Ubuntu – How to configure Ubuntu as an LDAP client


How to configure Ubuntu 12.04 as LDAP client with PAM modules?

Best Answer

The contents of this post are based on this guide. It should work fine in 12.04.

  1. Issue the following command:

    sudo apt-get install ldap-utils libpam-ldap libnss-ldap nslcd

    Note: During the installation of the above packages a dialog will pop up and ask about some LDAP configuration. Be sure to enter the correct values for your LDAP configuration.

  2. Edit /etc/nsswitch.conf (via sudo). Append "ldap" to these lines:

    #Original file looks like this 
    passwd: compat 
    group : compat  
    shadow: compat 
    #After appending "ldap" lines look like these
    passwd: compat ldap
    group : compat ldap  
    shadow: compat ldap 
  3. Comment out the line rootbinddn, I'm not sure why we need to do that.

  4. Edit /etc/pam.d/login (via sudo) and paste:

    session required pam_mkhomedir.so skel=/etc/skel umask=0022 
  5. Edit /etc/pam.d/lightdm (via sudo) and paste:

    session required pam_mkhomedir.so skel=/etc/skel umask=0022 
  6. Issue this command:

    sudo update-rc.d nslcd enable

You should be able to log in as an LDAP user after a reboot. If you don't reboot the machine, you must restart nscd with:

/etc/init.d/nscd restart

Likely problems and solutions:

  • Logging in as an LDAP user takes a very long time (minutes): It's very likely that nss-lap is having problems finding the user's group. Make sure that the user is in a group recognized locally, or that the user is in a group defined in LDAP. Make sure that, if the group is defined in LDAP, that it's a real POSIX group.
  • Always check the /var/log/auth.log log file. If you see "unable to contact ldap server", check whether the LDAP server is reachable and the port is open.
  • Try to ping the LDAP server by name
  • Try to check whether the LDAP port is open:
    • LDAP can listen on different ports, but can usually be found on 389 and 636
    • You can check that a port is open by using telnet:
    • telnet 389 or telnet 636
    • If you see any characters on the console then the port is open and the LDAP server should be running.
    • If you see nothing or get an error message, either the LDAP server is not running or something (such as a firewall) is preventing the connection.