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diff --git a/el_GR.ISO8859-7/books/handbook/filesystems/chapter.sgml b/el_GR.ISO8859-7/books/handbook/filesystems/chapter.sgml new file mode 100644 index 0000000000..18d6e92a6d --- /dev/null +++ b/el_GR.ISO8859-7/books/handbook/filesystems/chapter.sgml @@ -0,0 +1,630 @@ +<!-- + + Το Εγχειρίδιο του FreeBSD: Συστήματα Αρχείων + + The FreeBSD Greek Documentation Project + + $FreeBSD$ + + %SOURCE% en_US.ISO8859-1/books/handbook/filesystems/chapter.sgml + %SRCID% 1.3 + +--> + +<chapter id="filesystems"> + <chapterinfo> + <authorgroup> + <author> + <firstname>Tom</firstname> + <surname>Rhodes</surname> + <contrib>Γράφηκε από τον </contrib> + </author> + </authorgroup> + </chapterinfo> + + <title>Υποστήριξη Συστημάτων Αρχείων</title> + + <sect1 id="filesystems-synopsis"> + <title>Σύνοψη</title> + + <indexterm><primary>File Systems</primary></indexterm> + <indexterm> + <primary>File Systems Support</primary> + <see>File Systems</see> + </indexterm> + + <para>Τα συστήματα αρχείων αποτελούν αναπόσπαστο τμήμα κάθε λειτουργικού + συστήματος. Επιτρέπουν στους χρήστες να δημιουργούν και να αποθηκεύουν + αρχεία, παρέχουν πρόσβαση σε δεδομένα, και φυσικά αξιοποιούν τους + σκληρούς δίσκους. Διαφορετικά λειτουργικά συστήματα χρησιμοποιούν + συνήθως διαφορετικά εγγενή συστήματα αρχείων. Το σύστημα αρχείων του + &os; είναι το Fast File System ή <acronym>FFS</acronym>, το + οποίο προήλθε από το αρχικό σύστημα αρχείων του Unix™, γνωστό + επίσης και ως <acronym>UFS</acronym>. Αυτό είναι και το εγγενές + σύστημα αρχείων του &os;, το οποίο χρησιμοποιείται στους σκληρούς + δίσκους και προσφέρει πρόσβαση στα δεδομένα.</para> + + <para>Το &os; προσφέρει επίσης πληθώρα διαφορετικών συστημάτων αρχείων, + ώστε να παρέχει τοπική πρόσβαση σε δεδομένα που έχουν δημιουργηθεί από + άλλα λειτουργικά συστήματα, π.χ. δεδομένα που βρίσκονται σε τοπικά + <acronym>USB</acronym> αποθηκευτικά μέσα, οδηγούς flash, και σκληρούς + δίσκους. Υπάρχει επίσης υποστήριξη για άλλα, μη-εγγενή συστήματα + αρχείων, όπως το το Extended File System (<acronym>EXT</acronym>) του + &linux; καθώς και το σύστημα Z File System (<acronym>ZFS</acronym>) της + &sun;.</para> + + <para>Το &os; παρέχει διαφορετικό επίπεδο υποστήριξης για κάθε σύστημα + αρχείων. Για ορισμένα θα χρειαστεί να φορτωθεί κάποιο άρθρωμα στον + πυρήνα, ενώ για άλλα θα πρέπει να εγκατασταθούν κάποια εργαλεία. + Το κεφάλαιο αυτό έχει σχεδιαστεί να βοηθήσει τους χρήστες του &os; να + αποκτήσουν πρόσβαση σε άλλα συστήματα αρχείων στο σύστημα τους, + ξεκινώντας από το Ζ File System της &sun;.</para> + + <para>Αφού διαβάσετε αυτό το κεφάλαιο, θα γνωρίζετε:</para> + + <itemizedlist> + <listitem> + <para>Τη διαφορά μεταξύ των εγγενών και των υποστηριζόμενων + συστημάτων αρχείων.</para> + </listitem> + + <listitem> + <para>Ποια συστήματα αρχείων υποστηρίζονται από το &os;.</para> + </listitem> + + <listitem> + <para>Πως να ενεργοποιήσετε, να ρυθμίσετε, να αποκτήσετε πρόσβαση και + να χρησιμοποιήσετε μη-εγγενή συστήματα αρχείων.</para> + </listitem> + </itemizedlist> + + <para>Πριν διαβάσετε αυτό το κεφάλαιο, θα πρέπει:</para> + + <itemizedlist> + <listitem> + <para>Να κατανοείτε βασικές έννοιες του &unix; και του &os; + (<xref linkend="basics">).</para> + </listitem> + + <listitem> + <para>Να είστε εξοικειωμένος με τις βασικές διαδικασίες ρύθμισης και + εγκατάστασης προσαρμοσμένου πυρήνα + (<xref linkend="kernelconfig">).</para> + </listitem> + + <listitem> + <para>Να αισθάνεστε άνετα με την εγκατάσταση εφαρμογών τρίτου + κατασκευαστή στο &os; (<xref linkend="ports">).</para> + </listitem> + + <listitem> + <para>Να είστε εξοικειωμένος με τους δίσκους, τα μέσα + αποθήκευσης, και τα αντίστοιχα ονόματα συσκευών στο + &os; (<xref linkend="disks">).</para> + </listitem> + </itemizedlist> + + <!-- + Temporary warning to avoid listing experimental versions + and production versions of FreeBSD with this technology. + --> + <warning> + <para>Τη δεδομένη στιγμή, το <acronym>ZFS</acronym> θεωρείται + δοκιμαστική δυνατότητα. Μερικές επιλογές μπορεί να υπολείπονται + λειτουργικότητας, και άλλες μπορεί να μη λειτουργούν καθόλου. Με + την πάροδο του χρόνου, η δυνατότητα αυτή θα θεωρηθεί έτοιμη για χρήση + σε περιβάλλοντα παραγωγής, και η παρούσα τεκμηρίωση θα ανανεωθεί ώστε + να αντιπροσωπεύει αυτή την κατάσταση.</para> + </warning> + </sect1> + + <sect1 id="filesystems-zfs"> + <title>The Z File System</title> + + <para>The Z file system, developed by &sun;, is a new + technology designed to use a pooled storage method. This means + that space is only used as it is needed for data storage. It + has also been designed for maximum data integrity, supporting + data snapshots, multiple copies, and data checksums. A new + data replication model, known as <acronym>RAID</acronym>-Z has + been added. The <acronym>RAID</acronym>-Z model is similar + to <acronym>RAID</acronym>5 but is designed to prevent data + write corruption.</para> + + <sect2> + <title>ZFS Tuning</title> + + <para>The <acronym>ZFS</acronym> subsystem utilizes much of + the system resources, so some tuning may be required to provide + maximum efficiency during every-day use. As an experimental + feature in &os; this may change in the near future; however, + at this time, the following steps are recommended.</para> + + <sect3> + <title>Memory</title> + + <para>The total system memory should be at least one gigabyte, + with two gigabytes or more recommended. In all of the + examples here, the system has one gigabyte of memory with + several other tuning mechanisms in place.</para> + + <para>Some people have had luck using fewer than one gigabyte + of memory, but with such a limited amount of physical memory, + when the system is under heavy load, it is very plausible + that &os; will panic due to memory exhaustion.</para> + </sect3> + + <sect3> + <title>Kernel Configuration</title> + + <para>It is recommended that unused drivers and options + be removed from the kernel configuration file. Since most + devices are available as modules, they may simply be loaded + using the <filename>/boot/loader.conf</filename> file.</para> + + <para>Users of the i386 architecture should add the following + option to their kernel configuration file, rebuild their + kernel, and reboot:</para> + + <programlisting>options KVA_PAGES=512</programlisting> + + <para>This option will expand the kernel address space, thus + allowing the <varname>vm.kvm_size</varname> tunable to be + pushed beyond the currently imposed limit of 1 GB + (2 GB for <acronym>PAE</acronym>). To find the most + suitable value for this option, divide the desired address + space in megabytes by four (4). In this case, it is + <literal>512</literal> for 2 GB.</para> + </sect3> + + <sect3> + <title>Loader Tunables</title> + + <para>The <devicename>kmem</devicename> address space should be + increased on all &os; architectures. On the test system with + one gigabyte of physical memory, success was achieved with the + following options which should be placed in + the <filename>/boot/loader.conf</filename> file and the system + restarted:</para> + + <programlisting>vm.kmem_slze="330M" +vm.kmem_size_max="330M" +vfs.zfs.arc_max="40M" +vfs.zfs.vdev.cache.size="5M"</programlisting> + + <para>For a more detailed list of recommendations for ZFS-related + tuning, see + <ulink url="http://wiki.freebsd.org/ZFSTuningGuide"></ulink>.</para> + </sect3> + </sect2> + + <sect2> + <title>Using <acronym>ZFS</acronym></title> + + <para>There is a start up mechanism that allows &os; to + mount <acronym>ZFS</acronym> pools during system + initialization. To set it, issue the following + commands:</para> + + <screen>&prompt.root; <userinput>echo 'zfs_enable="YES"' >> /etc/rc.conf</userinput> +&prompt.root; <userinput>/etc/rc.d/zfs start</userinput></screen> + + <para>The remainder of this document assumes two + <acronym>SCSI</acronym> disks are available, and their device names + are <devicename><replaceable>da0</replaceable></devicename> + and <devicename><replaceable>da1</replaceable></devicename> + respectively. Users of <acronym>IDE</acronym> hardware may + use the <devicename><replaceable>ad</replaceable></devicename> + devices in place of <acronym>SCSI</acronym> hardware.</para> + + <sect3> + <title>Single Disk Pool</title> + + <para>To create a <acronym>ZFS</acronym> over a single disk + device, use the <command>zpool</command> command:</para> + + <screen>&prompt.root; <userinput>zpool create example /dev/da0</userinput></screen> + + <para>To view the new pool, review the output of the + <command>df</command>:</para> + + <screen>&prompt.root; <userinput>df</userinput> +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235230 1628718 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032846 48737598 2% /usr +example 17547136 0 17547136 0% /example</screen> + + <para>This output clearly shows the <literal>example</literal> + pool has not only been created but + <emphasis>mounted</emphasis> as well. It is also accessible + just like a normal file system, files may be created on it + and users are able to browse it as in the + following example:</para> + + <screen>&prompt.root <userinput>cd /example</userinput> +&prompt.root; <userinput>ls</userinput> +&prompt.root; <userinput>touch testfile</userinput> +&prompt.root; <userinput>ls -al</userinput> +total 4 +drwxr-xr-x 2 root wheel 3 Aug 29 23:15 . +drwxr-xr-x 21 root wheel 512 Aug 29 23:12 .. +-rw-r--r-- 1 root wheel 0 Aug 29 23:15 testfile</screen> + + <para>Unfortunately this pool is not taking advantage of + any <acronym>ZFS</acronym> features. Create a file system + on this pool, and enable compression on it:</para> + + <screen>&prompt.root; <userinput>zfs create example/compressed</userinput> +&prompt.root; <userinput>zfs set compression=gzip example/compressed</userinput></screen> + + <para>The <literal>example/compressed</literal> is now a + <acronym>ZFS</acronym> compressed file system. Try copying + some large files to it by copying them to + <filename class="directory">/example/compressed</filename>.</para> + + <para>The compression may now be disabled with:</para> + + <screen>&prompt.root; <userinput>zfs set compression=off example/compressed</userinput></screen> + + <para>To unmount the file system, issue the following command + and then verify by using the <command>df</command> + utility:</para> + + <screen>&prompt.root; <userinput>zfs umount example/compressed</userinput> +&prompt.root; <userinput>df</userinput> +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235232 1628716 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032864 48737580 2% /usr +example 17547008 0 17547008 0% /example</screen> + + <para>Re-mount the file system to make it accessible + again, and verify with <command>df</command>:</para> + + <screen>&prompt.root; <userinput>zfs mount example/compressed</userinput> +&prompt.root; <userinput>df</userinput> +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235234 1628714 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032864 48737580 2% /usr +example 17547008 0 17547008 0% /example +example/compressed 17547008 0 17547008 0% /example/compressed</screen> + + <para>The pool and file system may also be observed by viewing + the output from <command>mount</command>:</para> + + <screen>&prompt.root; <userinput>mount</userinput> +/dev/ad0s1a on / (ufs, local) +devfs on /dev (devfs, local) +/dev/ad0s1d on /usr (ufs, local, soft-updates) +example on /example (zfs, local) +example/data on /example/data (zfs, local) +example/compressed on /example/compressed (zfs, local)</screen> + + <para>As observed, <acronym>ZFS</acronym> file systems, after + creation, may be used like ordinary file systems; however, + many other features are also available. In the following + example, a new file system, <literal>data</literal> is + created. Important files will be stored here, so the file + system is set to keep two copies of each data block:</para> + + <screen>&prompt.root; <userinput>zfs create example/data</userinput> +&prompt.root; <userinput>zfs set copies=2 example/data</userinput></screen> + + <para>It is now possible to see the data and space utilization + by issuing the <command>df</command> again:</para> + + <screen>&prompt.root; <userinput>df</userinput> +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235234 1628714 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032864 48737580 2% /usr +example 17547008 0 17547008 0% /example +example/compressed 17547008 0 17547008 0% /example/compressed +example/data 17547008 0 17547008 0% /example/data</screen> + + <para>Notice that each file system on the pool has the same + amount of available space. This is the reason for using + the <command>df</command> through these examples, to show + that the file systems are using only the amount of space + they need and will all draw from the same pool. + The <acronym>ZFS</acronym> file system does away with concepts + such as volumes and partitions, and allows for several file + systems to occupy the same pool. Destroy the file systems, + and then destroy the pool as they are no longer + needed:</para> + + <screen>&prompt.root; <userinput>zfs destroy example/compressed</userinput> +&prompt.root; <userinput>zfs destroy example/data</userinput> +&prompt.root; <userinput>zpool destroy example</userinput></screen> + + <para>Disks go bad and fail, an unavoidable trait. When + this disk goes bad, the data will be lost. One method of + avoiding data loss due to a failed hard disk is to implement + a <acronym>RAID</acronym>. <acronym>ZFS</acronym> supports + this feature in its pool design which is covered in + the next section.</para> + </sect3> + + <sect3> + <title><acronym>ZFS</acronym> RAID-Z</title> + + <para>As previously noted, this section will assume that + two <acronym>SCSI</acronym> exists as devices + <devicename>da0</devicename> and + <devicename>da1</devicename>. To create a + <acronym>RAID</acronym>-Z pool, issue the following + command:</para> + + <screen>&prompt.root; <userinput>zpool create storage raidz da0 da1</userinput></screen> + + <para>The <literal>storage</literal> zpool should have been + created. This may be verified by using the &man.mount.8; and + &man.df.1; commands as before. More disk devices may have + been allocated by adding them to the end of the list above. + Make a new file system in the pool, called + <literal>home</literal> where user files will eventually be + placed:</para> + + <screen>&prompt.root; <userinput>zfs create storage/home</userinput></screen> + + <para>It is now possible to enable compression and keep extra + copies of the user's home directories and files. This may + be accomplished just as before using the following + commands:</para> + + <screen>&prompt.root; <userinput>zfs set copies=2 storage/home</userinput> +&prompt.root; <userinput>zfs set compression=gzip storage/home</userinput></screen> + + <para>To make this the new home directory for users, copy the + user data to this directory, and create the appropriate + symbolic links:</para> + + <screen>&prompt.root; <userinput>cp -rp /home/* /storage/home</userinput> +&prompt.root; <userinput>rm -rf /home /usr/home</userinput> +&prompt.root; <userinput>ln -s /storage/home /home</userinput> +&prompt.root; <userinput>ln -s /storage/home /usr/home</userinput></screen> + + <para>Users should now have their data stored on the freshly + created <filename class="directory">/storage/home</filename> + file system. Test by adding a new user and logging in as + that user.</para> + + <para>Try creating a snapshot which may be rolled back + later:</para> + + <screen>&prompt.root; <userinput>zfs snapshot storage/home@08-30-08</userinput></screen> + + <para>Note that the snapshot option will only capture a real + file system, not a home directory or a file. The + <literal>@</literal> character is a delimiter used between + the file system name or the volume name. When a user's + home directory gets trashed, restore it with:</para> + + <screen>&prompt.root; <userinput>zfs rollback storage/home@08-30-08</userinput></screen> + + <para>To get a list of all available snapshots, run the + <command>ls</command> in the file system's + <filename class="directory">.zfs/snapshot</filename> + directory. For example, to see the previously taken + snapshot, perform the following command:</para> + + <screen>&prompt.root; <userinput>ls /storage/home/.zfs/snapshot</userinput></screen> + + <para>It is possible to write a script to perform monthly + snapshots on user data; however, over time, snapshots + may consume a great deal of disk space. The previous + snapshot may be removed using the following command:</para> + + <screen>&prompt.root; <userinput>zfs destroy storage/home@08-30-08</userinput></screen> + + <para>There is no reason, after all of this testing, we should + keep <filename class="directory">/storage/home</filename> + around in its present state. Make it the real + <filename class="directory">/home</filename> file + system:</para> + + <screen>&prompt.root; <userinput>zfs set mountpoint=/home storage/home</userinput></screen> + + <para>Issuing the <command>df</command> and + <command>mount</command> commands will show that the system + now treats our file system as the real + <filename class="directory">/home</filename>:</para> + + <screen>&prompt.root; <userinput>mount</userinput> +/dev/ad0s1a on / (ufs, local) +devfs on /dev (devfs, local) +/dev/ad0s1d on /usr (ufs, local, soft-updates) +storage on /storage (zfs, local) +storage/home on /home (zfs, local) +&prompt.root; <userinput>df</userinput> +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235240 1628708 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032826 48737618 2% /usr +storage 17547008 0 17547008 0% /storage +storage/home 17547008 0 17547008 0% /home</screen> + + <para>This completes the <acronym>RAID</acronym>-Z + configuration. To get status updates about the file systems + created during the nightly &man.periodic.8; runs, issue the + following command:</para> + + <screen>&prompt.root; <userinput>echo 'daily_status_zfs_enable="YES"' >> /etc/periodic.conf</userinput></screen> + </sect3> + + <sect3> + <title>Recovering <acronym>RAID</acronym>-Z</title> + + <para>Every software <acronym>RAID</acronym> has a method of + monitoring their <literal>state</literal>. + <acronym>ZFS</acronym> is no exception. The status of + <acronym>RAID</acronym>-Z devices may be viewed with the + following command:</para> + + <screen>&prompt.root; <userinput>zpool status -x</userinput></screen> + + <para>If all pools are healthy and everything is normal, the + following message will be returned:</para> + + <screen>all pools are healthy</screen> + + <para>If there is an issue, perhaps a disk has gone offline, + the pool state will be returned and look similar to:</para> + + <screen> pool: storage + state: DEGRADED +status: One or more devices has been taken offline by the administrator. + Sufficient replicas exist for the pool to continue functioning in a + degraded state. +action: Online the device using 'zpool online' or replace the device with + 'zpool replace'. + scrub: none requested +config: + + NAME STATE READ WRITE CKSUM + storage DEGRADED 0 0 0 + raidz1 DEGRADED 0 0 0 + da0 ONLINE 0 0 0 + da1 OFFLINE 0 0 0 + +errors: No known data errors</screen> + + <para>This states that the device was taken offline by the + administrator. This is true for this particular example. + To take the disk offline, the following command was + used:</para> + + <screen>&prompt.root; <userinput>zpool offline storage da1</userinput></screen> + + <para>It is now possible to replace the + <devicename>da1</devicename> after the system has been + powered down. When the system is back online, the following + command may issued to replace the disk:</para> + + <screen>&prompt.root; <userinput>zpool replace storage da1</userinput></screen> + + <para>From here, the status may be checked again, this time + without the <option>-x</option> flag to get state + information:</para> + + <screen>&prompt.root; <userinput>zpool status storage</userinput> + pool: storage + state: ONLINE + scrub: resilver completed with 0 errors on Sat Aug 30 19:44:11 2008 +config: + + NAME STATE READ WRITE CKSUM + storage ONLINE 0 0 0 + raidz1 ONLINE 0 0 0 + da0 ONLINE 0 0 0 + da1 ONLINE 0 0 0 + +errors: No known data errors</screen> + + <para>As shown from this example, everything appears to be + normal.</para> + </sect3> + + <sect3> + <title>Data Verification</title> + + <para>As previously mentioned, <acronym>ZFS</acronym> uses + <literal>checksums</literal> to verify the integrity of + stored data. They are enabled automatically upon creation + of file systems and may be disabled using the following + command:</para> + + <screen>&prompt.root; <userinput>zfs set checksum=off storage/home</userinput></screen> + + <para>This is not a wise idea; however, as checksums take + very little storage space and are more useful enabled. There + also appear to be no noticeable costs having them enabled. + While enabled, it is possible to have <acronym>ZFS</acronym> + check data integrity using checksum verification. This + process is known as <quote>scrubing.</quote> To verify the + data integrity of the <literal>storage</literal> pool, issue + the following command:</para> + + <screen>&prompt.root; <userinput>zpool scrub storage</userinput></screen> + + <para>This process may take considerable time depending on + the amount of data stored. It is also very + <acronym>I/O</acronym> intensive, so much that only one + of these operations may be run at any given time. After + the scrub has completed, the status is updated and may be + viewed by issuing a status request:</para> + + <screen>&prompt.root; <userinput>zpool status storage</userinput> + pool: storage + state: ONLINE + scrub: scrub completed with 0 errors on Sat Aug 30 19:57:37 2008 +config: + + NAME STATE READ WRITE CKSUM + storage ONLINE 0 0 0 + raidz1 ONLINE 0 0 0 + da0 ONLINE 0 0 0 + da1 ONLINE 0 0 0 + +errors: No known data errors</screen> + + <para>The completion time is in plain view in this example. + This feature helps to ensure data integrity over a long + period of time.</para> + + <para>There are many more options for the Z file system, + see the &man.zfs.8; and &man.zpool.8; manual + pages.</para> + </sect3> + </sect2> + </sect1> + + + <!-- + XXXTR: stub sections (added later, as needed, as desire, + after I get opinions from -doc people): + + Still need to discuss native and foreign file systems. + + <sect1> + <title>Device File System</title> + </sect1> + + <sect1> + <title>DOS and NTFS File Systems</title> + <para>This is a good section for those who transfer files, using + USB devices, from Windows to FreeBSD and vice-versa. My camera, + and many other cameras I have seen default to using FAT16. There + is (was?) a kde utility, I think called kamera, that could be used + to access camera devices. A section on this would be useful.</para> + + <para>XXXTR: Though! The disks chapter, covers a bit of this and + devfs under it's USB devices. It leaves a lot to be desired though, + see: +http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/usb-disks.html + It may be better to flesh out that section a bit more. Add the + word "camera" to it so that others can easily notice.</para> + </sect1> + + <sect1> + <title>Linux EXT File System</title> + + <para>Probably NOT as useful as the other two, but it requires + knowledge of the existence of the tools. Which are hidden in + the ports collection. Most Linux guys would probably only use + Linux, BSD guys would be smarter and use NFS.</para> + </sect1> + + <sect1> + <title>HFS</title> + + <para>I think this is the file system used on Apple OSX. There are + tools in the ports collection, and with Apple being a big + FreeBSD supporter and user of our technologies, surely there + is enough cross over to cover this?</para> + </sect1> + --> + +</chapter> |