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+ <title>Petter Reinholdtsen: Caching password, user and group on a roaming Debian laptop</title>
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+ <div class="title">
+ <h1>
+ <a href="http://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
+
+ </h1>
+
+ </div>
+
+
+ <div class="entry">
+ <div class="title">Caching password, user and group on a roaming Debian laptop</div>
+ <div class="date">2010-05-30 13:00</div>
+ <div class="body">
+<p>For a laptop, centralized user directories and password checking is
+a bit troubling. Laptops are typically used also when not connected
+to the network, and it is vital for a user to be able to log in or
+unlock the screen saver lock also when the central servers are
+unavailable. This is possible by caching passwords and directory
+information locally, and the packages to do so are available in
+Debian. Here follow two recipes to set this up in Debian/Squeeze. It
+is also possible to set up in Debian/Lenny, but require more manual
+setup there because pam-auth-update is missing in Lenny.</p>
+
+<p>If you want to help out with implementing this for Debian Edu,
+please contact us on debian-edu@lists.debian.org.</p>
+
+<h2>LDAP/Kerberos + nscd + libpam-ccreds + libpam-mklocaluser/pam_mkhomedir</h2>
+
+This is the traditional method with a twist. The password caching is
+provided by libpam-ccreds (version 10-4 or later, currently only in
+experimental), and the directory caching is done by nscd. The
+directory lookup and password checking is done using LDAP. If one
+want to use Kerberos for password checking the libpam-ldapd package
+can be replaced with for example libpam-krb5. If one is happy having
+a local home directory with the path listed in LDAP, one can use
+pam_mkhomedir to make this happen. A setup for pam-auth-update will
+have to be written until a fix for
+<a href="http://bugs.debian.org/568577">bug #568577</a> is in the
+
+archive. Because I believe it is a bad idea to have local home
+directories using misleading paths like /site/server/partition/, I
+prefer to create a local user with the home directory in /home/
+instead. This is done using the libpam-mklocaluser package entering
+Squeeze in the next few days.</p>
+
+<p>These packages need to be installed and configured</p>
+
+<blockquote><pre>
+libnss-ldapd libpam-ldapd nscd libpam-ccreds libpam-mklocaluser
+</pre></blockquote>
+
+Because nscd do not have a default configuration fit for offline
+caching until <a href="http://bugs.debian.org/485282">bug #485282</a>
+is fixed, this configuration should be used instead of the one
+currently in /etc/nscd.conf. The changes are in the fields
+reload-count and positive-time-to-live, and is based on the
+instructions I found in the
+<a href="http://www.flyn.org/laptopldap/">LDAP for Mobile Laptops</a>
+instructions by Flyn Computing.
+
+<blockquote><pre>
+ debug-level 0
+ reload-count unlimited
+ paranoia no
+
+ enable-cache passwd yes
+ positive-time-to-live passwd 2592000
+ negative-time-to-live passwd 20
+ suggested-size passwd 211
+ check-files passwd yes
+ persistent passwd yes
+ shared passwd yes
+ max-db-size passwd 33554432
+ auto-propagate passwd yes
+
+ enable-cache group yes
+ positive-time-to-live group 2592000
+ negative-time-to-live group 20
+ suggested-size group 211
+ check-files group yes
+ persistent group yes
+ shared group yes
+ max-db-size group 33554432
+ auto-propagate group yes
+
+ enable-cache hosts no
+ positive-time-to-live hosts 2592000
+ negative-time-to-live hosts 20
+ suggested-size hosts 211
+ check-files hosts yes
+ persistent hosts yes
+ shared hosts yes
+ max-db-size hosts 33554432
+
+ enable-cache services yes
+ positive-time-to-live services 2592000
+ negative-time-to-live services 20
+ suggested-size services 211
+ check-files services yes
+ persistent services yes
+ shared services yes
+ max-db-size services 33554432
+</pre></blockquote>
+
+<p>While we wait for the mechanism to update /etc/nsswitch.conf
+automatically provided in <a href="http://bugs.debian.org/496915">bug
+#496915</a>, it need to be replaced manually to ensure LDAP is used as
+the directory. /etc/nsswitch.conf should look like this:</p>
+
+<blockquote><pre>
+passwd: files ldap
+group: files ldap
+shadow: files ldap
+hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
+networks: files
+protocols: files
+services: files
+ethers: files
+rpc: files
+netgroup: files ldap
+</pre></blockquote>
+
+<h2>LDAP/Kerberos + sssd + libpam-mklocaluser/pam_mkhomedir</h2>
+
+<p>These packages need to be installed and configured</p>
+
+<blockquote><pre>
+libpam-sss libnss-sss libpam-mklocaluser
+</pre></blockquote>
+
+/etc/sssd/sssd.conf
+
+<blockquote><pre>
+[sssd]
+config_file_version = 2
+reconnection_retries = 3
+sbus_timeout = 30
+services = nss, pam
+domains = UIO.NO
+
+[nss]
+filter_groups = root
+filter_users = root
+reconnection_retries = 3
+
+[pam]
+reconnection_retries = 3
+
+[domain/UIO.NO]
+; Using enumerate = true leads to high load and slow response
+enumerate = false
+cache_credentials = true
+
+id_provider = ldap
+auth_provider = ldap
+chpass_provider = ldap
+
+ldap_uri = ldap://ldap.uio.no
+ldap_search_base = cn=system,dc=uio,dc=no
+ldap_tls_reqcert = never
+ldap_tls_cacert = /etc/ssl/certs/ca-certificates.crt
+
+# min_id also filter both uid and gid entries, and usit=300, so we
+# need to lower the default from 1000.
+min_id = 200
+</pre></blockquote>
+
+<blockquote><pre>
+</pre></blockquote>
+</div>
+
+ <div class="tags">Tags: <a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="http://people.skolelinux.org/pere/blog/tags/nuug">nuug</a>.</div>
+
+ </div>
+
+
+
+
+
+
+<div id="sidebar">
+
+<h2>Archive</h2>
+<ul>
+
+<li>2010
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+<li><a href="http://people.skolelinux.org/pere/blog/archive/2010/01/">January (2)</a></li>
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+
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+
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+
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+
+
+
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