How to check the LDAP connection from a client to server. I'm working on the LDAP authentication and this client desktop needs to authenticate via a LDAP server. I can SSH to the LDAP server using LDAP user but When in desktop login prompt, I can't login. It says Authentication failure.

Client machine has Cent OS 6.3 and LDAP server has Cent OS 5.5

LDAP software is Openldap.

LDAP servers logs doesn't even show any messages.

So, how to test whether the client can successfully connect to LDAP or not.

  • 3
    As a minor note to this old post, you can do a search (ie ldapsearch) w/o PAM being setup, but to get users to auth via LDAP you will need PAM setup for LDAP. A basic ldapsearch just shows you have the ldap lib and client tools packages installed (ie. yum install openldap openldap-clients) and can reach the LDAP directory server(s). Its a good step in the setup or troubleshooting process.
    – Ernie
    Oct 13, 2017 at 0:39

3 Answers 3


Use ldapsearch. It will return an error if you cannot query the LDAP Server.

The syntax for using ldapsearch:

ldapsearch -x -LLL -h [host] -D [user] -w [password] -b [base DN] -s sub "([filter])" [attribute list]

A simple example

$ ldapsearch -x -LLL -h host.example.com -D user -w password -b"dc=ad,dc=example,dc=com" -s sub "(objectClass=user)" givenName

Please see this link: http://randomerror.wordpress.com/2009/10/16/quick-tip-how-to-search-in-windows-active-directory-from-linux-with-ldapsearch/

Edit: It seems you don't have pam configured corectlly for gdm/xdm here is an example how to do it: http://pastebin.com/TDK4KWRV

Note for ldapsearch >= 2.5: If using ldapsearch from openldap, the options -h and -p were dropped in version 2.5. Use -H instead:

$ ldapsearch -H ldapuri -D binddn -w password -b searchbase filter

where ldapuri could contain protocol/host/port fields, e.g.: ldaps://ldap.example.org:636

  • I'm using this command: ldapsearch -h hostname -x -b "dc=example,dc=com" 'uid=user' and it returns that user info from the LDAP database. But I'm not able to login to the desktop via LDAP authentication.
    – FELDAP
    Nov 28, 2012 at 10:46
  • If your server doesn't have any error, then probably is from your client. Please take a look on the auth.log and see what is there related to ldap.
    – Sacx
    Nov 28, 2012 at 10:48
  • Yes, I guess its the client. Its not even searching for the LDAP server. What should be done to make the client to lookup LDAP server for authentication? I have edited the /etc/pam.d/system-auth. You can check here: pastebin.com/jQjN7cYU
    – FELDAP
    Nov 28, 2012 at 11:14
  • 2
    Use ldapwhoami with correct parameters and try to authenticate with your user.
    – Sacx
    Nov 28, 2012 at 11:16
  • do you followed a tutorial to prepare the client for gdm/xdm authentication ?
    – Sacx
    Nov 28, 2012 at 11:21

To know if my server and clients settings are correct I use this:

ldapsearch -x -b "uid=username,ou=people,dc=example,dc=com"

the answer will be something like this on success:

# extended LDIF
# LDAPv3
# base <uid=username,ou=people,dc=example,dc=com> with scope subtree
# filter: (objectclass=*)
# requesting: ALL

# username, people, example.com
dn: uid=username,ou=people,dc=example,dc=com
cn: User Name
uid: username
uidNumber: 1050
loginShell: /bin/bash
homeDirectory: /home/webminder
gidNumber: 1030
objectClass: posixAccount
objectClass: shadowAccount
objectClass: person
objectClass: inetOrgPerson
gecos: User Name
sn: User Name

# search result
search: 2
result: 0 Success

# numResponses: 2
# numEntries: 1

you can use different filters. I only have one server on my network


Your problem is not LDAP, It's PAM.

As noted in the comments on Sacx's answer you probably do not have the console login application (usually the PAM system, xdm, gdm, etc. service(s)) configured to consult LDAP for authenticating users.

You should review the PAM documentation for more information on how to set this up.

  • I have already configured those files, yet its not working. You can check the files I posted in the above comments. LDAP really lacks its documents.
    – FELDAP
    Dec 2, 2012 at 7:25

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .