After Ubuntu has been installed, some of it's configuration files need to be modified. To simplify the setup, the default configuration of the UCS master domain controller should be copied to the Ubuntu system, for example:

# Become root
sudo bash

# Set the IP address of the UCS DC Master, 192.168.0.3 in this example
export MASTER_IP=192.168.0.3

mkdir /etc/univention
ssh root@${MASTER_IP} ucr shell |
 grep -v ^hostname= >/etc/univention/ucr_master
echo "master_ip=${MASTER_IP}" >>/etc/univention/ucr_master
chmod 660 /etc/univention/ucr_master
. /etc/univention/ucr_master

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

# Exit sudo bash
exit

In the default configuration of UCS only authenticated users can search in the LDAP directory. As such, the Ubuntu client needs an account in the UCS domain to gain read access to the LDAP directory:

# Become root
sudo bash

# 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="$(tr -dc A-Za-z0-9_ </dev/urandom | head -c20)"
ssh root@${ldap_master} udm computers/ubuntu create \
    --position "cn=computers,${ldap_base}" \
    --set name=$(hostname) --set password="${password}" \
    --set operatingSystem="$(lsb_release -is)" \
    --set operatingSystemVersion="$(lsb_release -rs)"
printf '%s' "$password" >/etc/ldap.secret
chmod 0400 /etc/ldap.secret

# 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__

# Exit sudo bash
exit

SSSD provides a set of daemons to manage access to remote directories and authentication mechanisms.

# Become root
sudo bash

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

# Install SSSD based configuration
DEBIAN_FRONTEND=noninteractive apt-get -y install sssd libnss-sss libpam-sss libsss-sudo

# Create sssd.conf
cat >/etc/sssd/sssd.conf <<__EOF__
[sssd]
config_file_version = 2
reconnection_retries = 3
sbus_timeout = 30
services = nss, pam, sudo
domains = $kerberos_realm

[nss]
reconnection_retries = 3

[pam]
reconnection_retries = 3

[domain/$kerberos_realm]
auth_provider = krb5
krb5_kdcip = ${master_ip}
krb5_realm = ${kerberos_realm}
krb5_server = ${ldap_master}
krb5_kpasswd = ${ldap_master}
id_provider = ldap
ldap_uri = ldap://${ldap_master}:7389
ldap_search_base = ${ldap_base}
ldap_tls_reqcert = never
ldap_tls_cacert = /etc/univention/ssl/ucsCA/CAcert.pem
cache_credentials = true
enumerate = true
ldap_default_bind_dn = cn=$(hostname),cn=computers,${ldap_base}
ldap_default_authtok_type = password
ldap_default_authtok = $(cat /etc/ldap.secret)
__EOF__
chmod 600 /etc/sssd/sssd.conf

# Install auth-client-config
DEBIAN_FRONTEND=noninteractive apt-get -y install auth-client-config

# Create an auth config profile for sssd
cat >/etc/auth-client-config/profile.d/sss <<__EOF__
[sss]
nss_passwd=   passwd:   compat sss
nss_group=    group:    compat sss
nss_shadow=   shadow:   compat
nss_netgroup= netgroup: nis

pam_auth=
        auth [success=3 default=ignore] pam_unix.so nullok_secure try_first_pass
        auth requisite pam_succeed_if.so uid >= 500 quiet
        auth [success=1 default=ignore] pam_sss.so use_first_pass
        auth requisite pam_deny.so
        auth required pam_permit.so

pam_account=
        account required pam_unix.so
        account sufficient pam_localuser.so
        account sufficient pam_succeed_if.so uid < 500 quiet
        account [default=bad success=ok user_unknown=ignore] pam_sss.so
        account required pam_permit.so

pam_password=
        password sufficient pam_unix.so obscure sha512
        password sufficient pam_sss.so use_authtok
        password required pam_deny.so

pam_session=
        session required pam_mkhomedir.so skel=/etc/skel/ umask=0077
        session optional pam_keyinit.so revoke
        session required pam_limits.so
        session [success=1 default=ignore] pam_sss.so
        session required pam_unix.so
__EOF__
auth-client-config -a -p sss

# Restart sssd
restart sssd

# Exit sudo bash
exit

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

The home directory of a user should be created automatically during login:

# Become root
sudo bash

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

# Exit sudo bash
exit

During login users should also be added to some system groups:

# Become root
sudo bash

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

# Exit sudo bash
exit

By default the Ubuntu login manager only displays a list of local users during login. After adding the following lines an arbitrary user name can be used:

# Become root
sudo bash

# Add a field for a user name, disable user selection at the login screen
mkdir /etc/lightdm/lightdm.conf.d
cat >>/etc/lightdm/lightdm.conf.d/99-show-manual-userlogin.conf <<__EOF__
[SeatDefaults]
greeter-show-manual-login=true
greeter-hide-users=true
__EOF__

# Exit sudo bash
exit

Kubuntu 14.04 uses AccountService, a D-Bus interface for user account management, which ignores the /etc/lightdm.conf file. Since there is no configuration file for AccountService the login theme needs to be changed to classic under System Settings -> Login Screen (LightDM).

With these settings the login for domain members should be possible after a restart of LightDM or a reboot.

Every UCS domain provides a Kerberos domain. Since Kerberos relies on DNS, the Ubuntu client should use a UCS domain controller as its DNS server. The following steps provide an example configuration for Kerberos:

# Become root
sudo bash

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

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

# 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 = $master_ip $ldap_master
   admin_server = $master_ip $ldap_master
}
__EOF__

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

# Synchronize the time with the UCS system
ntpdate -bu $ldap_master

# Test Kerberos: kinit will ask you for a ticket and the SSH login to the master should work with ticket authentication:
kinit Administrator
ssh Administrator@$ldap_master ls /etc/univention

# Destroy the kerberos ticket
kdestroy

# Exit sudo bash
exit

It is currently not possible to change the user password at the LightDM login manager. Instead, the password can be changed via the kpasswd command after login or via the UMC module Change password.

A Computer: Linux object can be created in the UMC computer management. This allows the integration of the Unix system in the DNS/DHCP and network administration of the Univention Management Console

If the Nagios support is enabled under [Options], remote Nagios checks can also be applied against the system.

The Unix system should use a name server from the UCS domain: All UCS domain controllers (i.e., master domain controller, backup domain controller and slave domain controller) operate a DNS server. One or more of these UCS system should be entered in the /etc/resolv.conf, e.g.:

domain  example.com
nameserver  10.200.3.108
nameserver  10.200.3.99

All UCS domain controllers (i.e., master domain controller, backup domain controller and slave domain controller) operate a NTP server.

The configuration differs depending on the NTP software used, but is set under /etc/ntp.conf on most Linux systems, e.g.:

server master.example.com
server backup.example.com

The Name Service Switch (NSS) is an interface for configuring the data sources for users, groups and computers. NSS is present on all Linux versions and most Unix systems.

If the Unix system used provides support for an NSS module for LDAP access - as is the case in most Linux distributions - user and group information can be read out of the UCS LDAP directory.

The configuration files of the NSS LDAP module differ depending on the Linux/Unix version.

As a general rule, the following settings must be set there:

If the NSS LDAP service has been set up correctly, the following two commands should output all users and groups:

getent passwd
getent group

UCS employs the Kerberos implementation Heimdal. For this reason, Heimdal should also be used to access the Kerberos realm on the Unix system. Only the Heimdal client libraries need to be installed on the Unix system.

Kerberos requires correct time synchronisation, see Section 2.2.

The configuration is performed in the /etc/krb5.conf file on most systems. Here is an example configuration:

[libdefaults]
    default_realm = KERBEROSREALM
    default_tkt_enctypes = arcfour-hmac-md5 des-cbc-md5 des3-hmac-sha1 \
       des-cbc-crc des-cbc-md4 des3-cbc-sha1 aes128-cts-hmac-sha1-96   \
       aes256-cts-hmac-sha1-96
    permitted_enctypes = des3-hmac-sha1 des-cbc-crc des-cbc-md4 \
       des-cbc-md5 des3-cbc-sha1 arcfour-hmac-md5               \
       aes128-cts-hmac-sha1-96 aes256-cts-hmac-sha1-96
    allow_weak_crypto=true
    kdc_timesync = 1
    ccache_type = 4
    forwardable = true
    proxiable = true
    kdc_timesync = 1

[realms]
KERBEROSREAKM = {
   kdc = MASTERIP MASTERFQDN
   admin_server = MASTERIP MASTERFQDN
   kpasswd_server = MASTERIP MASTERFQDN
}

The Heimdal PAM module then needs to be installed. In general, the installation of the module should adapt the PAM configuration automatically.

Then Kerberos authentication during login should work via PAM and password changes should be possible via kpasswd.

To allow SSH logins via Kerberos, the options GSSAPIAuthentication and GSSAPIKeyExchange should be set to yes in the configuration file of the SSH daemon (typically /etc/ssh/sshd_config).

UCS uses the Common Unix Printing System (CUPS) to implement print services. The Unix system can use the UCS print servers by installing the CUPS client programs. In addition the CUPS server needs to be configured for the clients, typically in the configuration file /etc/cups/client.conf, e.g.:

ServerName printserver.example.com

Every UCS domain has its own SSL certificate authority. The SSL certificates are created automatically for all UCS systems during the installation (master domain controller) or during the domain join (all other system roles).

The command univention-certificate can be used to manage these certificates, e.g., if it proves necessary to create a certificate for the integration of an external system.

univention-certificate list

univention-certificate dump -name fullyqualifiedhostname

univention-certificate check -name fullyqualifiedhostname

univention-certificate revoke -name fullyqualifiedhostname

univention-certificate new -name fullyqualifiedhostname

A certificate signing request (CSR) is a request submitted to a certificate authority (CA) to create a digital signature. A CSR typically occurs in the form of a file. This section describes how a CSR is signed by the UCS CA.

CERTIFICATE is the file name of the certificate to be created.

REQUEST is the file with the CSR in either PEM or DER format. A file in PEM format is a text file containing a base64 encoded block enclosed between BEGIN CERTIFICATE and END CERTIFICATE. A request in binary DER format must be first converted to the PEM format with the following command:

openssl req \
  -inform  der -in  request.der \
  -outform pem -out req.pem

The following command then processes the CSR and creates the certificate:

openssl ca -batch -config /etc/univention/ssl/openssl.cnf \
  -in REQUEST -out CERTIFICATE \
  -passin file:/etc/univention/ssl/password

This chapter describes the read-only integration of an external OpenLDAP server via a syncrepl proxy. This allows the external system to access the LDAP data of the UCS domain without being a member of the domain itself. This guide principally applies to any Unix system with OpenLDAP. The guide has been tested with Debian 7 Wheezy. Syncrepl is part of OpenLDAP starting with version 2.2.

The external OpenLDAP server is described as extldap.univention.test below and synchronises with the master domain controller, which uses the LDAP base dc=univention,dc=test.

The following steps must be run on the OpenLDAP system and the UCS system as the root user:

For extldap.univention.test, a Linux computer object must be created in the Univention Management Console computer management and a DNS forward and reverse zone assigned to the computer.

Now a syncrepl proxy needs to be set up on the master domain controller. The required configuration files are downloaded from http://apt.univention.de/download/syncrepl/ucs4-syncrepl-proxy-setup.tar.bz2 as a Tar archive.

The downloaded archive must firstly be extracted on the master domain controller:

tar -xvf ucs4-syncrepl-proxy-setup.tar.bz2

The UCS_dc_master subdirectory contains two Univention Configuration Registry subfile templates for the LDAP server configuration file (/etc/ldap/slapd.conf). Subfiles are a mechanism in Univention Configuration Registry which can be used to generate a configuration file from several individual templates. More detailed information can be found in the UCS manual. The two subfiles are now copied into the template directory:

mv UCS_dc_master/8*.conf /etc/univention/templates/files/etc/ldap/slapd.conf.d/
mv UCS_dc_master/syncrepl-proxy.conf /etc/univention/templates/files/etc/ldap/

The info file now needs to be copied. It registers the subfile templates and the Univention Configuration Registry variables used:

mv UCS_dc_master/syncrepl-proxy.info /etc/univention/templates/info/

Then the slapd.conf is regenerated from the template:

ucr commit /etc/ldap/slapd.conf
ucr commit /etc/ldap/syncrepl-proxy.conf

Now an initial copy of the UCS data is created and transferred to the external system. In addition, an initial configuration file for the OpenLDAP service is copied onto the external system (slapd.conf).

slapcat > data.ldif
cat remote_system/template-slapd.conf | ucr filter > remote_system/slapd.conf
scp remote_system/slapd.conf data.ldif extldap.univention.test:
rm data.ldif

The LDAP schema data and the SSL certificates from the UCS master are now passed to the external LDAP server:

rsync -aR /usr/share/univention-ldap/schema extldap.univention.test:/
rsync -aR /var/lib/univention-ldap/local-schema extldap.univention.test:/
rsync -aR /etc/univention/ssl/extldap.univention.test extldap.univention.test:/
rsync -aR /etc/univention/ssl/ucsCA/CAcert.pem extldap.univention.test:/

The configuration of the external LDAP server is now adapted. It must be noted that only a minimal slapd.conf is installed here, which should be expanded with local adaptations as necessary:

/etc/init.d/slapd stop
cp /etc/ldap/slapd.conf /root/backup-slapd.conf
cp /root/slapd.conf /etc/ldap

A number of settings now need to be adapted in the provided /etc/ldap/slapd.conf template:

The initial copy of the UCS directory data is now imported and the LDAP server restarted. The file permissions of the /var/lib/ldap/ directory and the /etc/ldap/slapd.conf file differ depending on the Linux/Unix version:

mkdir /root/ldap_backup_dir
mv /var/lib/ldap/*.* /root/ldap_backup_dir
slapadd -f /etc/ldap/slapd.conf -l /root/data.ldif
chown openldap.openldap /var/lib/ldap/*.*
chgrp openldap /etc/ldap/slapd.conf
chgrp -R openldap /etc/univention/ssl
/etc/init.d/slapd start

The configuration of the external LDAP server is now complete. The following command (performed on the master domain controller) can be used to check whether the external LDAP server can be reached via the LDAPS protocol:

ldapsearch -x -H ldaps://extldap.univention.test -b cn=Subschema -s base

Whenever schema files are added on the UCS Master, the following steps have to be repeated. First an updated slapd.conf needs to be generated for the remote LDAP server which includes all UCS schema files. Then all required files need to be copied to the remote LDAP server:

cat remote_system/template-slapd.conf | ucr filter > remote_system/slapd.conf
scp remote_system/slapd.conf extldap.univention.test:
rsync -aR /usr/share/univention-ldap/schema extldap.univention.test:/
rsync -aR /var/lib/univention-ldap/local-schema extldap.univention.test:/

And after that the following steps need to be repeated on the external LDAP server:

/etc/init.d/slapd stop
cp /etc/ldap/slapd.conf /root/backup-slapd.conf
cp /root/slapd.conf /etc/ldap
chgrp openldap /etc/ldap/slapd.conf
/etc/init.d/slapd start

If the external system is a Debian system, the 'SLAPD_SERVICES' variable may need to be adapted in /etc/default/slapd. In addition, the 'SLAPD_CONF' variable can be used to specify the /etc/ldap/slapd.conf file as the configuration file for the slapd, if this is not the standard for the OpenLDAP version used.

If the LDAP connection works, the configuration of the syncrepl proxy can be activated on the master domain controller. This is done by saving the 'REMOTE_UPDATE_PASSWORD' password configured above in the /etc/replica-001.secret file and entering the address of the external LDAP server in the form of a LDAP-URI in the Univention Configuration Registry variable ldap/replica/target/uri:

echo -n 'REMOTE_UPDATE_PASSWORD' >  /etc/replica-001.secret
chmod 600 /etc/replica-001.secret
univention-config-registry set ldap/replica/target/uri='ldaps://extldap.univention.test/'
ucr commit /etc/ldap/syncrepl-proxy.conf
/etc/init.d/slapd restart

If several systems are connected, the corresponding LDAP-URIs can be entered in the variable separated with commas and additional replica password files created. The number in the name of the password files is incremented by one for each additional system.

The replication originates from the master domain controller and is performed via LDAPS to the host name of the external LDAP server system. This requires working name resolution (typically via DNS). The host name must be specified as a fully qualified domain name to allow checking of the SSL certificate.

To allow convenient LDAP search via ldapsearch -x expression on the external LDAP server the file /etc/ldap/ldap.conf may be configured like this:

TLS_CACERT /etc/univention/ssl/ucsCA/CAcert.pem
HOST FQDN
BASE LDAPBASE

The replication via syncrepl can be tested by changing the description of an existing user for example. When an LDAP search is performed on the external server, the changed description should then be displayed.