Ubuntu

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Revision as of 07:24, 11 June 2012 by Gulden (talk | contribs) (Minor wording updates.)
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Produktlogo UCS Version 3.0

This guide describes the inclusion of Ubuntu into an UCS 3 domain. This configuration has been tested with Ubuntu 12.04 LTS and Kubuntu 12.04 LTS.

LDAP and SSL configuration

After Ubuntu has been installed, the default basis configuration must be done. For an easy use, the default configuration of the UCS Master should be copied to the Ubuntu system, for example:

export MASTER_IP=10.201.1.1

mkdir /etc/univention
ssh ${MASTER_IP} ucr shell | grep -v ^hostname= >/etc/univention/ucr_master
. /etc/univention/ucr_master

echo "${MASTER_IP} ${ldap_master}" >>/etc/hosts

The anonymous LDAP search is disabled by default in UCS 3. The Ubuntu client needs an account in the UCS 3 domain to get read access to the LDAP directory.

# Set some environment variables
. /etc/univention/ucr_master

# Download the SSL certificate
mkdir -p /etc/univention/ssl/ucsCA/
wget -O /etc/univention/ssl/ucsCA/CAcert.pem http://${ldap_master}/ucs-root-ca.crt

# Create an account and save the password
password="$(< /dev/urandom tr -dc A-Za-z0-9_ | head -c8)"
ssh root@${ldap_master} udm computers/managedclient create --position cn=computers,${ldap_base} \
                        --set name=$(hostname) --set password="${password}"
echo "${password}" > /etc/ldap.secret

# Install LDAP client tools
DEBIAN_FRONTEND=noninteractive apt-get install libnss-ldap ldap-utils nscd

# Create ldap.conf
cat >/etc/ldap/ldap.conf <<__EOF__
TLS_CACERT /etc/univention/ssl/ucsCA/CAcert.pem
URI ldap://$ldap_master:7389
BASE $ldap_base
__EOF__

cat >/etc/ldap.conf <<__EOF__
uri ldap://$ldap_master:7389
rootbinddn cn=$(hostname),cn=computers,${ldap_base}

base ${ldap_base}
ldap_version 3
scope sub
ssl start_tls
tls_checkpeer no
nss_initgroups_ignoreusers root
__EOF__

# Activate ldap in nsswitch
auth-client-config -t nss -p lac_ldap

The commands getent passwd and getent group should now also display all users and groups of the UCS 3 domain.

Login

To allow the users the login the home directory should be created by the login.

cat >/usr/share/pam-configs/ucs_mkhomedir <<__EOF__
Name: activate mkhomedir
Default: yes
Priority: 900
Session-Type: Additional
Session:
        required                        pam_mkhomedir.so umask=0022 skel=/etc/skel
__EOF__

DEBIAN_FRONTEND=noninteractive pam-auth-update

The users should be added to some groups during the login, for example:

echo '*;*;*;Al0000-2400;audio,cdrom,dialout,floppy,plugdev,adm' >>/etc/security/group.conf

cat >>/usr/share/pam-configs/local_groups <<__EOF__
Name: activate /etc/security/group.conf
Default: yes
Priority: 900
Auth-Type: Primary
Auth:
        required                        pam_group.so use_first_pass
__EOF__

DEBIAN_FRONTEND=noninteractive pam-auth-update

By default Ubuntu (12.04 LTS) shows only local users at the login screen. After adding the following line a user name can be added:

# Add a field for a user name
echo "greeter-show-manual-login=true" >>/etc/lightdm/lightdm.conf

# Optional: Disable the user selection at the login screen
echo "greeter-hide-users=true" >>/etc/lightdm/lightdm.conf

With these settings the login for domain members should be possible.

Kerberos integration

An UCS 3 domain provides a kerberos domain. The Ubuntu client should use the UCS 3 DNS server, because Kerberos relies heavily on DNS. The following steps show an example configuration

# Set some environment variables
. /etc/univention/ucr_master

# Install required packages
DEBIAN_FRONTEND=noninteractive apt-get install heimdal-clients libpam-heimdal

# Default krb5.conf
cat >/etc/krb5.conf <<__EOF__
[libdefaults]
    default_realm = $kerberos_realm
    kdc_timesync = 1
    ccache_type = 4
    forwardable = true
    proxiable = true

[realms]
$kerberos_realm = {
   kdc = $ldap_master
   admin_server = $ldap_master
}
__EOF__

# Stop and disable the avahi daemon
service avahi-daemon stop
sed -i 's|start on (|start on (never and |' /etc/init/avahi-daemon.conf

# Synchronize the time with the UCS system
ntpdate $ldap_master

# Test Kerberos
kinit Administrator

# This login shouldn't ask for a password
ssh Administrator@$ldap_master ls /etc/univention

# Destroy the kerberos ticket
kdestroy

Authentication caching

Cached credentials are helpful, if no UCS domain controller can be reached. It can be activated by executing the following steps:

# Install packages
DEBIAN_FRONTEND=noninteractive apt-get install nss-updatedb libnss-db libpam-ccreds 

# Dump the LDAP data
nss_updatedb ldap

# Call it every day
cat >/etc/cron.daily/upd-local-nss-db <<__EOF__
#!/bin/sh
`which nss_updatedb` ldap
__EOF__
chmod +x /etc/cron.daily/upd-local-nss-db

# Added NOTFOUND case for ldap in nsswitch.conf
sed -i 's|^passwd: .*|passwd: files ldap [NOTFOUND=return] db|; \
        s|^group: .*|group: files ldap [NOTFOUND=return] db|' /etc/nsswitch.conf

# Skip pam_ldap if user_unknown or authinfo_unavail as well
sed -i 's/^\(account.*\[success=\)\(.\)\(.*pam_ldap.so\)/\1\2 user_unknown=\2 authinfo_unavail=\2 \3/' \
       /etc/pam.d/common-account

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