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<div class="section" id="installing-kdcs">
<h1>Installing KDCs<a class="headerlink" href="#installing-kdcs" title="Permalink to this headline">¶</a></h1>
<p>When setting up Kerberos in a production environment, it is best to
have multiple slave KDCs alongside with a master KDC to ensure the
continued availability of the Kerberized services. Each KDC contains
a copy of the Kerberos database. The master KDC contains the writable
copy of the realm database, which it replicates to the slave KDCs at
regular intervals. All database changes (such as password changes)
are made on the master KDC. Slave KDCs provide Kerberos
ticket-granting services, but not database administration, when the
master KDC is unavailable. MIT recommends that you install all of
your KDCs to be able to function as either the master or one of the
slaves. This will enable you to easily switch your master KDC with
one of the slaves if necessary (see <a class="reference internal" href="#switch-master-slave"><em>Switching master and slave KDCs</em></a>). This
installation procedure is based on that recommendation.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<ul class="last simple">
<li>The Kerberos system relies on the availability of correct time
information. Ensure that the master and all slave KDCs have
properly synchronized clocks.</li>
<li>It is best to install and run KDCs on secured and dedicated
hardware with limited access. If your KDC is also a file
server, FTP server, Web server, or even just a client machine,
someone who obtained root access through a security hole in any
of those areas could potentially gain access to the Kerberos
database.</li>
</ul>
</div>
<div class="section" id="install-and-configure-the-master-kdc">
<h2>Install and configure the master KDC<a class="headerlink" href="#install-and-configure-the-master-kdc" title="Permalink to this headline">¶</a></h2>
<p>Install Kerberos either from the OS-provided packages or from the
source (See <a class="reference internal" href="../build/doing_build.html#do-build"><em>Building within a single tree</em></a>).</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p>For the purpose of this document we will use the following
names:</p>
<div class="highlight-python"><div class="highlight"><pre>kerberos.mit.edu - master KDC
kerberos-1.mit.edu - slave KDC
ATHENA.MIT.EDU - realm name
.k5.ATHENA.MIT.EDU - stash file
admin/admin - admin principal
</pre></div>
</div>
<p class="last">See <a class="reference internal" href="../mitK5defaults.html#mitk5defaults"><em>MIT Kerberos defaults</em></a> for the default names and locations
of the relevant to this topic files. Adjust the names and
paths to your system environment.</p>
</div>
</div>
<div class="section" id="edit-kdc-configuration-files">
<h2>Edit KDC configuration files<a class="headerlink" href="#edit-kdc-configuration-files" title="Permalink to this headline">¶</a></h2>
<p>Modify the configuration files, <a class="reference internal" href="conf_files/krb5_conf.html#krb5-conf-5"><em>krb5.conf</em></a> and
<a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><em>kdc.conf</em></a>, to reflect the correct information (such as
domain-realm mappings and Kerberos servers names) for your realm.
(See <a class="reference internal" href="../mitK5defaults.html#mitk5defaults"><em>MIT Kerberos defaults</em></a> for the recommended default locations for
these files).</p>
<p>Most of the tags in the configuration have default values that will
work well for most sites. There are some tags in the
<a class="reference internal" href="conf_files/krb5_conf.html#krb5-conf-5"><em>krb5.conf</em></a> file whose values must be specified, and this
section will explain those.</p>
<p>If the locations for these configuration files differs from the
default ones, set <strong>KRB5_CONFIG</strong> and <strong>KRB5_KDC_PROFILE</strong> environment
variables to point to the krb5.conf and kdc.conf respectively. For
example:</p>
<div class="highlight-python"><div class="highlight"><pre>export KRB5_CONFIG=/yourdir/krb5.conf
export KRB5_KDC_PROFILE=/yourdir/kdc.conf
</pre></div>
</div>
<div class="section" id="krb5-conf">
<h3>krb5.conf<a class="headerlink" href="#krb5-conf" title="Permalink to this headline">¶</a></h3>
<p>If you are not using DNS TXT records (see <a class="reference internal" href="realm_config.html#mapping-hostnames"><em>Mapping hostnames onto Kerberos realms</em></a>),
you must specify the <strong>default_realm</strong> in the <a class="reference internal" href="conf_files/krb5_conf.html#libdefaults"><em>[libdefaults]</em></a>
section. If you are not using DNS URI or SRV records (see
<a class="reference internal" href="realm_config.html#kdc-hostnames"><em>Hostnames for KDCs</em></a> and <a class="reference internal" href="realm_config.html#kdc-discovery"><em>KDC Discovery</em></a>), you must include the
<strong>kdc</strong> tag for each <em>realm</em> in the <a class="reference internal" href="conf_files/krb5_conf.html#realms"><em>[realms]</em></a> section. To
communicate with the kadmin server in each realm, the <strong>admin_server</strong>
tag must be set in the
<a class="reference internal" href="conf_files/krb5_conf.html#realms"><em>[realms]</em></a> section.</p>
<p>An example krb5.conf file:</p>
<div class="highlight-python"><div class="highlight"><pre>[libdefaults]
default_realm = ATHENA.MIT.EDU
[realms]
ATHENA.MIT.EDU = {
kdc = kerberos.mit.edu
kdc = kerberos-1.mit.edu
admin_server = kerberos.mit.edu
}
</pre></div>
</div>
</div>
<div class="section" id="kdc-conf">
<h3>kdc.conf<a class="headerlink" href="#kdc-conf" title="Permalink to this headline">¶</a></h3>
<p>The kdc.conf file can be used to control the listening ports of the
KDC and kadmind, as well as realm-specific defaults, the database type
and location, and logging.</p>
<p>An example kdc.conf file:</p>
<div class="highlight-python"><div class="highlight"><pre>[kdcdefaults]
kdc_listen = 88
kdc_tcp_listen = 88
[realms]
ATHENA.MIT.EDU = {
kadmind_port = 749
max_life = 12h 0m 0s
max_renewable_life = 7d 0h 0m 0s
master_key_type = aes256-cts
supported_enctypes = aes256-cts:normal aes128-cts:normal
# If the default location does not suit your setup,
# explicitly configure the following values:
# database_name = /var/krb5kdc/principal
# key_stash_file = /var/krb5kdc/.k5.ATHENA.MIT.EDU
# acl_file = /var/krb5kdc/kadm5.acl
}
[logging]
# By default, the KDC and kadmind will log output using
# syslog. You can instead send log output to files like this:
kdc = FILE:/var/log/krb5kdc.log
admin_server = FILE:/var/log/kadmin.log
default = FILE:/var/log/krb5lib.log
</pre></div>
</div>
<p>Replace <tt class="docutils literal"><span class="pre">ATHENA.MIT.EDU</span></tt> and <tt class="docutils literal"><span class="pre">kerberos.mit.edu</span></tt> with the name of
your Kerberos realm and server respectively.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">You have to have write permission on the target directories
(these directories must exist) used by <strong>database_name</strong>,
<strong>key_stash_file</strong>, and <strong>acl_file</strong>.</p>
</div>
</div>
</div>
<div class="section" id="create-the-kdc-database">
<span id="create-db"></span><h2>Create the KDC database<a class="headerlink" href="#create-the-kdc-database" title="Permalink to this headline">¶</a></h2>
<p>You will use the <a class="reference internal" href="admin_commands/kdb5_util.html#kdb5-util-8"><em>kdb5_util</em></a> command on the master KDC to
create the Kerberos database and the optional <a class="reference internal" href="../basic/stash_file_def.html#stash-definition"><em>stash file</em></a>.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">If you choose not to install a stash file, the KDC will
prompt you for the master key each time it starts up. This
means that the KDC will not be able to start automatically,
such as after a system reboot.</p>
</div>
<p><a class="reference internal" href="admin_commands/kdb5_util.html#kdb5-util-8"><em>kdb5_util</em></a> will prompt you for the master password for the
Kerberos database. This password can be any string. A good password
is one you can remember, but that no one else can guess. Examples of
bad passwords are words that can be found in a dictionary, any common
or popular name, especially a famous person (or cartoon character),
your username in any form (e.g., forward, backward, repeated twice,
etc.), and any of the sample passwords that appear in this manual.
One example of a password which might be good if it did not appear in
this manual is “MITiys4K5!”, which represents the sentence “MIT is
your source for Kerberos 5!” (It’s the first letter of each word,
substituting the numeral “4” for the word “for”, and includes the
punctuation mark at the end.)</p>
<p>The following is an example of how to create a Kerberos database and
stash file on the master KDC, using the <a class="reference internal" href="admin_commands/kdb5_util.html#kdb5-util-8"><em>kdb5_util</em></a> command.
Replace <tt class="docutils literal"><span class="pre">ATHENA.MIT.EDU</span></tt> with the name of your Kerberos realm:</p>
<div class="highlight-python"><div class="highlight"><pre>shell% kdb5_util create -r ATHENA.MIT.EDU -s
Initializing database '/usr/local/var/krb5kdc/principal' for realm 'ATHENA.MIT.EDU',
master key name 'K/M@ATHENA.MIT.EDU'
You will be prompted for the database Master Password.
It is important that you NOT FORGET this password.
Enter KDC database master key: <= Type the master password.
Re-enter KDC database master key to verify: <= Type it again.
shell%
</pre></div>
</div>
<p>This will create five files in <a class="reference internal" href="../mitK5defaults.html#paths"><em>LOCALSTATEDIR</em></a><tt class="docutils literal"><span class="pre">/krb5kdc</span></tt> (or at the locations specified
in <a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><em>kdc.conf</em></a>):</p>
<ul class="simple">
<li>two Kerberos database files, <tt class="docutils literal"><span class="pre">principal</span></tt>, and <tt class="docutils literal"><span class="pre">principal.ok</span></tt></li>
<li>the Kerberos administrative database file, <tt class="docutils literal"><span class="pre">principal.kadm5</span></tt></li>
<li>the administrative database lock file, <tt class="docutils literal"><span class="pre">principal.kadm5.lock</span></tt></li>
<li>the stash file, in this example <tt class="docutils literal"><span class="pre">.k5.ATHENA.MIT.EDU</span></tt>. If you do
not want a stash file, run the above command without the <strong>-s</strong>
option.</li>
</ul>
<p>For more information on administrating Kerberos database see
<a class="reference internal" href="database.html#db-operations"><em>Operations on the Kerberos database</em></a>.</p>
</div>
<div class="section" id="add-administrators-to-the-acl-file">
<span id="admin-acl"></span><h2>Add administrators to the ACL file<a class="headerlink" href="#add-administrators-to-the-acl-file" title="Permalink to this headline">¶</a></h2>
<p>Next, you need create an Access Control List (ACL) file and put the
Kerberos principal of at least one of the administrators into it.
This file is used by the <a class="reference internal" href="admin_commands/kadmind.html#kadmind-8"><em>kadmind</em></a> daemon to control which
principals may view and make privileged modifications to the Kerberos
database files. The ACL filename is determined by the <strong>acl_file</strong>
variable in <a class="reference internal" href="conf_files/kdc_conf.html#kdc-conf-5"><em>kdc.conf</em></a>; the default is <a class="reference internal" href="../mitK5defaults.html#paths"><em>LOCALSTATEDIR</em></a><tt class="docutils literal"><span class="pre">/krb5kdc</span></tt><tt class="docutils literal"><span class="pre">/kadm5.acl</span></tt>.</p>
<p>For more information on Kerberos ACL file see <a class="reference internal" href="conf_files/kadm5_acl.html#kadm5-acl-5"><em>kadm5.acl</em></a>.</p>
</div>
<div class="section" id="add-administrators-to-the-kerberos-database">
<span id="addadmin-kdb"></span><h2>Add administrators to the Kerberos database<a class="headerlink" href="#add-administrators-to-the-kerberos-database" title="Permalink to this headline">¶</a></h2>
<p>Next you need to add administrative principals (i.e., principals who
are allowed to administer Kerberos database) to the Kerberos database.
You <em>must</em> add at least one principal now to allow communication
between the Kerberos administration daemon kadmind and the kadmin
program over the network for further administration. To do this, use
the kadmin.local utility on the master KDC. kadmin.local is designed
to be run on the master KDC host without using Kerberos authentication
to an admin server; instead, it must have read and write access to the
Kerberos database on the local filesystem.</p>
<p>The administrative principals you create should be the ones you added
to the ACL file (see <a class="reference internal" href="#admin-acl"><em>Add administrators to the ACL file</em></a>).</p>
<p>In the following example, the administrative principal <tt class="docutils literal"><span class="pre">admin/admin</span></tt>
is created:</p>
<div class="highlight-python"><div class="highlight"><pre>shell% kadmin.local
kadmin.local: addprinc admin/admin@ATHENA.MIT.EDU
WARNING: no policy specified for "admin/admin@ATHENA.MIT.EDU";
assigning "default".
Enter password for principal admin/admin@ATHENA.MIT.EDU: <= Enter a password.
Re-enter password for principal admin/admin@ATHENA.MIT.EDU: <= Type it again.
Principal "admin/admin@ATHENA.MIT.EDU" created.
kadmin.local:
</pre></div>
</div>
</div>
<div class="section" id="start-the-kerberos-daemons-on-the-master-kdc">
<span id="start-kdc-daemons"></span><h2>Start the Kerberos daemons on the master KDC<a class="headerlink" href="#start-the-kerberos-daemons-on-the-master-kdc" title="Permalink to this headline">¶</a></h2>
<p>At this point, you are ready to start the Kerberos KDC
(<a class="reference internal" href="admin_commands/krb5kdc.html#krb5kdc-8"><em>krb5kdc</em></a>) and administrative daemons on the Master KDC. To
do so, type:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">shell</span><span class="o">%</span> <span class="n">krb5kdc</span>
<span class="n">shell</span><span class="o">%</span> <span class="n">kadmind</span>
</pre></div>
</div>
<p>Each server daemon will fork and run in the background.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Assuming you want these daemons to start up automatically at
boot time, you can add them to the KDC’s <tt class="docutils literal"><span class="pre">/etc/rc</span></tt> or
<tt class="docutils literal"><span class="pre">/etc/inittab</span></tt> file. You need to have a
<a class="reference internal" href="../basic/stash_file_def.html#stash-definition"><em>stash file</em></a> in order to do this.</p>
</div>
<p>You can verify that they started properly by checking for their
startup messages in the logging locations you defined in
<a class="reference internal" href="conf_files/krb5_conf.html#krb5-conf-5"><em>krb5.conf</em></a> (see <a class="reference internal" href="conf_files/kdc_conf.html#logging"><em>[logging]</em></a>). For example:</p>
<div class="highlight-python"><div class="highlight"><pre>shell% tail /var/log/krb5kdc.log
Dec 02 12:35:47 beeblebrox krb5kdc[3187](info): commencing operation
shell% tail /var/log/kadmin.log
Dec 02 12:35:52 beeblebrox kadmind[3189](info): starting
</pre></div>
</div>
<p>Any errors the daemons encounter while starting will also be listed in
the logging output.</p>
<p>As an additional verification, check if <a class="reference internal" href="../user/user_commands/kinit.html#kinit-1"><em>kinit</em></a> succeeds
against the principals that you have created on the previous step
(<a class="reference internal" href="#addadmin-kdb"><em>Add administrators to the Kerberos database</em></a>). Run:</p>
<div class="highlight-python"><div class="highlight"><pre>shell% kinit admin/admin@ATHENA.MIT.EDU
</pre></div>
</div>
</div>
<div class="section" id="install-the-slave-kdcs">
<h2>Install the slave KDCs<a class="headerlink" href="#install-the-slave-kdcs" title="Permalink to this headline">¶</a></h2>
<p>You are now ready to start configuring the slave KDCs.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Assuming you are setting the KDCs up so that you can easily
switch the master KDC with one of the slaves, you should
perform each of these steps on the master KDC as well as the
slave KDCs, unless these instructions specify otherwise.</p>
</div>
<div class="section" id="create-host-keytabs-for-slave-kdcs">
<span id="slave-host-key"></span><h3>Create host keytabs for slave KDCs<a class="headerlink" href="#create-host-keytabs-for-slave-kdcs" title="Permalink to this headline">¶</a></h3>
<p>Each KDC needs a <tt class="docutils literal"><span class="pre">host</span></tt> key in the Kerberos database. These keys
are used for mutual authentication when propagating the database dump
file from the master KDC to the secondary KDC servers.</p>
<p>On the master KDC, connect to administrative interface and create the
host principal for each of the KDCs’ <tt class="docutils literal"><span class="pre">host</span></tt> services. For example,
if the master KDC were called <tt class="docutils literal"><span class="pre">kerberos.mit.edu</span></tt>, and you had a
slave KDC named <tt class="docutils literal"><span class="pre">kerberos-1.mit.edu</span></tt>, you would type the following:</p>
<div class="highlight-python"><div class="highlight"><pre>shell% kadmin
kadmin: addprinc -randkey host/kerberos.mit.edu
NOTICE: no policy specified for "host/kerberos.mit.edu@ATHENA.MIT.EDU"; assigning "default"
Principal "host/kerberos.mit.edu@ATHENA.MIT.EDU" created.
kadmin: addprinc -randkey host/kerberos-1.mit.edu
NOTICE: no policy specified for "host/kerberos-1.mit.edu@ATHENA.MIT.EDU"; assigning "default"
Principal "host/kerberos-1.mit.edu@ATHENA.MIT.EDU" created.
</pre></div>
</div>
<p>It is not strictly necessary to have the master KDC server in the
Kerberos database, but it can be handy if you want to be able to swap
the master KDC with one of the slaves.</p>
<p>Next, extract <tt class="docutils literal"><span class="pre">host</span></tt> random keys for all participating KDCs and
store them in each host’s default keytab file. Ideally, you should
extract each keytab locally on its own KDC. If this is not feasible,
you should use an encrypted session to send them across the network.
To extract a keytab directly on a slave KDC called
<tt class="docutils literal"><span class="pre">kerberos-1.mit.edu</span></tt>, you would execute the following command:</p>
<div class="highlight-python"><div class="highlight"><pre>kadmin: ktadd host/kerberos-1.mit.edu
Entry for principal host/kerberos-1.mit.edu with kvno 2, encryption
type aes256-cts-hmac-sha1-96 added to keytab FILE:/etc/krb5.keytab.
Entry for principal host/kerberos-1.mit.edu with kvno 2, encryption
type aes128-cts-hmac-sha1-96 added to keytab FILE:/etc/krb5.keytab.
Entry for principal host/kerberos-1.mit.edu with kvno 2, encryption
type des3-cbc-sha1 added to keytab FILE:/etc/krb5.keytab.
Entry for principal host/kerberos-1.mit.edu with kvno 2, encryption
type arcfour-hmac added to keytab FILE:/etc/krb5.keytab.
</pre></div>
</div>
<p>If you are instead extracting a keytab for the slave KDC called
<tt class="docutils literal"><span class="pre">kerberos-1.mit.edu</span></tt> on the master KDC, you should use a dedicated
temporary keytab file for that machine’s keytab:</p>
<div class="highlight-python"><div class="highlight"><pre>kadmin: ktadd -k /tmp/kerberos-1.keytab host/kerberos-1.mit.edu
Entry for principal host/kerberos-1.mit.edu with kvno 2, encryption
type aes256-cts-hmac-sha1-96 added to keytab FILE:/etc/krb5.keytab.
Entry for principal host/kerberos-1.mit.edu with kvno 2, encryption
type aes128-cts-hmac-sha1-96 added to keytab FILE:/etc/krb5.keytab.
</pre></div>
</div>
<p>The file <tt class="docutils literal"><span class="pre">/tmp/kerberos-1.keytab</span></tt> can then be installed as
<tt class="docutils literal"><span class="pre">/etc/krb5.keytab</span></tt> on the host <tt class="docutils literal"><span class="pre">kerberos-1.mit.edu</span></tt>.</p>
</div>
<div class="section" id="configure-slave-kdcs">
<h3>Configure slave KDCs<a class="headerlink" href="#configure-slave-kdcs" title="Permalink to this headline">¶</a></h3>
<p>Database propagation copies the contents of the master’s database, but
does not propagate configuration files, stash files, or the kadm5 ACL
file. The following files must be copied by hand to each slave (see
<a class="reference internal" href="../mitK5defaults.html#mitk5defaults"><em>MIT Kerberos defaults</em></a> for the default locations for these files):</p>
<ul class="simple">
<li>krb5.conf</li>
<li>kdc.conf</li>
<li>kadm5.acl</li>
<li>master key stash file</li>
</ul>
<p>Move the copied files into their appropriate directories, exactly as
on the master KDC. kadm5.acl is only needed to allow a slave to swap
with the master KDC.</p>
<p>The database is propagated from the master KDC to the slave KDCs via
the <a class="reference internal" href="admin_commands/kpropd.html#kpropd-8"><em>kpropd</em></a> daemon. You must explicitly specify the
principals which are allowed to provide Kerberos dump updates on the
slave machine with a new database. Create a file named kpropd.acl in
the KDC state directory containing the <tt class="docutils literal"><span class="pre">host</span></tt> principals for each of
the KDCs:</p>
<div class="highlight-python"><div class="highlight"><pre>host/kerberos.mit.edu@ATHENA.MIT.EDU
host/kerberos-1.mit.edu@ATHENA.MIT.EDU
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">If you expect that the master and slave KDCs will be
switched at some point of time, list the host principals
from all participating KDC servers in kpropd.acl files on
all of the KDCs. Otherwise, you only need to list the
master KDC’s host principal in the kpropd.acl files of the
slave KDCs.</p>
</div>
<p>Then, add the following line to <tt class="docutils literal"><span class="pre">/etc/inetd.conf</span></tt> on each KDC
(adjust the path to kpropd):</p>
<div class="highlight-python"><div class="highlight"><pre>krb5_prop stream tcp nowait root /usr/local/sbin/kpropd kpropd
</pre></div>
</div>
<p>You also need to add the following line to <tt class="docutils literal"><span class="pre">/etc/services</span></tt> on each
KDC, if it is not already present (assuming that the default port is
used):</p>
<div class="highlight-python"><div class="highlight"><pre>krb5_prop 754/tcp # Kerberos slave propagation
</pre></div>
</div>
<p>Restart inetd daemon.</p>
<p>Alternatively, start <a class="reference internal" href="admin_commands/kpropd.html#kpropd-8"><em>kpropd</em></a> as a stand-alone daemon. This is
required when incremental propagation is enabled.</p>
<p>Now that the slave KDC is able to accept database propagation, you’ll
need to propagate the database from the master server.</p>
<p>NOTE: Do not start the slave KDC yet; you still do not have a copy of
the master’s database.</p>
</div>
<div class="section" id="propagate-the-database-to-each-slave-kdc">
<span id="kprop-to-slaves"></span><h3>Propagate the database to each slave KDC<a class="headerlink" href="#propagate-the-database-to-each-slave-kdc" title="Permalink to this headline">¶</a></h3>
<p>First, create a dump file of the database on the master KDC, as
follows:</p>
<div class="highlight-python"><div class="highlight"><pre>shell% kdb5_util dump /usr/local/var/krb5kdc/slave_datatrans
</pre></div>
</div>
<p>Then, manually propagate the database to each slave KDC, as in the
following example:</p>
<div class="highlight-python"><div class="highlight"><pre>shell% kprop -f /usr/local/var/krb5kdc/slave_datatrans kerberos-1.mit.edu
Database propagation to kerberos-1.mit.edu: SUCCEEDED
</pre></div>
</div>
<p>You will need a script to dump and propagate the database. The
following is an example of a Bourne shell script that will do this.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Remember that you need to replace <tt class="docutils literal"><span class="pre">/usr/local/var/krb5kdc</span></tt>
with the name of the KDC state directory.</p>
</div>
<div class="highlight-python"><div class="highlight"><pre>#!/bin/sh
kdclist = "kerberos-1.mit.edu kerberos-2.mit.edu"
kdb5_util dump /usr/local/var/krb5kdc/slave_datatrans
for kdc in $kdclist
do
kprop -f /usr/local/var/krb5kdc/slave_datatrans $kdc
done
</pre></div>
</div>
<p>You will need to set up a cron job to run this script at the intervals
you decided on earlier (see <a class="reference internal" href="realm_config.html#db-prop"><em>Database propagation</em></a>).</p>
<p>Now that the slave KDC has a copy of the Kerberos database, you can
start the krb5kdc daemon:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">shell</span><span class="o">%</span> <span class="n">krb5kdc</span>
</pre></div>
</div>
<p>As with the master KDC, you will probably want to add this command to
the KDCs’ <tt class="docutils literal"><span class="pre">/etc/rc</span></tt> or <tt class="docutils literal"><span class="pre">/etc/inittab</span></tt> files, so they will start
the krb5kdc daemon automatically at boot time.</p>
<div class="section" id="propagation-failed">
<h4>Propagation failed?<a class="headerlink" href="#propagation-failed" title="Permalink to this headline">¶</a></h4>
<p>You may encounter the following error messages. For a more detailed
discussion on possible causes and solutions click on the error link
to be redirected to <a class="reference internal" href="troubleshoot.html#troubleshoot"><em>Troubleshooting</em></a> section.</p>
<ol class="arabic simple">
<li><a class="reference internal" href="troubleshoot.html#kprop-no-route"><em>kprop: No route to host while connecting to server</em></a></li>
<li><a class="reference internal" href="troubleshoot.html#kprop-con-refused"><em>kprop: Connection refused while connecting to server</em></a></li>
<li><a class="reference internal" href="troubleshoot.html#kprop-sendauth-exchange"><em>kprop: Server rejected authentication (during sendauth exchange) while authenticating to server</em></a></li>
</ol>
</div>
</div>
</div>
<div class="section" id="add-kerberos-principals-to-the-database">
<h2>Add Kerberos principals to the database<a class="headerlink" href="#add-kerberos-principals-to-the-database" title="Permalink to this headline">¶</a></h2>
<p>Once your KDCs are set up and running, you are ready to use
<a class="reference internal" href="admin_commands/kadmin_local.html#kadmin-1"><em>kadmin</em></a> to load principals for your users, hosts, and other
services into the Kerberos database. This procedure is described
fully in <a class="reference internal" href="database.html#add-mod-del-princs"><em>Adding, modifying and deleting principals</em></a>.</p>
<p>You may occasionally want to use one of your slave KDCs as the master.
This might happen if you are upgrading the master KDC, or if your
master KDC has a disk crash. See the following section for the
instructions.</p>
</div>
<div class="section" id="switching-master-and-slave-kdcs">
<span id="switch-master-slave"></span><h2>Switching master and slave KDCs<a class="headerlink" href="#switching-master-and-slave-kdcs" title="Permalink to this headline">¶</a></h2>
<p>You may occasionally want to use one of your slave KDCs as the master.
This might happen if you are upgrading the master KDC, or if your
master KDC has a disk crash.</p>
<p>Assuming you have configured all of your KDCs to be able to function
as either the master KDC or a slave KDC (as this document recommends),
all you need to do to make the changeover is:</p>
<p>If the master KDC is still running, do the following on the <em>old</em>
master KDC:</p>
<ol class="arabic simple">
<li>Kill the kadmind process.</li>
<li>Disable the cron job that propagates the database.</li>
<li>Run your database propagation script manually, to ensure that the
slaves all have the latest copy of the database (see
<a class="reference internal" href="#kprop-to-slaves"><em>Propagate the database to each slave KDC</em></a>).</li>
</ol>
<p>On the <em>new</em> master KDC:</p>
<ol class="arabic simple">
<li>Start the <a class="reference internal" href="admin_commands/kadmind.html#kadmind-8"><em>kadmind</em></a> daemon (see <a class="reference internal" href="#start-kdc-daemons"><em>Start the Kerberos daemons on the master KDC</em></a>).</li>
<li>Set up the cron job to propagate the database (see
<a class="reference internal" href="#kprop-to-slaves"><em>Propagate the database to each slave KDC</em></a>).</li>
<li>Switch the CNAMEs of the old and new master KDCs. If you can’t do
this, you’ll need to change the <a class="reference internal" href="conf_files/krb5_conf.html#krb5-conf-5"><em>krb5.conf</em></a> file on every
client machine in your Kerberos realm.</li>
</ol>
</div>
<div class="section" id="incremental-database-propagation">
<h2>Incremental database propagation<a class="headerlink" href="#incremental-database-propagation" title="Permalink to this headline">¶</a></h2>
<p>If you expect your Kerberos database to become large, you may wish to
set up incremental propagation to slave KDCs. See <a class="reference internal" href="database.html#incr-db-prop"><em>Incremental database propagation</em></a>
for details.</p>
</div>
</div>
</div>
</div>
</div>
</div>
<div class="sidebar">
<h2>On this page</h2>
<ul>
<li><a class="reference internal" href="#">Installing KDCs</a><ul>
<li><a class="reference internal" href="#install-and-configure-the-master-kdc">Install and configure the master KDC</a></li>
<li><a class="reference internal" href="#edit-kdc-configuration-files">Edit KDC configuration files</a><ul>
<li><a class="reference internal" href="#krb5-conf">krb5.conf</a></li>
<li><a class="reference internal" href="#kdc-conf">kdc.conf</a></li>
</ul>
</li>
<li><a class="reference internal" href="#create-the-kdc-database">Create the KDC database</a></li>
<li><a class="reference internal" href="#add-administrators-to-the-acl-file">Add administrators to the ACL file</a></li>
<li><a class="reference internal" href="#add-administrators-to-the-kerberos-database">Add administrators to the Kerberos database</a></li>
<li><a class="reference internal" href="#start-the-kerberos-daemons-on-the-master-kdc">Start the Kerberos daemons on the master KDC</a></li>
<li><a class="reference internal" href="#install-the-slave-kdcs">Install the slave KDCs</a><ul>
<li><a class="reference internal" href="#create-host-keytabs-for-slave-kdcs">Create host keytabs for slave KDCs</a></li>
<li><a class="reference internal" href="#configure-slave-kdcs">Configure slave KDCs</a></li>
<li><a class="reference internal" href="#propagate-the-database-to-each-slave-kdc">Propagate the database to each slave KDC</a><ul>
<li><a class="reference internal" href="#propagation-failed">Propagation failed?</a></li>
</ul>
</li>
</ul>
</li>
<li><a class="reference internal" href="#add-kerberos-principals-to-the-database">Add Kerberos principals to the database</a></li>
<li><a class="reference internal" href="#switching-master-and-slave-kdcs">Switching master and slave KDCs</a></li>
<li><a class="reference internal" href="#incremental-database-propagation">Incremental database propagation</a></li>
</ul>
</li>
</ul>
<br/>
<h2>Table of contents</h2>
<ul class="current">
<li class="toctree-l1"><a class="reference internal" href="../user/index.html">For users</a></li>
<li class="toctree-l1 current"><a class="reference internal" href="index.html">For administrators</a><ul class="current">
<li class="toctree-l2 current"><a class="reference internal" href="install.html">Installation guide</a><ul class="current">
<li class="toctree-l3 current"><a class="current reference internal" href="">Installing KDCs</a></li>
<li class="toctree-l3"><a class="reference internal" href="install_clients.html">Installing and configuring UNIX client machines</a></li>
<li class="toctree-l3"><a class="reference internal" href="install_appl_srv.html">UNIX Application Servers</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="conf_files/index.html">Configuration Files</a></li>
<li class="toctree-l2"><a class="reference internal" href="realm_config.html">Realm configuration decisions</a></li>
<li class="toctree-l2"><a class="reference internal" href="database.html">Database administration</a></li>
<li class="toctree-l2"><a class="reference internal" href="lockout.html">Account lockout</a></li>
<li class="toctree-l2"><a class="reference internal" href="conf_ldap.html">Configuring Kerberos with OpenLDAP back-end</a></li>
<li class="toctree-l2"><a class="reference internal" href="appl_servers.html">Application servers</a></li>
<li class="toctree-l2"><a class="reference internal" href="host_config.html">Host configuration</a></li>
<li class="toctree-l2"><a class="reference internal" href="backup_host.html">Backups of secure hosts</a></li>
<li class="toctree-l2"><a class="reference internal" href="pkinit.html">PKINIT configuration</a></li>
<li class="toctree-l2"><a class="reference internal" href="otp.html">OTP Preauthentication</a></li>
<li class="toctree-l2"><a class="reference internal" href="princ_dns.html">Principal names and DNS</a></li>
<li class="toctree-l2"><a class="reference internal" href="enctypes.html">Encryption types</a></li>
<li class="toctree-l2"><a class="reference internal" href="https.html">HTTPS proxy configuration</a></li>
<li class="toctree-l2"><a class="reference internal" href="auth_indicator.html">Authentication indicators</a></li>
<li class="toctree-l2"><a class="reference internal" href="admin_commands/index.html">Administration programs</a></li>
<li class="toctree-l2"><a class="reference internal" href="../mitK5defaults.html">MIT Kerberos defaults</a></li>
<li class="toctree-l2"><a class="reference internal" href="env_variables.html">Environment variables</a></li>
<li class="toctree-l2"><a class="reference internal" href="troubleshoot.html">Troubleshooting</a></li>
<li class="toctree-l2"><a class="reference internal" href="advanced/index.html">Advanced topics</a></li>
<li class="toctree-l2"><a class="reference internal" href="various_envs.html">Various links</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="../appdev/index.html">For application developers</a></li>
<li class="toctree-l1"><a class="reference internal" href="../plugindev/index.html">For plugin module developers</a></li>
<li class="toctree-l1"><a class="reference internal" href="../build/index.html">Building Kerberos V5</a></li>
<li class="toctree-l1"><a class="reference internal" href="../basic/index.html">Kerberos V5 concepts</a></li>
<li class="toctree-l1"><a class="reference internal" href="../formats/index.html">Protocols and file formats</a></li>
<li class="toctree-l1"><a class="reference internal" href="../mitK5features.html">MIT Kerberos features</a></li>
<li class="toctree-l1"><a class="reference internal" href="../build_this.html">How to build this documentation from the source</a></li>
<li class="toctree-l1"><a class="reference internal" href="../about.html">Contributing to the MIT Kerberos Documentation</a></li>
<li class="toctree-l1"><a class="reference internal" href="../resources.html">Resources</a></li>
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