title>

      <para>Few <acronym>DVD-ROM</acronym> drives support
	multi-session DVDs and most of the time only read the first
	session.  DVD+R, DVD-R and <acronym>DVD-RW</acronym> in
	sequential format can accept multiple sessions.  The notion
	of multiple sessions does not exist for the
	<acronym>DVD+RW</acronym> and the <acronym>DVD-RW</acronym>
	restricted overwrite formats.</para>

      <para>Using the following command after an initial non-closed
	session on a DVD+R, DVD-R, or <acronym>DVD-RW</acronym> in
	sequential format, will add a new session to the disc:</para>

      <screen>&prompt.root; <userinput>growisofs -M <replaceable>/dev/cd0</replaceable> -J -R <replaceable>/path/to/nextdata</replaceable></userinput></screen>

      <para>Using this command with a <acronym>DVD+RW</acronym> or a
	<acronym>DVD-RW</acronym> in restricted overwrite mode will
	append data while merging the new session to the existing one.
	The result will be a single-session disc.  Use this method to
	add data after an initial write on these types of
	media.</para>

      <note>
	<para>Since some space on the media is used between each
	  session to mark the end and start of sessions, one should
	  add sessions with a large amount of data to optimize media
	  space.  The number of sessions is limited to 154 for a
	  DVD+R, about 2000 for a DVD-R, and 127 for a DVD+R Double
	  Layer.</para>
      </note>
    </sect2>

    <sect2>
      <title>For More Information</title>

      <para>To obtain more information about a <acronym>DVD</acronym>,
	use <command>dvd+rw-mediainfo
	  <replaceable>/dev/cd0</replaceable></command> while the
	disc in the specified drive.</para>

      <para>More information about
	<application>dvd+rw-tools</application> can be found in
	&man.growisofs.1;, on the <link
	  xlink:href="http://fy.chalmers.se/~appro/linux/DVD+RW/">dvd+rw-tools
	  web site</link>, and in the <link
	  xlink:href="http://lists.debian.org/cdwrite/">cdwrite
	  mailing list</link> archives.</para>

      <note>
	<para>When creating a problem report related to the use of
	  <application>dvd+rw-tools</application>, always include the
	  output of <command>dvd+rw-mediainfo</command>.</para>
      </note>
    </sect2>

    <sect2 xml:id="creating-dvd-ram">
      <title>Using a <acronym>DVD-RAM</acronym></title>

      <indexterm>
	<primary><acronym>DVD</acronym></primary>
	<secondary><acronym>DVD-RAM</acronym></secondary>
      </indexterm>

      <para><acronym>DVD-RAM</acronym> writers can use either a
	<acronym>SCSI</acronym> or <acronym>ATAPI</acronym> interface.
	For <acronym>ATAPI</acronym> devices, DMA access has to be
	enabled by adding the following line to
	<filename>/boot/loader.conf</filename>:</para>

      <programlisting>hw.ata.atapi_dma="1"</programlisting>

      <para>A <acronym>DVD-RAM</acronym> can be seen as a removable
	hard drive.  Like any other hard drive, the
	<acronym>DVD-RAM</acronym> must be formatted before it can be
	used.  In this example, the whole disk space will be formatted
	with a standard UFS2 file system:</para>

      <screen>&prompt.root; <userinput>dd if=/dev/zero of=<replaceable>/dev/acd0</replaceable> bs=2k count=1</userinput>
&prompt.root; <userinput>bsdlabel -Bw <replaceable>acd0</replaceable></userinput>
&prompt.root; <userinput>newfs <replaceable>/dev/acd0</replaceable></userinput></screen>

      <para>The <acronym>DVD</acronym> device,
	<filename>acd0</filename>, must be changed according to the
	configuration.</para>

      <para>Once the <acronym>DVD-RAM</acronym> has been formatted, it
	can be mounted as a normal hard drive:</para>

      <screen>&prompt.root; <userinput>mount <replaceable>/dev/acd0</replaceable> <replaceable>/mnt</replaceable></userinput></screen>

      <para>Once mounted, the <acronym>DVD-RAM</acronym> will be both
	readable and writeable.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="floppies">
    <title>Creating and Using Floppy Disks</title>

<!--
      <authorgroup>
	<author>
	  <personname>
	    <firstname>Julio</firstname>
	    <surname>Merino</surname>
	  </personname>
	  <contrib>Original work by </contrib>
	</author>
      </authorgroup>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Martin</firstname>
	    <surname>Karlsson</surname>
	  </personname>
	  <contrib>Rewritten by </contrib>
	</author>
      </authorgroup>
      -->

    <para>This section explains how to format a 3.5 inch floppy disk
      in &os;.</para>

    <procedure>
      <title>Steps to Format a Floppy</title>

      <para>A floppy disk needs to be low-level formatted before it
	can be used.  This is usually done by the vendor, but
	formatting is a good way to check media integrity.  To
	low-level format the floppy disk on &os;, use
	&man.fdformat.1;.  When using this utility, make note of any
	error messages, as these can help determine if the disk is
	good or bad.</para>

      <step>
	<para>To format the floppy, insert a new 3.5 inch floppy disk
	  into the first floppy drive and issue:</para>

	  <screen>&prompt.root; <userinput>/usr/sbin/fdformat -f 1440 /dev/fd0</userinput></screen>
      </step>

      <step>
	<para>After low-level formatting the disk, create a disk label
	  as it is needed by the system to determine the size of the
	  disk and its geometry.  The supported geometry values are
	  listed in <filename>/etc/disktab</filename>.</para>

	<para>To write the disk label, use &man.bsdlabel.8;:</para>

	<screen>&prompt.root; <userinput>/sbin/bsdlabel -B -w /dev/fd0 fd1440</userinput></screen>
      </step>

      <step>
	<para>The floppy is now ready to be high-level formatted with
	  a file system.  The floppy's file system can be either UFS
	  or FAT, where FAT is generally a better choice for
	  floppies.</para>

	<para>To format the floppy with FAT, issue:</para>

	<screen>&prompt.root; <userinput>/sbin/newfs_msdos /dev/fd0</userinput></screen>
      </step>
    </procedure>

    <para>The disk is now ready for use.  To use the floppy, mount it
      with &man.mount.msdosfs.8;.  One can also install and use
      <package>emulators/mtools</package> from the Ports
      Collection.</para>
  </sect1>

  <sect1 xml:id="backup-basics">
    <title>Backup Basics</title>

<!--
    <authorgroup>
	<author>
	  <personname>
	    <firstname>Lowell</firstname>
	    <surname>Gilbert</surname>
	  </personname>
	  <contrib>Original work by </contrib>
	</author>
      </authorgroup>
      -->

    <para>Implementing a backup plan is essential in order to have the
      ability to recover from disk failure, accidental file deletion,
      random file corruption, or complete machine destruction,
      including destruction of on-site backups.</para>

    <para>The backup type and schedule will vary, depending upon the
      importance of the data, the granularity needed for file
      restores, and the amount of acceptable downtime.  Some possible
      backup techniques include:</para>

    <itemizedlist>
      <listitem>
	<para>Archives of the whole system, backed up onto permanent,
	  off-site media.  This provides protection against all of the
	  problems listed above, but is slow and inconvenient to
	  restore from, especially for non-privileged users.</para>
      </listitem>

      <listitem>
	<para>File system snapshots, which are useful for restoring
	  deleted files or previous versions of files.</para>
      </listitem>

      <listitem>
	<para>Copies of whole file systems or disks which are
	  sychronized with another system on the network using a
	  scheduled <package>net/rsync</package>.</para>
      </listitem>

      <listitem>
	<para>Hardware or software <acronym>RAID</acronym>, which
	  minimizes or avoids downtime when a disk fails.</para>
      </listitem>
    </itemizedlist>

    <para>Typically, a mix of backup techniques is used.  For
      example, one could create a schedule to automate a weekly, full
      system backup that is stored off-site and to supplement this
      backup with hourly ZFS snapshots.  In addition, one could make a
      manual backup of individual directories or files before making
      file edits or deletions.</para>

    <para>This section describes some of the utilities which can be
      used to create and manage backups on a &os; system.</para>

    <sect2>
      <title>File System Backups</title>

      <indexterm>
	<primary>backup software</primary>
	<secondary>dump / restore</secondary>
      </indexterm>
      <indexterm>
	<primary><command>dump</command></primary>
      </indexterm>
      <indexterm>
	<primary><command>restore</command></primary>
      </indexterm>

      <para>The traditional &unix; programs for backing up a file
	system are &man.dump.8;, which creates the backup, and
	&man.restore.8;, which restores the backup.  These utilities
	work at the disk block level, below the abstractions of the
	files, links, and directories that are created by file
	systems.  Unlike other backup software,
	<command>dump</command> backs up an entire file system and is
	unable to backup only part of a file system or a directory
	tree that spans multiple file systems.  Instead of writing
	files and directories, <command>dump</command> writes the raw
	data blocks that comprise files and directories.</para>

      <note>
	<para>If <command>dump</command> is used on the root
	  directory, it will not back up <filename>/home</filename>,
	  <filename>/usr</filename> or many other directories since
	  these are typically mount points for other file systems or
	  symbolic links into those file systems.</para>
      </note>

      <para>When used to restore data, <command>restore</command>
	stores temporary files in <filename>/tmp/</filename> by
	default.  When using a recovery disk with a small
	<filename>/tmp</filename>, set <envar>TMPDIR</envar> to a
	directory with more free space in order for the restore to
	succeed.</para>

      <para>When using <command>dump</command>, be aware that some
	quirks remain from its early days in Version 6 of
	AT&amp;T &unix;,circa 1975.  The default parameters assume a
	backup to a 9-track tape, rather than to another type of media
	or to the high-density tapes available today.  These defaults
	must be overridden on the command line.</para>

      <indexterm>
	<primary><filename>.rhosts</filename></primary>
      </indexterm>
      <para>It is possible to backup a file system across the network
	to a another system or to a tape drive attached to another
	computer.  While the &man.rdump.8; and &man.rrestore.8;
	utilities can be used for this purpose, they are not
	considered to be secure.</para>

      <para>Instead, one can use <command>dump</command> and
	<command>restore</command> in a more secure fashion over an
	<acronym>SSH</acronym> connection.  This example creates a
	full, compressed backup of the <filename>/usr</filename> file
	system and sends the backup file to the specified host over a
	<acronym>SSH</acronym> connection.</para>

      <example>
	<title>Using <command>dump</command> over
	  <application>ssh</application></title>

	<screen>&prompt.root; <userinput>/sbin/dump -0uan -f - /usr | gzip -2 | ssh -c blowfish \
          targetuser@targetmachine.example.com dd of=/mybigfiles/dump-usr-l0.gz</userinput></screen>
      </example>

      <para>This example sets <envar>RSH</envar> in order to write the
	backup to a tape drive on a remote system over a
	<acronym>SSH</acronym> connection:</para>

      <example>
	<title>Using <command>dump</command> over
	  <application>ssh</application> with <envar>RSH</envar>
	  Set</title>

	<screen>&prompt.root; <userinput>env RSH=/usr/bin/ssh /sbin/dump -0uan -f targetuser@targetmachine.example.com:/dev/sa0 /usr</userinput></screen>
      </example>
    </sect2>

    <sect2>
      <title>Directory Backups</title>

      <indexterm>
	<primary>backup software</primary>
	<secondary><command>tar</command></secondary>
      </indexterm>

      <para>Several built-in utilities are available for backing up
	and restoring specified files and directories as
	needed.</para>

      <para>A good choice for making a backup of all of the files in a
	directory is &man.tar.1;.  This utility dates back to Version
	6 of AT&amp;T &unix; and by default assumes a recursive backup
	to a local tape  device.  Switches can be used to instead
	specify the name of a backup file.</para>

      <indexterm><primary><command>tar</command></primary></indexterm>

      <para>This example creates a compressed backup of the current
	directory and saves it to
	<filename>/tmp/mybackup.tgz</filename>.  When creating a
	backup file, make sure that the backup is not saved to the
	same directory that is being backed up.</para>

      <example>
	<title>Backing Up the Current Directory With
	  <command>tar</command></title>

      <screen>&prompt.root; <userinput>tar czvf <replaceable>/tmp/mybackup.tgz</replaceable> . </userinput></screen>
      </example>

      <para>To restore the entire backup, <command>cd</command> into
	the directory to restore into and specify the name of the
	backup.  Note that this will overwrite any newer versions of
	files in the restore directory.  When in doubt, restore to a
	temporary directory or specify the name of the file within the
	backup to restore.</para>

      <example>
	<title>Restoring Up the Current Directory With
	  <command>tar</command></title>

      <screen>&prompt.root; <userinput>tar xzvf <replaceable>/tmp/mybackup.tgz</replaceable></userinput></screen>
      </example>

      <para>There are dozens of available switches which are described
	in &man.tar.1;.  This utility also supports the use of exclude
	patterns to specify which files should not be included when
	backing up the specified directory or restoring files from a
	backup.</para>

      <indexterm>
	<primary>backup software</primary>
	<secondary><command>cpio</command></secondary>
      </indexterm>

      <para>To create a backup using a specified list of files and
	directories, &man.cpio.1; is a good choice.  Unlike
	<command>tar</command>, <command>cpio</command> does not know
	how to walk the directory tree and it must be provided the
	list of files to backup.</para>

      <para>For example, a list of files can be created using
	<command>ls</command> or <command>find</command>.  This
	example creates a recursive listing of the current directory
	which is then piped to  <command>cpio</command> in order to
	create an output backup file named
	<filename>/tmp/mybackup.cpio</filename>.</para>

      <example>
	<title>Using<command>ls</command> and <command>cpio</command>
	  to Make a Recursive Backup of the Current Directory</title>

      <screen>&prompt.root; <userinput>ls -R | cpio -ovF <replaceable>/tmp/mybackup.cpio</replaceable></userinput></screen>
      </example>

      <indexterm>
	<primary>backup software</primary>
	<secondary><command>pax</command></secondary>
      </indexterm>
      <indexterm><primary><command>pax</command></primary></indexterm>
      <indexterm><primary>POSIX</primary></indexterm>
      <indexterm><primary>IEEE</primary></indexterm>

      <para>A backup utility which tries to bridge the features
	provided by <command>tar</command> and <command>cpio</command>
	is &man.pax.1;.  Over the years, the various versions of
	<command>tar</command> and <command>cpio</command> became
	slightly incompatible.  &posix; created <command>pax</command>
	which attempts to read and write many of the various
	<command>cpio</command> and <command>tar</command> formats,
	plus new formats of its own.</para>

      <para>The <command>pax</command> equivalent to the previous
	examples would be:</para>

      <example>
	<title>Backing Up the Current Directory With
	  <command>pax</command></title>

      <screen>&prompt.root; <userinput>pax -wf <replaceable>/tmp/mybackup.pax</replaceable> .</userinput></screen>
      </example>
    </sect2>

    <sect2 xml:id="backups-tapebackups">
      <title>Using Data Tapes for Backups</title>

      <indexterm><primary>tape media</primary></indexterm>

      <para>While tape technology has continued to evolve, modern
	backup systems tend to combine off-site backups with local
	removable media.  &os; supports any tape drive that uses
	<acronym>SCSI</acronym>, such as <acronym>LTO</acronym> or
	<acronym>DAT</acronym>.  There is limited support for
	<acronym>SATA</acronym> and <acronym>USB</acronym> tape
	drives.</para>

      <para>For <acronym>SCSI</acronym> tape devices, &os; uses the
	&man.sa.4; driver and the <filename>/dev/sa0</filename>,
	<filename>/dev/nsa0</filename>, and
	<filename>/dev/esa0</filename> devices.  The physical device
	name is <filename>/dev/sa0</filename>.  When
	<filename>/dev/nsa0</filename> is used, the backup application
	will not rewind the tape after writing a file, which allows
	writing more than one file to a tape.  Using
	<filename>/dev/esa0</filename> ejects the tape after the
	device is closed.</para>

      <para>In &os;, <command>mt</command> is used to control
	operations of the tape drive, such as seeking through files on
	a tape or writing tape control marks to the tape.  For
	example, the first three files on a tape can be preserved by
	skipping past them before writing a new file:</para>

      <screen>&prompt.root; <userinput>mt -f /dev/nsa0 fsf 3</userinput></screen>

      <para>This utility supports many operations.  Refer to
	&man.mt.1; for details.</para>

      <para>To write a single file to tape using
	<command>tar</command>, specify the name of the tape device
	and the file to backup:</para>

      <screen>&prompt.root; <userinput>tar cvf /dev/sa0 <replaceable>file</replaceable></userinput></screen>

      <para>To recover files from a <command>tar</command> archive
	on tape into the current directory:</para>

      <screen>&prompt.root; <userinput>tar xvf /dev/sa0</userinput></screen>

      <para>To backup a <acronym>UFS</acronym> file system, use
	<command>dump</command>.  This examples backs up
	<filename>/usr</filename> without rewinding the tape when
	finished:</para>

      <screen>&prompt.root; <userinput>dump -0aL -b64 -f /dev/nsa0 /usr</userinput></screen>

      <para>To interactively restore files from a
	<command>dump</command> file on tape into the current
	directory:</para>

      <screen>&prompt.root; <userinput>restore -i -f /dev/nsa0</userinput></screen>
    </sect2>

    <sect2 xml:id="backups-programs-amanda">
      <title>Third-Party Backup Utilities</title>

      <indexterm>
	<primary>backup software</primary>
      </indexterm>

      <para>The &os; Ports Collection provides many third-party
	utilities which can be used to schedule the creation of
	backups, simplify tape backup, and make backups easier and
	more convenient.  Many of these applications are client/server
	based and can be used to automate the backups of a single
	system or all of the computers in a network.</para>

      <para>Popular utilities include
	<application>Amanda</application>,
	<application>Bacula</application>,
	<application>rsync</application>, and
	<application>duplicity</application>.</para>
    </sect2>

    <sect2>
      <title>Emergency Recovery</title>

      <para>In addition to regular backups, it is recommended to
	perform the following steps as part of an emergency
	preparedness plan.</para>

      <indexterm>
	<primary><command>bsdlabel</command></primary></indexterm>

      <para>Create a print copy of the output of the following
	commands:</para>

      <itemizedlist>
	<listitem>
	  <para><command>gpart show</command></para>
	</listitem>

	<listitem>
	  <para><command>more /etc/fstab</command></para>
	</listitem>

	<listitem>
	  <para><command>dmesg</command></para>
	</listitem>
      </itemizedlist>

      <indexterm><primary>livefs
	  <acronym>CD</acronym></primary></indexterm>

      <para>Store this printout and a copy of the installation media
	in a secure location.  Should an emergency restore be
	needed, boot into the installation media and select
	<literal>Live CD</literal> to access a rescue shell.  This
	rescue mode can be used to view the current state of the
	system, and if needed, to  reformat disks and restore data
	from backups.</para>

      <note>
	<para>The installation media for
	  &os;/&arch.i386;&nbsp;&rel2.current;-RELEASE does not
	  include a rescue shell.  For this version, instead
	  download and burn a Livefs <acronym>CD</acronym> image from
	  <uri
	    xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/releases/&arch.i386;/ISO-IMAGES/&rel2.current;/&os;-&rel2.current;-RELEASE-&arch.i386;-livefs.iso">ftp://ftp.FreeBSD.org/pub/FreeBSD/releases/&arch.i386;/ISO-IMAGES/&rel2.current;/&os;-&rel2.current;-RELEASE-&arch.i386;-livefs.iso</uri>.</para>
      </note>

      <para>Next, test the rescue shell and the backups.  Make notes
	of the procedure.  Store these notes with the media, the
	printouts, and the backups.  These notes may prevent the
	inadvertent destruction of the backups while under the stress
	of performing an emergency recovery.</para>

      <para>For an added measure of security, store the latest backup
	at a remote location which is physically separated from the
	computers and disk drives by a significant distance.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="disks-virtual">
    <info>
      <title>Memory Disks</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Marc</firstname>
	    <surname>Fonvieille</surname>
	  </personname>
	  <contrib>Reorganized and enhanced by </contrib>
	</author>
      </authorgroup>
    </info>

    <para>In addition to physical disks, &os; also supports the
      creation and use of memory disks.  One possible use for a
      memory disk is to access the contents of an
      <acronym>ISO</acronym> file system without the overhead of first
      burning it to a <acronym>CD</acronym> or <acronym>DVD</acronym>,
      then mounting the <acronym>CD/DVD</acronym> media.</para>

    <para>In &os;, the  &man.md.4; driver is used to provide support
      for memory disks.  The <filename>GENERIC</filename> kernel
      includes this driver.  When using a custom kernel configuration
      file, ensure it includes this line:</para>

    <programlisting>device md</programlisting>

    <sect2 xml:id="disks-mdconfig">
      <title>Attaching and Detaching Existing Images</title>

      <indexterm>
	<primary>disks</primary>
	<secondary>memory</secondary>
      </indexterm>

      <para>To mount an existing file system image, use
	<command>mdconfig</command> to specify the name of the
	<acronym>ISO</acronym> file and a free unit number.  Then,
	refer to that unit number to mount it on an existing mount
	point.  Once mounted, the files in the <acronym>ISO</acronym>
	will appear in the mount point.  This example attaches
	<replaceable>diskimage.iso</replaceable> to the memory device
	<filename>/dev/md0</filename> then mounts that memory device
	on <filename>/mnt</filename>:</para>

      <screen>&prompt.root; <userinput>mdconfig -f <replaceable>diskimage.iso</replaceable> -u <replaceable>0</replaceable></userinput>
&prompt.root; <userinput>mount /dev/md<replaceable>0</replaceable> <replaceable>/mnt</replaceable></userinput></screen>

      <para>If a unit number is not specified with
	<option>-u</option>, <command>mdconfig</command> will
	automatically allocate an unused memory device and output
	the name of the allocated unit, such as
	<filename>md4</filename>.  Refer to &man.mdconfig.8; for more
	details about this command and its options.</para>

      <indexterm>
	<primary>disks</primary>
	<secondary>detaching a memory disk</secondary>
      </indexterm>

      <para>When a memory disk is no longer in use, its resources
	should be released back to the system.  First, unmount the
	file system, then use <command>mdconfig</command> to detach
	the disk from the system and release its resources.  To
	continue this example:</para>

      <screen>&prompt.root; <userinput>umount /mnt</userinput>
&prompt.root; <userinput>mdconfig -d -u <replaceable>0</replaceable></userinput></screen>

      <para>To determine if any memory disks are still attached to the
	system, type <command>mdconfig -l</command>.</para>
    </sect2>

    <sect2 xml:id="disks-md-freebsd5">
      <title>Creating a File- or Memory-Backed Memory Disk</title>

      <indexterm>
	<primary>disks</primary>
	<secondary>memory file system</secondary>
      </indexterm>
      <para>&os; also supports memory disks where the storage to use
	is allocated from either a hard disk or an area of memory.
	The first method is commonly referred to as a file-backed file
	system and the second method as a memory-backed file system.
	Both types can be created using
	<command>mdconfig</command>.</para>

      <para>To create a new memory-backed file system, specify a type
	of <literal>swap</literal> and the size of the memory disk to
	create.  Then, format the memory disk with a file system and
	mount as usual.  This example creates a 5M memory disk on unit
	<literal>1</literal>.  That memory disk is then formatted with
	the <acronym>UFS</acronym> file system before it is
	mounted:</para>

      <screen>&prompt.root; <userinput>mdconfig -a -t swap -s <replaceable>5</replaceable>m -u <replaceable>1</replaceable></userinput>
&prompt.root; <userinput>newfs -U md<replaceable>1</replaceable></userinput>
/dev/md1: 5.0MB (10240 sectors) block size 16384, fragment size 2048
        using 4 cylinder groups of 1.27MB, 81 blks, 192 inodes.
        with soft updates
super-block backups (for fsck -b #) at:
 160, 2752, 5344, 7936
&prompt.root; <userinput>mount /dev/md<replaceable>1</replaceable> <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem 1K-blocks Used Avail Capacity  Mounted on
/dev/md1        4718    4  4338     0%    /mnt</screen>

      <para>To create a new file-backed memory disk, first allocate an
	area of disk to use.  This example creates an empty 5K file
	named <filename>newimage</filename>:</para>

      <screen>&prompt.root; <userinput>dd if=/dev/zero of=<replaceable>newimage</replaceable> bs=1k count=<replaceable>5</replaceable>k</userinput>
5120+0 records in
5120+0 records out</screen>

      <para>Next, attach that file to a memory disk, label the memory
	disk and format it with the <acronym>UFS</acronym> file
	system, mount the memory disk, and verify the size of the
	file-backed disk:</para>

      <screen>&prompt.root; <userinput>mdconfig -f <replaceable>newimage</replaceable> -u <replaceable>0</replaceable></userinput>
&prompt.root; <userinput>bsdlabel -w md<replaceable>0</replaceable> auto</userinput>
&prompt.root; <userinput>newfs md<replaceable>0</replaceable>a</userinput>
/dev/md0a: 5.0MB (10224 sectors) block size 16384, fragment size 2048
        using 4 cylinder groups of 1.25MB, 80 blks, 192 inodes.
super-block backups (for fsck -b #) at:
 160, 2720, 5280, 7840
&prompt.root; <userinput>mount /dev/md<replaceable>0</replaceable>a <replaceable>/mnt</replaceable></userinput>
&prompt.root; <userinput>df <replaceable>/mnt</replaceable></userinput>
Filesystem 1K-blocks Used Avail Capacity  Mounted on
/dev/md0a       4710    4  4330     0%    /mnt</screen>

      <para>It takes several commands to create a file- or
	memory-backed file system using <command>mdconfig</command>.
	&os; also comes with <command>mdmfs</command> which
	automatically configures a memory disk, formats it with the
	<acronym>UFS</acronym> file system, and mounts it.  For
	example, after creating <replaceable>newimage</replaceable>
	with <command>dd</command>, this one command is equivalent to
	running the <command>bsdlabel</command>,
	<command>newfs</command>, and <command>mount</command>
	commands shown above:</para>

      <screen>&prompt.root; <userinput>mdmfs -F <replaceable>newimage</replaceable> -s <replaceable>5</replaceable>m md<replaceable>0</replaceable> <replaceable>/mnt</replaceable></userinput></screen>

      <para>To instead create a new memory-based memory disk with
	<command>mdmfs</command>, use this one command:</para>

      <screen>&prompt.root; <userinput>mdmfs -s <replaceable>5</replaceable>m md<replaceable>1</replaceable> <replaceable>/mnt</replaceable></userinput></screen>

      <para>If the unit number is not specified,
	<command>mdmfs</command> will automatically select an unused
	memory device.  For more details about
	<command>mdmfs</command>, refer to &man.mdmfs.8;.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="snapshots">
    <info>
      <title>File System Snapshots</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Tom</firstname>
	    <surname>Rhodes</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>file systems</primary>
      <secondary>snapshots</secondary>
    </indexterm>

    <para>&os; offers a feature in conjunction with
      <link linkend="soft-updates">Soft Updates</link>: file system
      snapshots.</para>

    <para>UFS snapshots allow a user to create images of specified
      file systems, and treat them as a file.  Snapshot files must be
      created in the file system that the action is performed on, and
      a user may create no more than 20 snapshots per file system.
      Active snapshots are recorded in the superblock so they are
      persistent across unmount and remount operations along with
      system reboots.  When a snapshot is no longer required, it can
      be removed using &man.rm.1;.  While snapshots may be removed in
      any order, all the used space may not be acquired because
      another snapshot will possibly claim some of the released
      blocks.</para>

    <para>The un-alterable <option>snapshot</option> file flag is set
      by &man.mksnap.ffs.8; after initial creation of a snapshot file.
      &man.unlink.1; makes an exception for snapshot files since it
      allows them to be removed.</para>

    <para>Snapshots are created using &man.mount.8;.  To place a
      snapshot of <filename>/var</filename> in the
      file <filename>/var/snapshot/snap</filename>, use the following
      command:</para>

    <screen>&prompt.root; <userinput>mount -u -o snapshot /var/snapshot/snap /var</userinput></screen>

    <para>Alternatively, use &man.mksnap.ffs.8; to create the
      snapshot:</para>

    <screen>&prompt.root; <userinput>mksnap_ffs /var /var/snapshot/snap</userinput></screen>

    <para>One can find snapshot files on a file system, such as
      <filename>/var</filename>, using
      &man.find.1;:</para>

    <screen>&prompt.root; <userinput>find /var -flags snapshot</userinput></screen>

    <para>Once a snapshot has been created, it has several
      uses:</para>

    <itemizedlist>
      <listitem>
	<para>Some administrators will use a snapshot file for backup
	  purposes, because the snapshot can be transferred to
	  <acronym>CD</acronym>s or tape.</para>
      </listitem>

      <listitem>
	<para>The file system integrity checker, &man.fsck.8;, may be
	  run on the snapshot.  Assuming that the file system was
	  clean when it was mounted, this should always provide a
	  clean and unchanging result.</para>
      </listitem>

      <listitem>
	<para>Running &man.dump.8; on the snapshot will produce a dump
	  file that is consistent with the file system and the
	  timestamp of the snapshot.  &man.dump.8; can also take a
	  snapshot, create a dump image, and then remove the snapshot
	  in one command by using <option>-L</option>.</para>
      </listitem>

      <listitem>
	<para>The snapshot can be mounted as a frozen image of the
	  file system.  To &man.mount.8; the snapshot
	  <filename>/var/snapshot/snap</filename> run:</para>

	<screen>&prompt.root; <userinput>mdconfig -a -t vnode -o readonly -f /var/snapshot/snap -u 4</userinput>
&prompt.root; <userinput>mount -r /dev/md4 /mnt</userinput></screen>
      </listitem>
    </itemizedlist>

    <para>The frozen <filename>/var</filename> is now available
      through <filename>/mnt</filename>.  Everything will initially be
      in the same state it was during the snapshot creation time.  The
      only exception is that any earlier snapshots will appear as zero
      length files.  To unmount the snapshot, use:</para>

    <screen>&prompt.root; <userinput>umount /mnt</userinput>
&prompt.root; <userinput>mdconfig -d -u 4</userinput></screen>

    <para>For more information about <option>softupdates</option> and
      file system snapshots, including technical papers, visit
      Marshall Kirk McKusick's website at <uri
	xlink:href="http://www.mckusick.com/">http://www.mckusick.com/</uri>.</para>
  </sect1>

  <sect1 xml:id="quotas">
    <title>Disk Quotas</title>

    <indexterm>
      <primary>accounting</primary>
      <secondary>disk space</secondary>
    </indexterm>
    <indexterm><primary>disk quotas</primary></indexterm>

    <para>Disk quotas can be used to limit the amount of disk space or
      the number of files a user or members of a group may allocate on
      a per-file system basis.  This prevents one user or group of
      users from consuming all of the available disk space.</para>

    <para>This section describes how to configure disk quotas for the
      <acronym>UFS</acronym> file system.  To configure quotas on the
      <acronym>ZFS</acronym> file system, refer to <xref
	linkend="zfs-quotas"/></para>

    <sect2>
      <title>Enabling Disk Quotas</title>

      <para>To determine if the &os; kernel provides support for disk
	quotas:</para>

      <screen>&prompt.user; <userinput>sysctl kern.features.ufs_quota</userinput>
kern.features.ufs_quota: 1</screen>

      <para>In this example, the <literal>1</literal> indicates quota
	support.  If the value is instead <literal>0</literal>, add
	the following line to a custom kernel configuration file and
	rebuild the kernel using the instructions in <xref
	  linkend="kernelconfig"/>:</para>

      <programlisting>options QUOTA</programlisting>

      <para>Next, enable disk quotas in
	<filename>/etc/rc.conf</filename>:</para>

      <programlisting>quota_enable="YES"</programlisting>

      <indexterm>
	<primary>disk quotas</primary>
	<secondary>checking</secondary>
      </indexterm>
      <para>Normally on bootup, the quota integrity of each file
	system is checked by &man.quotacheck.8;.  This program insures
	that the data in the quota database properly reflects the data
	on the file system.  This is a time consuming process that
	will significantly affect the time the system takes to boot.
	To skip this step, add this variable to
	<filename>/etc/rc.conf</filename>:</para>

      <programlisting>check_quotas="NO"</programlisting>

      <para>Finally, edit <filename>/etc/fstab</filename> to enable
	disk quotas on a per-file system basis.  To enable per-user
	quotas on a file system, add <option>userquota</option> to the
	options field in the <filename>/etc/fstab</filename> entry for
	the file system to enable quotas on.  For example:</para>

      <programlisting>/dev/da1s2g   /home    ufs rw,userquota 1 2</programlisting>

      <para>To enable group quotas, use <option>groupquota</option>
	instead.  To enable both user and group quotas, separate the
	options with a comma:</para>

      <programlisting>/dev/da1s2g    /home    ufs rw,userquota,groupquota 1 2</programlisting>

      <para>By default, quota files are stored in the root directory
	of the file system as <filename>quota.user</filename> and
	<filename>quota.group</filename>.  Refer to &man.fstab.5; for
	more information.  Specifying an alternate location for the
	quota files is not recommended.</para>

      <para>Once the configuration is complete, reboot the system and
	<filename>/etc/rc</filename> will automatically run the
	appropriate commands to create the initial quota files for all
	of the quotas enabled in
	<filename>/etc/fstab</filename>.</para>

      <para>In the normal course of operations, there should be no
	need to manually run &man.quotacheck.8;, &man.quotaon.8;, or
	&man.quotaoff.8;.  However, one should read these manual pages
	to be familiar with their operation.</para>
    </sect2>

    <sect2>
      <title>Setting Quota Limits</title>

      <indexterm>
	<primary>disk quotas</primary>
	<secondary>limits</secondary>
      </indexterm>

      <para>To
	verify that quotas are enabled, run:</para>

      <screen>&prompt.root; <userinput>quota -v</userinput></screen>

      <para>There should be a one line summary of disk usage and
	current quota limits for each file system that quotas are
	enabled on.</para>

      <para>The system is now ready to be assigned quota limits with
	<command>edquota</command>.</para>

      <para>Several options are available to enforce limits on the
	amount of disk space a user or group may allocate, and how
	many files they may create.  Allocations can be limited based
	on disk space (block quotas), number of files (inode quotas),
	or a combination of both.  Each limit is further broken down
	into two categories: hard and soft limits.</para>

      <indexterm><primary>hard limit</primary></indexterm>
      <para>A hard limit may not be exceeded.  Once a user reaches a
	hard limit, no further allocations can be made on that file
	system by that user.  For example, if the user has a hard
	limit of 500 kbytes on a file system and is currently using
	490 kbytes, the user can only allocate an additional 10
	kbytes.  Attempting to allocate an additional 11 kbytes will
	fail.</para>

      <indexterm><primary>soft limit</primary></indexterm>
      <para>Soft limits can be exceeded for a limited amount of time,
	known as the grace period, which is one week by default.  If a
	user stays over their limit longer than the grace period, the
	soft limit turns into a hard limit and no further allocations
	are allowed.  When the user drops back below the soft limit,
	the grace period is reset.</para>

      <para>In the following example, the quota for the <systemitem
	  class="username">test</systemitem> account is being edited.
	When <command>edquota</command> is invoked, the editor
	specified by <envar>EDITOR</envar> is opened in order to edit
	the quota limits.  The default editor is set to
	<application>vi</application>.</para>

      <screen>&prompt.root; <userinput>edquota -u test</userinput>
Quotas for user test:
/usr: kbytes in use: 65, limits (soft = 50, hard = 75)
        inodes in use: 7, limits (soft = 50, hard = 60)
/usr/var: kbytes in use: 0, limits (soft = 50, hard = 75)
        inodes in use: 0, limits (soft = 50, hard = 60)</screen>

      <para>There are normally two lines for each file system that has
	quotas enabled.  One line represents the block limits and the
	other represents the inode limits.  Change the value to modify
	the quota limit.  For example, to raise the block limit on
	<filename>/usr</filename> to a soft limit of
	<literal>500</literal> and a hard limit of
	<literal>600</literal>, change the values in that line as
	follows:</para>

      <programlisting>/usr: kbytes in use: 65, limits (soft = 500, hard = 600)</programlisting>

      <para>The new quota limits take affect upon exiting the
	editor.</para>

      <para>Sometimes it is desirable to set quota limits on a range
	of users.  This can be done by first assigning the desired
	quota limit to a user.  Then, use <option>-p</option> to
	duplicate that quota to a specified range of user IDs
	(<acronym>UID</acronym>s).  The following command will
	duplicate those quota limits for <acronym>UID</acronym>s
	<literal>10,000</literal> through
	<literal>19,999</literal>:</para>

      <screen>&prompt.root; <userinput>edquota -p test 10000-19999</userinput></screen>

      <para>For more information, refer to &man.edquota.8;.</para>
    </sect2>

    <sect2>
      <title>Checking Quota Limits and Disk Usage</title>

      <indexterm>
	<primary>disk quotas</primary>
	<secondary>checking</secondary>
      </indexterm>

      <para>To check individual user or group quotas and disk usage,
	use &man.quota.1;.  A user may only examine their own quota
	and the quota of a group they are a member of.  Only the
	superuser may view all user and group quotas.  To get a
	summary of all quotas and disk usage for file systems with
	quotas enabled, use &man.repquota.8;.</para>

      <para>Normally, file systems that the user is not using any disk
	space on will not show in the output of
	<command>quota</command>, even if the user has a quota limit
	assigned for that file system.  Use <option>-v</option> to
	display those file systems.  The following is sample output
	from <command>quota -v</command> for a user that has quota
	limits on two file systems.</para>

      <programlisting>Disk quotas for user test (uid 1002):
     Filesystem  usage    quota   limit   grace   files   quota   limit   grace
           /usr      65*     50      75   5days       7      50      60
       /usr/var       0      50      75               0      50      60</programlisting>

      <indexterm><primary>grace period</primary></indexterm>

      <para>In this example, the user is currently 15 kbytes over the
	soft limit of 50 kbytes on <filename>/usr</filename> and has 5
	days of grace period left.  The asterisk <literal>*</literal>
	indicates that the user is currently over the quota
	limit.</para>
    </sect2>

    <sect2>
      <title>Quotas over NFS</title>

      <indexterm><primary>NFS</primary></indexterm>

      <para>Quotas are enforced by the quota subsystem on the
	<acronym>NFS</acronym> server.  The &man.rpc.rquotad.8; daemon
	makes quota information available to <command>quota</command>
	on <acronym>NFS</acronym> clients, allowing users on those
	machines to see their quota statistics.</para>

      <para>On the <acronym>NFS</acronym> server, enable
	<command>rpc.rquotad</command> by removing the
	<literal>#</literal> from this line in
	<filename>/etc/inetd.conf</filename>:</para>

      <programlisting>rquotad/1      dgram rpc/udp wait root /usr/libexec/rpc.rquotad rpc.rquotad</programlisting>

      <para>Then, restart <command>inetd</command>:</para>

      <screen>&prompt.root; <userinput>service inetd restart</userinput></screen>
    </sect2>
  </sect1>

  <sect1 xml:id="disks-encrypting">
    <info>
      <title>Encrypting Disk Partitions</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Lucky</firstname>
	    <surname>Green</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	  <affiliation>
	    <address>
	      <email>shamrock@cypherpunks.to</email>
	    </address>
	  </affiliation>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>disks</primary>
      <secondary>encrypting</secondary>
    </indexterm>

    <para>&os; offers excellent online protections against
      unauthorized data access.  File permissions and <link
	linkend="mac">Mandatory Access Control</link> (MAC) help
      prevent unauthorized users from accessing data while the
      operating system is active and the computer is powered up.
      However, the permissions enforced by the operating system are
      irrelevant if an attacker has physical access to a computer and
      can move the computer's hard drive to another system to copy and
      analyze the data.</para>

    <para>Regardless of how an attacker may have come into possession
      of a hard drive or powered-down computer, the
      <acronym>GEOM</acronym>-based cryptographic subsystems built
      into &os; are able to protect the data on the computer's file
      systems against even highly-motivated attackers with significant
      resources.  Unlike encryption methods that encrypt individual
      files, the built-in <command>gbde</command> and
      <command>geli</command> utilities can be used to transparently
      encrypt entire file systems.  No cleartext ever touches the hard
      drive's platter.</para>

    <para>This chapter demonstrates how to create an encrypted file
      system on &os;.  It first demonstrates the process using
      <command>gbde</command> and then demonstrates the same example
      using <command>geli</command>.</para>

    <sect2>
      <title>Disk Encryption with
	<application>gbde</application></title>

      <para>The objective of the &man.gbde.4; facility is to provide a
	formidable challenge for an attacker to gain access to the
	contents of a <emphasis>cold</emphasis> storage device.
	However, if the computer is compromised while up and running
	and the storage device is actively attached, or the attacker
	has access to a valid passphrase, it offers no protection to
	the contents of the storage device.  Thus, it is important to
	provide physical security while the system is running and to
	protect the passphrase used by the encryption
	mechanism.</para>

      <para>This facility provides several barriers to protect the
	data stored in each disk sector.  It encrypts the contents of
	a disk sector using 128-bit <acronym>AES</acronym> in
	<acronym>CBC</acronym> mode.  Each sector on the disk is
	encrypted with a different <acronym>AES</acronym> key.  For
	more information on the cryptographic design, including how
	the sector keys are derived from the user-supplied passphrase,
	refer to &man.gbde.4;.</para>

      <para>&os; provides a kernel module for
	<application>gbde</application> which can be loaded with this
	command:</para>

      <screen>&prompt.root; <userinput>kldload geom_bde</userinput></screen>

      <para>If using a custom kernel configuration file, ensure it
	contains this line:</para>

      <para><literal>options GEOM_BDE</literal></para>

      <para>The following example demonstrates adding a new hard drive
	to a system that will hold a single encrypted partition that
	will be mounted as <filename>/private</filename>.</para>

      <procedure>
	<title>Encrypting a Partition with
	  <application>gbde</application></title>

	<step>
	  <title>Add the New Hard Drive</title>

	  <para>Install the new drive to the system as explained in
	    <xref linkend="disks-adding"/>.  For the purposes of this
	    example, a new hard drive partition has been added as
	    <filename>/dev/ad4s1c</filename> and
	    <filename>/dev/ad0s1<replaceable>*</replaceable></filename>
	    represents the existing standard &os; partitions.</para>

	  <screen>&prompt.root; <userinput>ls /dev/ad*</userinput>
/dev/ad0        /dev/ad0s1b     /dev/ad0s1e     /dev/ad4s1
/dev/ad0s1      /dev/ad0s1c     /dev/ad0s1f     /dev/ad4s1c
/dev/ad0s1a     /dev/ad0s1d     /dev/ad4</screen>
	</step>

	<step>
	  <title>Create a Directory to Hold <command>gbde</command>
	    Lock Files</title>

	  <screen>&prompt.root; <userinput>mkdir /etc/gbde</userinput></screen>

	  <para>The <application>gbde</application> lock file
	    contains information that <application>gbde</application>
	    requires to access encrypted partitions.  Without access
	    to the lock file, <application>gbde</application> will not
	    be able to decrypt the data contained in the encrypted
	    partition without significant manual intervention which is
	    not supported by the software.  Each encrypted partition
	    uses a separate lock file.</para>
	</step>

	<step>
	  <title>Initialize the <command>gbde</command>
	    Partition</title>

	  <para>A <application>gbde</application> partition must be
	    initialized before it can be used.  This initialization
	    needs to be performed only once.  This command will open
	    the default editor, in order to set various configuration
	    options in a template.  For use with the
	    <acronym>UFS</acronym> file system, set the sector_size to
	    2048:</para>

	  <screen>&prompt.root; <userinput>gbde init /dev/ad4s1c -i -L /etc/gbde/ad4s1c.lock</userinput># &dollar;FreeBSD: src/sbin/gbde/template.txt,v 1.1.36.1 2009/08/03 08:13:06 kensmith Exp $
#
# Sector size is the smallest unit of data which can be read or written.
# Making it too small decreases performance and decreases available space.
# Making it too large may prevent filesystems from working.  512 is the
# minimum and always safe.  For UFS, use the fragment size
#
sector_size	=	2048
[...]</screen>

	  <para>Once the edit is saved, the user will be asked twice
	    to type the passphrase used to secure the data.  The
	    passphrase must be the same both times.  The ability of
	    <application>gbde</application> to protect data depends
	    entirely on the quality of the passphrase.  For tips on
	    how to select a secure passphrase that is easy to
	    remember, see <link
	      xlink:href="http://world.std.com/~reinhold/diceware.html">http://world.std.com/~reinhold/diceware.htm</link>.</para>

	  <para>This initialization creates a lock file for the
	    <application>gbde</application> partition.  In this
	    example, it is stored as
	    <filename>/etc/gbde/ad4s1c.lock</filename>.  Lock files
	    must end in <quote>.lock</quote> in order to be correctly
	    detected by the <filename>/etc/rc.d/gbde</filename> start
	    up script.</para>

	  <caution>
	    <para>Lock files <emphasis>must</emphasis> be backed up
	      together with the contents of any encrypted partitions.
	      Without the lock file, the legitimate owner will be
	      unable to access the data on the encrypted
	      partition.</para>
	  </caution>
	</step>

	<step>
	  <title>Attach the Encrypted Partition to the
	    Kernel</title>

	  <screen>&prompt.root; <userinput>gbde attach /dev/ad4s1c -l /etc/gbde/ad4s1c.lock</userinput></screen>

	  <para>This command will prompt to input the passphrase that
	    was selected during the initialization of the encrypted
	    partition.  The new encrypted device will appear in
	    <filename>/dev</filename> as
	    <filename>/dev/device_name.bde</filename>:</para>

	  <screen>&prompt.root; <userinput>ls /dev/ad*</userinput>
/dev/ad0        /dev/ad0s1b     /dev/ad0s1e     /dev/ad4s1
/dev/ad0s1      /dev/ad0s1c     /dev/ad0s1f     /dev/ad4s1c
/dev/ad0s1a     /dev/ad0s1d     /dev/ad4        /dev/ad4s1c.bde</screen>
	</step>

	<step>
	  <title>Create a File System on the Encrypted
	    Device</title>

	  <para>Once the encrypted device has been attached to the
	    kernel, a file system can be created on the device.  This
	    example creates a <acronym>UFS</acronym> file system with
	    soft updates enabled.  Be sure to specify the partition
	    which has a
	    <filename><replaceable>*</replaceable>.bde</filename>
	    extension:</para>

	  <screen>&prompt.root; <userinput>newfs -U /dev/ad4s1c.bde</userinput></screen>
	</step>

	<step>
	  <title>Mount the Encrypted Partition</title>

	  <para>Create a mount point and mount the encrypted file
	    system:</para>

	  <screen>&prompt.root; <userinput>mkdir /private</userinput>
&prompt.root; <userinput>mount /dev/ad4s1c.bde /private</userinput></screen>
	</step>

	<step>
	  <title>Verify That the Encrypted File System is
	    Available</title>

	  <para>The encrypted file system should now be visible and
	    available for use:</para>

	  <screen>&prompt.user; <userinput>df -H</userinput>
Filesystem        Size   Used  Avail Capacity  Mounted on
/dev/ad0s1a      1037M    72M   883M     8%    /
/devfs            1.0K   1.0K     0B   100%    /dev
/dev/ad0s1f       8.1G    55K   7.5G     0%    /home
/dev/ad0s1e      1037M   1.1M   953M     0%    /tmp
/dev/ad0s1d       6.1G   1.9G   3.7G    35%    /usr
/dev/ad4s1c.bde   150G   4.1K   138G     0%    /private</screen>
	</step>
      </procedure>

      <para>After each boot, any encrypted file systems must be
	manually re-attached to the kernel, checked for errors, and
	mounted, before the file systems can be used.  To configure
	these steps, add the following lines to
	<filename>/etc/rc.conf</filename>:</para>

      <programlisting>gbde_autoattach_all="YES"
gbde_devices="<replaceable>ad4s1c</replaceable>"
gbde_lockdir="/etc/gbde"</programlisting>

      <para>This requires that the passphrase be entered at the
	console at boot time.  After typing the correct passphrase,
	the encrypted partition will be mounted automatically.
	Additional <application>gbde</application> boot options are
	available and listed in &man.rc.conf.5;.</para>

<!--
What about bsdinstall?
-->
      <note>
	<para><application>sysinstall</application> is incompatible
	  with <application>gbde</application>-encrypted devices.  All
	  <filename>*.bde</filename> devices must be detached from the
	  kernel before starting <application>sysinstall</application>
	  or it will crash during its initial probing for devices.  To
	  detach the encrypted device used in the example, use the
	  following command:</para>

	<screen>&prompt.root; <userinput>gbde detach /dev/<replaceable>ad4s1c</replaceable></userinput></screen>
      </note>
    </sect2>

    <sect2 xml:id="disks-encrypting-geli">
      <info>
	<title>Disk Encryption with <command>geli</command></title>

	<authorgroup>
	  <author>
	    <personname>
	      <firstname>Daniel</firstname>
	      <surname>Gerzo</surname>
	    </personname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </info>

      <para>An alternative cryptographic <acronym>GEOM</acronym> class
	is available using <command>geli</command>.  This control
	utility adds some features and uses a different scheme for
	doing cryptographic work.  It provides the following
	features:</para>

      <itemizedlist>
	<listitem>
	  <para>Utilizes the &man.crypto.9; framework and
	    automatically uses cryptographic hardware when it is
	    available.</para>
	</listitem>

	<listitem>
	  <para>Supports multiple cryptographic algorithms such as
	    <acronym>AES</acronym>, Blowfish, and
	    <acronym>3DES</acronym>.</para>
	</listitem>

	<listitem>
	  <para>Allows the root partition to be encrypted.  The
	    passphrase used to access the encrypted root partition
	    will be requested during system boot.</para>
	</listitem>

	<listitem>
	  <para>Allows the use of two independent keys.</para>
	</listitem>

	<listitem>
	  <para>It is fast as it performs simple sector-to-sector
	    encryption.</para>
	</listitem>

	<listitem>
	  <para>Allows backup and restore of master keys.  If a user
	    destroys their keys, it is still possible to get access to
	    the data by restoring keys from the backup.</para>
	</listitem>

	<listitem>
	  <para>Allows a disk to attach with a random, one-time key
	    which is useful for swap partitions and temporary file
	    systems.</para>
	</listitem>
      </itemizedlist>

      <para>More features and usage examples can be found in
	&man.geli.8;.</para>

      <para>The following example describes how to generate a key file
	which will be used as part of the master key for the encrypted
	provider mounted under <filename>/private</filename>.  The key
	file will provide some random data used to encrypt the master
	key.  The master key will also be protected by a passphrase.
	The provider's sector size will be 4kB.  The example describes
	how to attach to the <command>geli</command> provider, create
	a file system on it, mount it, work with it, and finally, how
	to detach it.</para>

      <procedure>
	<title>Encrypting a Partition with
	  <command>geli</command></title>

	<step>
	  <title>Load <command>geli</command> Support</title>

	  <para>Support for <command>geli</command> is available as a loadable
	    kernel module.  To configure the system to automatically load the
	    module at boot time, add the following line to
	    <filename>/boot/loader.conf</filename>:</para>

	  <programlisting>geom_eli_load="YES"</programlisting>

	  <para>To load the kernel module now:</para>

	  <screen>&prompt.root; <userinput>kldload geom_eli</userinput></screen>

	  <para>For a custom kernel, ensure the kernel configuration
	    file contains these lines:</para>

	  <programlisting>options GEOM_ELI
device crypto</programlisting>
	</step>

	<step>
	  <title>Generate the Master Key</title>

	  <para>The following commands generate a master key
	    (<filename>/root/da2.key</filename>) that is protected
	    with a passphrase.  The data source for the key file is
	    <filename>/dev/random</filename> and the sector size of
	    the provider (<filename>/dev/da2.eli</filename>) is 4kB as
	    a bigger sector size provides better performance:</para>

	  <screen>&prompt.root; <userinput>dd if=/dev/random of=/root/da2.key bs=64 count=1</userinput>
&prompt.root; <userinput>geli init -s 4096 -K /root/da2.key /dev/da2</userinput>
Enter new passphrase:
Reenter new passphrase:</screen>

	  <para>It is not mandatory to use both a passphrase and a key
	    file as either method of securing the master key can be
	    used in isolation.</para>

	  <para>If the key file is given as <quote>-</quote>, standard
	    input will be used.  For example, this command generates
	    three key files:</para>

	  <screen>&prompt.root; <userinput>cat keyfile1 keyfile2 keyfile3 | geli init -K - /dev/da2</userinput></screen>
	</step>

	<step>
	  <title>Attach the Provider with the Generated Key</title>

	  <para>To attach the provider, specify the key file, the name
	    of the disk, and the passphrase:</para>

	  <screen>&prompt.root; <userinput>geli attach -k /root/da2.key /dev/da2</userinput>
Enter passphrase:</screen>

	  <para>This creates a new device with an
	    <filename>.eli</filename> extension:</para>

	  <screen>&prompt.root; <userinput>ls /dev/da2*</userinput>
/dev/da2  /dev/da2.eli</screen>
	</step>

	<step>
	  <title>Create the New File System</title>

	  <para>Next, format the device with the
	    <acronym>UFS</acronym> file system and mount it on an
	    existing mount point:</para>

	  <screen>&prompt.root; <userinput>dd if=/dev/random of=/dev/da2.eli bs=1m</userinput>
&prompt.root; <userinput>newfs /dev/da2.eli</userinput>
&prompt.root; <userinput>mount /dev/da2.eli <replaceable>/private</replaceable></userinput></screen>

	  <para>The encrypted file system should now be available for
	    use:</para>

	  <screen>&prompt.root; <userinput>df -H</userinput>
Filesystem     Size   Used  Avail Capacity  Mounted on
/dev/ad0s1a    248M    89M   139M    38%    /
/devfs         1.0K   1.0K     0B   100%    /dev
/dev/ad0s1f    7.7G   2.3G   4.9G    32%    /usr
/dev/ad0s1d    989M   1.5M   909M     0%    /tmp
/dev/ad0s1e    3.9G   1.3G   2.3G    35%    /var
/dev/da2.eli   150G   4.1K   138G     0%    /private</screen>
	</step>
      </procedure>

      <para>Once the work on the encrypted partition is done, and the
	<filename>/private</filename> partition is no longer needed,
	it is prudent to put the device into cold storage by
	unmounting and detaching the <command>geli</command> encrypted
	partition from the kernel:</para>

      <screen>&prompt.root; <userinput>umount /private</userinput>
&prompt.root; <userinput>geli detach da2.eli</userinput></screen>

      <para>A <filename>rc.d</filename> script is provided to
	simplify the mounting of <command>geli</command>-encrypted
	devices at boot time.  For this example, add these lines to
	<filename>/etc/rc.conf</filename>:</para>

      <programlisting>geli_devices="<replaceable>da2</replaceable>"
geli_da2_flags="-p -k /root/<replaceable>da2.key</replaceable>"</programlisting>

      <para>This configures <filename>/dev/da2</filename> as a
	<command>geli</command> provider with a master key of
	<filename>/root/da2.key</filename>.  The system will
	automatically detach the provider from the kernel before the
	system shuts down.  During the startup process, the script
	will prompt for the passphrase before attaching the provider.
	Other kernel messages might be shown before and after the
	password prompt.  If the boot process seems to stall, look
	carefully for the password prompt among the other messages.
	Once the correct passphrase is entered, the provider is
	attached.  The file system is then mounted, typically by an
	entry in <filename>/etc/fstab</filename>.  Refer to <xref
	  linkend="mount-unmount"/> for instructions on how to
	configure a file system to mount at boot time.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="swap-encrypting">
    <info>
      <title>Encrypting Swap</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Christian</firstname>
	    <surname>Br&uuml;ffer</surname>
	  </personname>
	  <contrib>Written by </contrib>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>swap</primary>
      <secondary>encrypting</secondary>
    </indexterm>

    <para>Like the encryption of disk partitions, encryption of swap
      space is used to protect sensitive information.  Consider an
      application that deals with passwords.  As long as these
      passwords stay in physical memory, they are not written to disk
      and will be cleared after a reboot.  However, if &os; starts
      swapping out memory pages to free space, the passwords may be
      written to the disk unencrypted.  Encrypting swap space can be a
      solution for this scenario.</para>

    <para>This section demonstrates how to configure an encrypted
      swap partition using &man.gbde.8; or &man.geli.8; encryption.
      It assumes a <acronym>UFS</acronym> file system where
      <filename>/dev/ad0s1b</filename> is the swap partition.</para>

    <sect2>
      <title>Configuring Encrypted Swap</title>

      <para>Swap partitions are not encrypted by default and should be
	cleared of any sensitive data before continuing.  To overwrite
	the current swap partition with random garbage, execute the
	following command:</para>

      <screen>&prompt.root; <userinput>dd if=/dev/random of=/dev/<replaceable>ad0s1b</replaceable> bs=1m</userinput></screen>

      <para>To encrypt the swap partition using &man.gbde.8;, add the
	<literal>.bde</literal> suffix to the swap line in
	<filename>/etc/fstab</filename>:</para>

      <programlisting># Device		Mountpoint	FStype	Options		Dump	Pass#
/dev/ad0s1b.bde		none		swap	sw		0	0</programlisting>

      <para>To instead encrypt the swap partition using &man.geli.8;,
	use the
	<literal>.eli</literal> suffix:</para>

      <programlisting># Device		Mountpoint	FStype	Options		Dump	Pass#
/dev/ad0s1b.eli		none		swap	sw		0	0</programlisting>

      <para>By default, &man.geli.8; uses the <acronym>AES</acronym>
	algorithm with a key length of 128 bit.  These defaults can be
	altered by using <literal>geli_swap_flags</literal> in
	<filename>/etc/rc.conf</filename>.  The following flags
	configure encryption using the Blowfish algorithm with a key
	length of 128 bits and a sectorsize of 4 kilobytes, and sets
	<quote>detach on last close</quote>:</para>

      <programlisting>geli_swap_flags="-e blowfish -l 128 -s 4096 -d"</programlisting>

      <para>Refer to the description of <literal>onetime</literal> in
	&man.geli.8; for a list of possible options.</para>
    </sect2>

    <sect2>
      <title>Encrypted Swap Verification</title>

      <para>Once the system has rebooted, proper operation of the
	encrypted swap can be verified using
	<command>swapinfo</command>.</para>

      <para>If &man.gbde.8; is being used:</para>

      <screen>&prompt.user; <userinput>swapinfo</userinput>
Device          1K-blocks     Used    Avail Capacity
/dev/ad0s1b.bde    542720        0   542720     0%</screen>

      <para>If &man.geli.8; is being used:</para>

      <screen>&prompt.user; <userinput>swapinfo</userinput>
Device          1K-blocks     Used    Avail Capacity
/dev/ad0s1b.eli    542720        0   542720     0%</screen>
    </sect2>
  </sect1>

  <sect1 xml:id="disks-hast">
    <info>
      <title>Highly Available Storage
	(<acronym>HAST</acronym>)</title>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Daniel</firstname>
	    <surname>Gerzo</surname>
	  </personname>
	  <contrib>Contributed by </contrib>
	</author>
      </authorgroup>

      <authorgroup>
	<author>
	  <personname>
	    <firstname>Freddie</firstname>
	    <surname>Cash</surname>
	  </personname>
	  <contrib>With inputs from </contrib>
	</author>

	<author>
	  <personname>
	    <firstname>Pawel Jakub</firstname>
	    <surname>Dawidek</surname>
	  </personname>
	</author>

	<author>
	  <personname>
	    <firstname>Michael W.</firstname>
	    <surname>Lucas</surname>
	  </personname>
	</author>

	<author>
	  <personname>
	    <firstname>Viktor</firstname>
	    <surname>Petersson</surname>
	  </personname>
	</author>
      </authorgroup>
    </info>

    <indexterm>
      <primary>HAST</primary>
      <secondary>high availability</secondary>
    </indexterm>

    <para>High availability is one of the main requirements in
      serious business applications and highly-available storage is a
      key component in such environments.  In &os;, the Highly
      Available STorage (<acronym>HAST</acronym>) framework allows
      transparent storage of the same data across several physically
      separated machines connected by a <acronym>TCP/IP</acronym>
      network.  <acronym>HAST</acronym> can be understood as a
      network-based RAID1 (mirror), and is similar to the DRBD&reg;
      storage system used in the GNU/&linux; platform.  In combination
      with other high-availability features of &os; like
      <acronym>CARP</acronym>, <acronym>HAST</acronym> makes it
      possible to build a highly-available storage cluster that is
      resistant to hardware failures.</para>

    <para>The following are the main features of
      <acronym>HAST</acronym>:</para>

    <itemizedlist>
      <listitem>
	<para>Can be used to mask <acronym>I/O</acronym> errors on
	  local hard drives.</para>
      </listitem>

      <listitem>
	<para>File system agnostic as it works with any file system
	  supported by &os;.</para>
      </listitem>

      <listitem>
	<para>Efficient and quick resynchronization as only the blocks
	  that were modified during the downtime of a node are
	  synchronized.</para>
      </listitem>

      <!--
      <listitem>
	<para>Has several synchronization modes to allow for fast
	  failover.</para>
      </listitem>
      -->

      <listitem>
	<para>Can be used in an already deployed environment to add
	  additional redundancy.</para>
      </listitem>

      <listitem>
	<para>Together with <acronym>CARP</acronym>,
	  <application>Heartbeat</application>, or other tools, it can
	  be used to build a robust and durable storage system.</para>
      </listitem>
    </itemizedlist>

    <para>After reading this section, you will know:</para>

    <itemizedlist>
      <listitem>
	<para>What <acronym>HAST</acronym> is, how it works, and
	  which features it provides.</para>
      </listitem>

      <listitem>
	<para>How to set up and use <acronym>HAST</acronym> on
	  &os;.</para>
      </listitem>

      <listitem>
	<para>How to integrate <acronym>CARP</acronym> and
	  &man.devd.8; to build a robust storage system.</para>
      </listitem>
    </itemizedlist>

    <para>Before reading this section, you should:</para>

    <itemizedlist>
      <listitem>
	<para>Understand &unix; and &os; basics (<xref
	    linkend="basics"/>).</para>
      </listitem>

      <listitem>
	<para>Know how to configure network
	  interfaces and other core &os; subsystems (<xref
	    linkend="config-tuning"/>).</para>
      </listitem>

      <listitem>
	<para>Have a good understanding of &os;
	  networking (<xref
	    linkend="network-communication"/>).</para>
      </listitem>
    </itemizedlist>

    <para>The <acronym>HAST</acronym> project was sponsored by The
      &os; Foundation with support from <link
	xlink:href="http://www.omc.net/">http://www.omc.net/</link>
      and <link
	xlink:href="http://www.transip.nl/">http://www.transip.nl/</link>.</para>

    <sect2>
      <title>HAST Operation</title>

      <para><acronym>HAST</acronym> provides synchronous block-level
	replication between two physical machines: the
	<emphasis>primary</emphasis>, also known as the
	<emphasis>master</emphasis> node, and the
	<emphasis>secondary</emphasis>, or <emphasis>slave</emphasis>
	node.  These two machines together are referred to as a
	cluster.</para>

      <para>Since <acronym>HAST</acronym> works in a primary-secondary
	configuration, it allows only one of the cluster nodes to be
	active at any given time.  The primary node, also called
	<emphasis>active</emphasis>, is the one which will handle all
	the <acronym>I/O</acronym> requests to
	<acronym>HAST</acronym>-managed devices.  The secondary node
	is automatically synchronized from the primary node.</para>

      <para>The physical components of the <acronym>HAST</acronym>
	system are the local disk on primary node, and the disk on the
	remote, secondary node.</para>

      <para><acronym>HAST</acronym> operates synchronously on a block
	level, making it transparent to file systems and applications.
	<acronym>HAST</acronym> provides regular GEOM providers in
	<filename>/dev/hast/</filename> for use by other tools or
	applications.  There is no difference between using
	<acronym>HAST</acronym>-provided devices and raw disks or
	partitions.</para>

      <para>Each write, delete, or flush operation is sent to both the
	local disk and to the remote disk over
	<acronym>TCP/IP</acronym>.  Each read operation is served from
	the local disk, unless the local disk is not up-to-date or an
	<acronym>I/O</acronym> error occurs.  In such cases, the read
	operation is sent to the secondary node.</para>

      <para><acronym>HAST</acronym> tries to provide fast failure
	recovery.  For this reason, it is important to reduce
	synchronization time after a node's outage.  To provide fast
	synchronization, <acronym>HAST</acronym> manages an on-disk
	bitmap of dirty extents and only synchronizes those during a
	regular synchronization, with an exception of the initial
	sync.</para>

      <para>There are many ways to handle synchronization.
	<acronym>HAST</acronym> implements several replication modes
	to handle different synchronization methods:</para>

      <itemizedlist>
	<listitem>
	  <para><emphasis>memsync</emphasis>: This mode reports a
	    write operation as completed when the local write
	    operation is finished and when the remote node
	    acknowledges data arrival, but before actually storing the
	    data.  The data on the remote node will be stored directly
	    after sending the acknowledgement.  This mode is intended
	    to reduce latency, but still provides good
	    reliability.</para>
	</listitem>

	<listitem>
	  <para><emphasis>fullsync</emphasis>: This mode reports a
	    write operation as completed when both the local write and
	    the remote write complete.  This is the safest and the
	    slowest replication mode.  This mode is the
	    default.</para>
	</listitem>

	<listitem>
	  <para><emphasis>async</emphasis>: This mode reports a write
	    operation as completed when the local write completes.
	    This is the fastest and the most dangerous replication
	    mode.  It should only be used when replicating to a
	    distant node where latency is too high for other
	    modes.</para>
	</listitem>
      </itemizedlist>
    </sect2>

    <sect2>
      <title>HAST Configuration</title>

      <para>The <acronym>HAST</acronym> framework consists of several
	components:</para>

      <itemizedlist>
	<listitem>
	  <para>The &man.hastd.8; daemon which provides data
	    synchronization.  When this daemon is started, it will
	    automatically load <varname>geom_gate.ko</varname>.</para>
	</listitem>

	<listitem>
	  <para>The userland management utility,
	    &man.hastctl.8;.</para>
	</listitem>

	<listitem>
	  <para>The &man.hast.conf.5; configuration file.  This file
	    must exist before starting
	    <application>hastd</application>.</para>
	</listitem>
      </itemizedlist>

      <para>Users who prefer to statically build
	<literal>GEOM_GATE</literal> support into the kernel should
	add this line to the custom kernel configuration file, then
	rebuild the kernel using the instructions in <xref
	  linkend="kernelconfig"/>:</para>

      <programlisting>options	GEOM_GATE</programlisting>

      <para>The following example describes how to configure two nodes
	in master-slave/primary-secondary operation using
	<acronym>HAST</acronym> to replicate the data between the two.
	The nodes will be called <literal>hasta</literal>, with an
	<acronym>IP</acronym> address of
	<literal>172.16.0.1</literal>, and <literal>hastb</literal>,
	with an <acronym>IP</acronym> address of
	<literal>172.16.0.2</literal>.  Both nodes will have a
	dedicated hard drive <filename>/dev/ad6</filename> of the same
	size for <acronym>HAST</acronym> operation.  The
	<acronym>HAST</acronym> pool, sometimes referred to as a
	resource or the <acronym>GEOM</acronym> provider in <filename
	  class="directory">/dev/hast/</filename>, will be called
	<literal>test</literal>.</para>

      <para>Configuration of <acronym>HAST</acronym> is done using
	<filename>/etc/hast.conf</filename>.  This file should be
	identical on both nodes.  The simplest configuration
	is:</para>

      <programlisting>resource <replaceable>test</replaceable> {
	on <replaceable>hasta</replaceable> {
		local <replaceable>/dev/ad6</replaceable>
		remote <replaceable>172.16.0.2</replaceable>
	}
	on <replaceable>hastb</replaceable> {
		local <replaceable>/dev/ad6</replaceable>
		remote <replaceable>172.16.0.1</replaceable>
	}
}</programlisting>

      <para>For more advanced configuration, refer to
	&man.hast.conf.5;.</para>

      <tip>
	<para>It is also possible to use host names in the
	  <literal>remote</literal> statements if the hosts are
	  resolvable and defined either in
	  <filename>/etc/hosts</filename> or in the local
	  <acronym>DNS</acronym>.</para>
      </tip>

      <para>Once the configuration exists on both nodes, the
	<acronym>HAST</acronym> pool can be created.  Run these
	commands on both nodes to place the initial metadata onto the
	local disk and to start &man.hastd.8;:</para>

      <screen>&prompt.root; <userinput>hastctl create <replaceable>test</replaceable></userinput>
&prompt.root; <userinput>service hastd onestart</userinput></screen>

      <note>
	<para>It is <emphasis>not</emphasis> possible to use
	  <acronym>GEOM</acronym>
	  providers with an existing file system or to convert an
	  existing storage to a <acronym>HAST</acronym>-managed pool.
	  This procedure needs to store some metadata on the provider
	  and there will not be enough required space available on an
	  existing provider.</para>
      </note>

      <para>A HAST node's <literal>primary</literal> or
	<literal>secondary</literal> role is selected by an
	administrator, or software like
	<application>Heartbeat</application>, using &man.hastctl.8;.
	On the primary node, <literal>hasta</literal>, issue this
	command:</para>

      <screen>&prompt.root; <userinput>hastctl role primary <replaceable>test</replaceable></userinput></screen>

      <para>Run this command on the secondary node,
	<literal>hastb</literal>:</para>

      <screen>&prompt.root; <userinput>hastctl role secondary <replaceable>test</replaceable></userinput></screen>

      <para>Verify the result by running <command>hastctl</command> on
	each node:</para>

      <screen>&prompt.root; <userinput>hastctl status <replaceable>test</replaceable></userinput></screen>

      <para>Check the <literal>status</literal> line in the output.
	If it says <literal>degraded</literal>, something is wrong
	with the configuration file.  It should say
	<literal>complete</literal> on each node, meaning that the
	synchronization between the nodes has started.  The
	synchronization completes when <command>hastctl
	  status</command> reports 0 bytes of <literal>dirty</literal>
	extents.</para>

      <para>The next step is to create a file system on the
	<acronym>GEOM</acronym> provider and mount it.  This must be
	done on the <literal>primary</literal> node.  Creating the
	file system can take a few minutes, depending on the size of
	the hard drive.  This example creates a <acronym>UFS</acronym>
	file system on <filename>/dev/hast/test</filename>:</para>

      <screen>&prompt.root; <userinput>newfs -U /dev/hast/<replaceable>test</replaceable></userinput>
&prompt.root; <userinput>mkdir /hast/<replaceable>test</replaceable></userinput>
&prompt.root; <userinput>mount /dev/hast/<replaceable>test</replaceable> <replaceable>/hast/test</replaceable></userinput></screen>

      <para>Once the <acronym>HAST</acronym> framework is configured
	properly, the final step is to make sure that
	<acronym>HAST</acronym> is started automatically during
	system boot.  Add this line to
	<filename>/etc/rc.conf</filename>:</para>

      <programlisting>hastd_enable="YES"</programlisting>

      <sect3>
	<title>Failover Configuration</title>

	<para>The goal of this example is to build a robust storage
	  system which is resistant to the failure of any given node.
	  If the primary node fails, the secondary node is there to
	  take over seamlessly, check and mount the file system, and
	  continue to work without missing a single bit of
	  data.</para>

	<para>To accomplish this task, the Common Address Redundancy
	  Protocol (<acronym>CARP</acronym>) is used to provide for
	  automatic failover at the <acronym>IP</acronym> layer.
	  <acronym>CARP</acronym> allows multiple hosts on the same
	  network segment to share an <acronym>IP</acronym> address.
	  Set up <acronym>CARP</acronym> on both nodes of the cluster
	  according to the documentation available in <xref
	    linkend="carp"/>.  In this example, each node will have
	  its own management <acronym>IP</acronym> address and a
	  shared <acronym>IP</acronym> address of
	  <replaceable>172.16.0.254</replaceable>.  The primary
	  <acronym>HAST</acronym> node of the cluster must be the
	  master <acronym>CARP</acronym> node.</para>

	<para>The <acronym>HAST</acronym> pool created in the previous
	  section is now ready to be exported to the other hosts on
	  the network.  This can be accomplished by exporting it
	  through <acronym>NFS</acronym> or
	  <application>Samba</application>, using the shared
	  <acronym>IP</acronym> address
	  <replaceable>172.16.0.254</replaceable>.  The only problem
	  which remains unresolved is an automatic failover should the
	  primary node fail.</para>

	<para>In the event of <acronym>CARP</acronym> interfaces going
	  up or down, the &os; operating system generates a
	  &man.devd.8; event, making it possible to watch for state
	  changes on the <acronym>CARP</acronym> interfaces.  A state
	  change on the <acronym>CARP</acronym> interface is an
	  indication that one of the nodes failed or came back online.
	  These state change events make it possible to run a script
	  which will automatically handle the HAST failover.</para>

	<para>To catch state changes on the
	  <acronym>CARP</acronym> interfaces, add this configuration
	  to <filename>/etc/devd.conf</filename> on each node:</para>

	<programlisting>notify 30 {
	match "system" "IFNET";
	match "subsystem" "carp0";
	match "type" "LINK_UP";
	action "/usr/local/sbin/carp-hast-switch master";
};

notify 30 {
	match "system" "IFNET";
	match "subsystem" "carp0";
	match "type" "LINK_DOWN";
	action "/usr/local/sbin/carp-hast-switch slave";
};</programlisting>

	<note>
	  <para>If the systems are running &os;&nbsp;10 or higher,
	    replace <filename>carp0</filename> with the name of the
	    <acronym>CARP</acronym>-configured interface.</para>
	</note>

	<para>Restart &man.devd.8; on both nodes to put the new
	  configuration into effect:</para>

	<screen>&prompt.root; <userinput>service devd restart</userinput></screen>

	<para>When the specified interface state changes by going up
	  or down , the system generates a notification, allowing the
	  &man.devd.8; subsystem to run the specified automatic
	  failover script,
	  <filename>/usr/local/sbin/carp-hast-switch</filename>.
	  For further clarification about this configuration, refer to
	  &man.devd.conf.5;.</para>

	<para>Here is an example of an automated failover
	  script:</para>

	<programlisting>#!/bin/sh

# Original script by Freddie Cash &lt;fjwcash@gmail.com&gt;
# Modified by Michael W. Lucas &lt;mwlucas@BlackHelicopters.org&gt;
# and Viktor Petersson &lt;vpetersson@wireload.net&gt;

# The names of the HAST resources, as listed in /etc/hast.conf
resources="<replaceable>test</replaceable>"

# delay in mounting HAST resource after becoming master
# make your best guess
delay=3

# logging
log="local0.debug"
name="carp-hast"

# end of user configurable stuff

case "$1" in
	master)
		logger -p $log -t $name "Switching to primary provider for ${resources}."
		sleep ${delay}

		# Wait for any "hastd secondary" processes to stop
		for disk in ${resources}; do
			while $( pgrep -lf "hastd: ${disk} \(secondary\)" &gt; /dev/null 2&gt;&amp;1 ); do
				sleep 1
			done

			# Switch role for each disk
			hastctl role primary ${disk}
			if [ $? -ne 0 ]; then
				logger -p $log -t $name "Unable to change role to primary for resource ${disk}."
				exit 1
			fi
		done

		# Wait for the /dev/hast/* devices to appear
		for disk in ${resources}; do
			for I in $( jot 60 ); do
				[ -c "/dev/hast/${disk}" ] &amp;&amp; break
				sleep 0.5
			done

			if [ ! -c "/dev/hast/${disk}" ]; then
				logger -p $log -t $name "GEOM provider /dev/hast/${disk} did not appear."
				exit 1
			fi
		done

		logger -p $log -t $name "Role for HAST resources ${resources} switched to primary."


		logger -p $log -t $name "Mounting disks."
		for disk in ${resources}; do
			mkdir -p /hast/${disk}
			fsck -p -y -t ufs /dev/hast/${disk}
			mount /dev/hast/${disk} /hast/${disk}
		done

	;;

	slave)
		logger -p $log -t $name "Switching to secondary provider for ${resources}."

		# Switch roles for the HAST resources
		for disk in ${resources}; do
			if ! mount | grep -q "^/dev/hast/${disk} on "
			then
			else
				umount -f /hast/${disk}
			fi
			sleep $delay
			hastctl role secondary ${disk} 2&gt;&amp;1
			if [ $? -ne 0 ]; then
				logger -p $log -t $name "Unable to switch role to secondary for resource ${disk}."
				exit 1
			fi
			logger -p $log -t $name "Role switched to secondary for resource ${disk}."
		done
	;;
esac</programlisting>

	<para>In a nutshell, the script takes these actions when a
	  node becomes master:</para>

	<itemizedlist>
	  <listitem>
	    <para>Promotes the <acronym>HAST</acronym> pool to
	      primary on the other node.</para>
	  </listitem>

	  <listitem>
	    <para>Checks the file system under the
	      <acronym>HAST</acronym> pool.</para>
	  </listitem>

	  <listitem>
	    <para>Mounts the pool.</para>
	  </listitem>
	</itemizedlist>

	<para>When a node becomes secondary:</para>

	<itemizedlist>
	  <listitem>
	    <para>Unmounts the <acronym>HAST</acronym> pool.</para>
	  </listitem>

	  <listitem>
	    <para>Degrades the <acronym>HAST</acronym> pool to
	      secondary.</para>
	  </listitem>
	</itemizedlist>

	<caution>
	  <para>This is just an example script which serves as a proof
	    of concept.  It does not handle all the possible scenarios
	    and can be extended or altered in any way, for example, to
	    start or stop required services.</para>
	</caution>

	<tip>
	  <para>For this example, a standard <acronym>UFS</acronym>
	    file system was used.  To reduce the time needed for
	    recovery, a journal-enabled <acronym>UFS</acronym> or
	    <acronym>ZFS</acronym> file system can be used
	    instead.</para>
	</tip>

	<para>More detailed information with additional examples can
	  be found at <link
	    xlink:href="http://wiki.FreeBSD.org/HAST">http://wiki.FreeBSD.org/HAST</link>.</para>
      </sect3>
    </sect2>

    <sect2>
      <title>Troubleshooting</title>

      <para><acronym>HAST</acronym> should generally work without
	issues.  However, as with any other software product, there
	may be times when it does not work as supposed.  The sources
	of the problems may be different, but the rule of thumb is to
	ensure that the time is synchronized between the nodes of the
	cluster.</para>

      <para>When troubleshooting <acronym>HAST</acronym>, the
	debugging level of &man.hastd.8; should be increased by
	starting <command>hastd</command> with <literal>-d</literal>.
	This argument may be specified multiple times to further
	increase the debugging level.  Consider also using
	<literal>-F</literal>, which starts <command>hastd</command>
	in the foreground.</para>

      <sect3 xml:id="disks-hast-sb">
	<title>Recovering from the Split-brain Condition</title>

	<para><firstterm>Split-brain</firstterm> occurs when the nodes
	  of the cluster are unable to communicate with each other,
	  and both are configured as primary.  This is a dangerous
	  condition because it allows both nodes to make incompatible
	  changes to the data.  This problem must be corrected
	  manually by the system administrator.</para>

	<para>The administrator must decide which node has more
	  important changes or merge them manually.  Then, let
	  <acronym>HAST</acronym> perform full synchronization of the
	  node which has the broken data.  To do this, issue these
	  commands on the node which needs to be
	  resynchronized:</para>

	<screen>&prompt.root; <userinput>hastctl role init <replaceable>test</replaceable></userinput>
&prompt.root; <userinput>hastctl create <replaceable>test</replaceable></userinput>
&prompt.root; <userinput>hastctl role secondary <replaceable>test</replaceable></userinput></screen>
      </sect3>
    </sect2>
  </sect1>
</chapter>