LDAP Troubleshooting for Administrators

Common Problems & Workflows


Connection refused

If you are getting Connection Refused errors when trying to connect to the LDAP server please double-check the LDAP port and encryption settings used by GitLab. Common combinations are encryption: 'plain' and port: 389, OR encryption: 'simple_tls' and port: 636.

Connection times out

If GitLab cannot reach your LDAP endpoint, you will see a message like this:

Could not authenticate you from Ldapmain because "Connection timed out - user specified timeout".

If your configured LDAP provider and/or endpoint is offline or otherwise unreachable by GitLab, no LDAP user will be able to authenticate and sign-in. GitLab does not cache or store credentials for LDAP users to provide authentication during an LDAP outage.

Contact your LDAP provider or administrator if you are seeing this error.

Referral error

If you see LDAP search error: Referral in the logs, or when troubleshooting LDAP Group Sync, this error may indicate a configuration problem. The LDAP configuration /etc/gitlab/gitlab.rb (Omnibus) or config/gitlab.yml (source) is in YAML format and is sensitive to indentation. Check that group_base and admin_group configuration keys are indented 2 spaces past the server identifier. The default identifier is main and an example snippet looks like the following:

main: # 'main' is the GitLab 'provider ID' of this LDAP server
  label: 'LDAP'
  host: 'ldap.example.com'
  group_base: 'cn=my_group,ou=groups,dc=example,dc=com'
  admin_group: 'my_admin_group'

Query LDAP

The following allows you to perform a search in LDAP using the rails console. Depending on what you’re trying to do, it may make more sense to query a user or a group directly, or even use ldapsearch instead.

adapter = Gitlab::Auth::Ldap::Adapter.new('ldapmain')
options = {
    # :base is required
    # use .base or .group_base
    base: adapter.config.group_base,

    # :filter is optional
    # 'cn' looks for all "cn"s under :base
    # '*' is the search string - here, it's a wildcard
    filter: Net::Ldap::Filter.eq('cn', '*'),

    # :attributes is optional
    # the attributes we want to get returned
    attributes: %w(dn cn memberuid member submember uniquemember memberof)

For examples of how this is run, review the Adapter module.

User sign-ins

No users are found

If you’ve confirmed that a connection to LDAP can be established but GitLab doesn’t show you LDAP users in the output, one of the following is most likely true:

  • The bind_dn user doesn’t have enough permissions to traverse the user tree.
  • The user(s) don’t fall under the configured base.
  • The configured user_filter blocks access to the user(s).

In this case, you con confirm which of the above is true using ldapsearch with the existing LDAP configuration in your /etc/gitlab/gitlab.rb.

User(s) cannot sign-in

A user can have trouble signing in for any number of reasons. To get started, here are some questions to ask yourself:

  • Does the user fall under the configured base in LDAP? The user must fall under this base to sign-in.
  • Does the user pass through the configured user_filter? If one is not configured, this question can be ignored. If it is, then the user must also pass through this filter to be allowed to sign-in.

If the above are both okay, the next place to look for the problem is the logs themselves while reproducing the issue.

  • Ask the user to sign-in and let it fail.
  • Look through the output for any errors or other messages about the sign-in. You may see one of the other error messages on this page, in which case that section can help resolve the issue.

If the logs don’t lead to the root of the problem, use the rails console to query this user to see if GitLab can read this user on the LDAP server.

It can also be helpful to debug a user sync to investigate further.

Invalid credentials on sign-in

If that the sign-in credentials used are accurate on LDAP, ensure the following are true for the user in question:

  • Make sure the user you are binding with has enough permissions to read the user’s tree and traverse it.
  • Check that the user_filter is not blocking otherwise valid users.
  • Run an LDAP check command to make sure that the LDAP settings are correct and GitLab can see your users.

Email has already been taken

A user tries to sign-in with the correct LDAP credentials, is denied access, and the production.log shows an error that looks like this:

(LDAP) Error saving user <USER DN> (email@example.com): ["Email has already been taken"]

This error is referring to the email address in LDAP, email@example.com. Email addresses must be unique in GitLab and LDAP links to a user’s primary email (as opposed to any of their possibly-numerous secondary emails). Another user (or even the same user) has the email email@example.com set as a secondary email, which is throwing this error.

We can check where this conflicting email address is coming from using the rails console. Once in the console, run the following:

# This searches for an email among the primary AND secondary emails
user = User.find_by_any_email('email@example.com')

This will show you which user has this email address. One of two steps will have to be taken here:

  • To create a new GitLab user/username for this user when signing in with LDAP, remove the secondary email to remove the conflict.
  • To use an existing GitLab user/username for this user to use with LDAP, remove this email as a secondary email and make it a primary one so GitLab will associate this profile to the LDAP identity.

The user can do either of these steps in their profile or an admin can do it.

Debug LDAP user filter

ldapsearch allows you to test your configured user filter to confirm that it returns the users you expect it to return.

ldapsearch -H ldaps://$host:$port -D "$bind_dn" -y bind_dn_password.txt  -b "$base" "$user_filter" sAMAccountName
  • Variables beginning with a $ refer to a variable from the LDAP section of your configuration file.
  • Replace ldaps:// with ldap:// if you are using the plain authentication method. Port 389 is the default ldap:// port and 636 is the default ldaps:// port.
  • We are assuming the password for the bind_dn user is in bind_dn_password.txt.

Sync all users

The output from a manual user sync can show you what happens when GitLab tries to sync its users against LDAP. Enter the rails console and then run:

Rails.logger.level = Logger::DEBUG


Next, learn how to read the output.

Example console output after a user sync

The output from a manual user sync will be very verbose, and a single user’s successful sync can look like this:

Syncing user John, email@example.com
  Identity Load (0.9ms)  SELECT  "identities".* FROM "identities" WHERE "identities"."user_id" = 20 AND (provider LIKE 'ldap%') LIMIT 1
Instantiating Gitlab::Auth::Ldap::Person with LDIF:
dn: cn=John Smith,ou=people,dc=example,dc=com
cn: John Smith
mail: email@example.com
memberof: cn=admin_staff,ou=people,dc=example,dc=com
uid: John

  UserSyncedAttributesMetadata Load (0.9ms)  SELECT  "user_synced_attributes_metadata".* FROM "user_synced_attributes_metadata" WHERE "user_synced_attributes_metadata"."user_id" = 20 LIMIT 1
   (0.3ms)  BEGIN
  Namespace Load (1.0ms)  SELECT  "namespaces".* FROM "namespaces" WHERE "namespaces"."owner_id" = 20 AND "namespaces"."type" IS NULL LIMIT 1
  Route Load (0.8ms)  SELECT  "routes".* FROM "routes" WHERE "routes"."source_id" = 27 AND "routes"."source_type" = 'Namespace' LIMIT 1
  Ci::Runner Load (1.1ms)  SELECT "ci_runners".* FROM "ci_runners" INNER JOIN "ci_runner_namespaces" ON "ci_runners"."id" = "ci_runner_namespaces"."runner_id" WHERE "ci_runner_namespaces"."namespace_id" = 27
   (0.7ms)  COMMIT
   (0.4ms)  BEGIN
  Route Load (0.8ms)  SELECT "routes".* FROM "routes" WHERE (LOWER("routes"."path") = LOWER('John'))
  Namespace Load (1.0ms)  SELECT  "namespaces".* FROM "namespaces" WHERE "namespaces"."id" = 27 LIMIT 1
  Route Exists (0.9ms)  SELECT  1 AS one FROM "routes" WHERE LOWER("routes"."path") = LOWER('John') AND "routes"."id" != 50 LIMIT 1
  User Update (1.1ms)  UPDATE "users" SET "updated_at" = '2019-10-17 14:40:59.751685', "last_credential_check_at" = '2019-10-17 14:40:59.738714' WHERE "users"."id" = 20

There’s a lot here, so let’s go over what could be helpful when debugging.

First, GitLab will look for all users that have previously signed in with LDAP and iterate on them. Each user’s sync will start with the following line that contains the user’s username and email, as they exist in GitLab now:

Syncing user John, email@example.com

If you don’t find a particular user’s GitLab email in the output, then that user hasn’t signed in with LDAP yet.

Next, GitLab searches its identities table for the existing link between this user and the configured LDAP provider(s):

  Identity Load (0.9ms)  SELECT  "identities".* FROM "identities" WHERE "identities"."user_id" = 20 AND (provider LIKE 'ldap%') LIMIT 1

The identity object will have the DN that GitLab will use to look for the user in LDAP. If the DN isn’t found, the email is used instead. We can see that this user is found in LDAP:

Instantiating Gitlab::Auth::Ldap::Person with LDIF:
dn: cn=John Smith,ou=people,dc=example,dc=com
cn: John Smith
mail: email@example.com
memberof: cn=admin_staff,ou=people,dc=example,dc=com
uid: John

If the user wasn’t found in LDAP with either the DN or email, you may see the following message instead:

LDAP search error: No Such Object

…in which case the user will be blocked:

  User Update (0.4ms)  UPDATE "users" SET "state" = $1, "updated_at" = $2 WHERE "users"."id" = $3  [["state", "ldap_blocked"], ["updated_at", "2019-10-18 15:46:22.902177"], ["id", 20]]

Once the user is found in LDAP the rest of the output will update the GitLab database with any changes.

Query a user in LDAP

This will test that GitLab can reach out to LDAP and read a particular user. It can expose potential errors connecting to and/or querying LDAP that may seem to fail silently in the GitLab UI.

Rails.logger.level = Logger::DEBUG

adapter = Gitlab::Auth::Ldap::Adapter.new('ldapmain') # If `main` is the LDAP provider
Gitlab::Auth::Ldap::Person.find_by_uid('<uid>', adapter)

Group memberships

Membership(s) not granted

Sometimes you may think a particular user should be added to a GitLab group via LDAP group sync, but for some reason it’s not happening. There are several things to check to debug the situation.

  • Ensure LDAP configuration has a group_base specified. This configuration is required for group sync to work properly.
  • Ensure the correct LDAP group link is added to the GitLab group.
  • Check that the user has an LDAP identity:
    1. Sign in to GitLab as an administrator user.
    2. Navigate to Admin area -> Users.
    3. Search for the user
    4. Open the user, by clicking on their name. Do not click ‘Edit’.
    5. Navigate to the Identities tab. There should be an LDAP identity with an LDAP DN as the ‘Identifier’. If not, this user hasn’t signed in with LDAP yet and must do so first.
  • You’ve waited an hour or the configured interval for the group to sync. To speed up the process, either go to the GitLab group Settings -> Members and press Sync now (sync one group) or run the group sync Rake task (sync all groups).

If all of the above looks good, jump in to a little more advanced debugging in the rails console.

  1. Enter the rails console.
  2. Choose a GitLab group to test with. This group should have an LDAP group link already configured.
  3. Enable debug logging, find the above GitLab group, and sync it with LDAP.
  4. Look through the output of the sync. See example log output for how to read the output.
  5. If you still aren’t able to see why the user isn’t being added, query the LDAP group directly to see what members are listed.
  6. Is the user’s DN or UID in one of the lists from the above output? One of the DNs or UIDs here should match the ‘Identifier’ from the LDAP identity checked earlier. If it doesn’t, the user does not appear to be in the LDAP group.

Admin privileges not granted

When Administrator sync has been configured but the configured users aren’t granted the correct admin privileges, confirm the following are true:

  • A group_base is also configured.
  • The configured admin_group in the gitlab.rb is a CN, rather than a DN or an array.
  • This CN falls under the scope of the configured group_base.
  • The members of the admin_group have already signed into GitLab with their LDAP credentials. GitLab will only grant this admin access to the users whose accounts are already connected to LDAP.

If all the above are true and the users are still not getting access, run a manual group sync in the rails console and look through the output to see what happens when GitLab syncs the admin_group.

Sync all groups

NOTE: To sync all groups manually when debugging is unnecessary, use the Rake task instead.

The output from a manual group sync can show you what happens when GitLab syncs its LDAP group memberships against LDAP.

Rails.logger.level = Logger::DEBUG


Next, learn how to read the output.

Example console output after a group sync

Like the output from the user sync, the output from the manual group sync will also be very verbose. However, it contains lots of helpful information.

Indicates the point where syncing actually begins:

Started syncing 'ldapmain' provider for 'my_group' group

The following entry shows an array of all user DNs GitLab sees in the LDAP server. Note that these are the users for a single LDAP group, not a GitLab group. If you have multiple LDAP groups linked to this GitLab group, you will see multiple log entries like this - one for each LDAP group. If you don’t see an LDAP user DN in this log entry, LDAP is not returning the user when we do the lookup. Verify the user is actually in the LDAP group.

Members in 'ldap_group_1' LDAP group: ["uid=john0,ou=people,dc=example,dc=com",
"uid=mary0,ou=people,dc=example,dc=com", "uid=john1,ou=people,dc=example,dc=com",
"uid=mary1,ou=people,dc=example,dc=com", "uid=john2,ou=people,dc=example,dc=com",
"uid=mary2,ou=people,dc=example,dc=com", "uid=john3,ou=people,dc=example,dc=com",
"uid=mary3,ou=people,dc=example,dc=com", "uid=john4,ou=people,dc=example,dc=com",

Shortly after each of the above entries, you will see a hash of resolved member access levels. This hash represents all user DNs GitLab thinks should have access to this group, and at which access level (role). This hash is additive, and more DNs may be added, or existing entries modified, based on additional LDAP group lookups. The very last occurrence of this entry should indicate exactly which users GitLab believes should be added to the group.

Note: 10 is ‘Guest’, 20 is ‘Reporter’, 30 is ‘Developer’, 40 is ‘Maintainer’ and 50 is ‘Owner’.
Resolved 'my_group' group member access: {"uid=john0,ou=people,dc=example,dc=com"=>30,
"uid=mary0,ou=people,dc=example,dc=com"=>30, "uid=john1,ou=people,dc=example,dc=com"=>30,
"uid=mary1,ou=people,dc=example,dc=com"=>30, "uid=john2,ou=people,dc=example,dc=com"=>30,
"uid=mary2,ou=people,dc=example,dc=com"=>30, "uid=john3,ou=people,dc=example,dc=com"=>30,
"uid=mary3,ou=people,dc=example,dc=com"=>30, "uid=john4,ou=people,dc=example,dc=com"=>30,

It’s not uncommon to see warnings like the following. These indicate that GitLab would have added the user to a group, but the user could not be found in GitLab. Usually this is not a cause for concern.

If you think a particular user should already exist in GitLab, but you’re seeing this entry, it could be due to a mismatched DN stored in GitLab. See User DN and/or email have changed to update the user’s LDAP identity.

User with DN `uid=john0,ou=people,dc=example,dc=com` should have access
to 'my_group' group but there is no user in GitLab with that
identity. Membership will be updated once the user signs in for
the first time.

Finally, the following entry says syncing has finished for this group:

Finished syncing all providers for 'my_group' group

Once all the configured group links have been synchronized, GitLab will look for any Administrators or External users to sync:

Syncing admin users for 'ldapmain' provider

The output will look similar to what happens with a single group, and then this line will indicate the sync is finished:

Finished syncing admin users for 'ldapmain' provider

If admin sync is not configured, you’ll see a message stating as such:

No `admin_group` configured for 'ldapmain' provider. Skipping

Sync one group

Syncing all groups can produce a lot of noise in the output, which can be distracting when you’re only interested in troubleshooting the memberships of a single GitLab group. In that case, here’s how you can just sync this group and see its debug output:

Rails.logger.level = Logger::DEBUG

# Find the GitLab group.
# If the output is `nil`, the group could not be found.
# If a bunch of group attributes are in the output, your group was found successfully.
group = Group.find_by(name: 'my_gitlab_group')

# Sync this group against LDAP

The output will be similar to that you’d get from syncing all groups.

Query a group in LDAP

When you’d like to confirm that GitLab can read a LDAP group and see all its members, you can run the following:

# Find the adapter and the group itself
adapter = Gitlab::Auth::Ldap::Adapter.new('ldapmain') # If `main` is the LDAP provider
ldap_group = EE::Gitlab::Auth::Ldap::Group.find_by_cn('group_cn_here', adapter)

# Find the members of the LDAP group

User DN or/and email have changed

When an LDAP user is created in GitLab, their LDAP DN is stored for later reference.

If GitLab cannot find a user by their DN, it will fall back to finding the user by their email. If the lookup is successful, GitLab will update the stored DN to the new value so both values will now match what’s in LDAP.

If the email has changed and the DN has not, GitLab will find the user with the DN and update its own record of the user’s email to match the one in LDAP.

However, if the primary email and the DN change in LDAP, then GitLab will have no way of identifying the correct LDAP record of the user and, as a result, the user will be blocked. To rectify this, the user’s existing profile will have to be updated with at least one of the new values (primary email or DN) so the LDAP record can be found.

The following script will update the emails for all provided users so they won’t be blocked or unable to access their accounts.

NOTE: The following script will require that any new accounts with the new email address are removed first. This is because emails have to be unique in GitLab.

Go to the rails console and then run:

# Each entry will have to include the old username and the new email
emails = {

emails.each do |username, email|
  user = User.find_by_username(username)
  user.email = email

You can then run a UserSync to sync the latest DN for each of these users.

Debugging Tools

LDAP check

The Rake task to check LDAP is a valuable tool to help determine whether GitLab can successfully establish a connection to LDAP and can get so far as to even read users.

If a connection can’t be established, it is likely either because of a problem with your configuration or a firewall blocking the connection.

  • Ensure you don’t have a firewall blocking the connection, and that the LDAP server is accessible to the GitLab host.
  • Look for an error message in the Rake check output, which may lead to your LDAP configuration to confirm that the configuration values (specifically host, port, bind_dn, and password) are correct.
  • Look for errors in the logs to further debug connection failures.

If GitLab can successfully connect to LDAP but doesn’t return any users, see what to do when no users are found.

GitLab logs

If a user account is blocked or unblocked due to the LDAP configuration, a message will be logged to application.log.

If there is an unexpected error during an LDAP lookup (configuration error, timeout), the sign-in is rejected and a message will be logged to production.log.


ldapsearch is a utility that will allow you to query your LDAP server. You can use it to test your LDAP settings and ensure that the settings you’re using will get you the results you expect.

When using ldapsearch, be sure to use the same settings you’ve already specified in your gitlab.rb configuration so you can confirm what happens when those exact settings are used.

Running this command on the GitLab host will also help confirm that there’s no obstruction between the GitLab host and LDAP.

For example, consider the following GitLab configuration:

gitlab_rails['ldap_servers'] = YAML.load <<-'EOS' # remember to close this block with 'EOS' below
   main: # 'main' is the GitLab 'provider ID' of this LDAP server
     label: 'LDAP'
     host: ''
     port: 389
     uid: 'uid'
     encryption: 'plain'
     bind_dn: 'cn=admin,dc=ldap-testing,dc=example,dc=com'
     password: 'Password1'
     active_directory: true
     allow_username_or_email_login: false
     block_auto_created_users: false
     base: 'dc=ldap-testing,dc=example,dc=com'
     user_filter: ''
       username: ['uid', 'userid', 'sAMAccountName']
       email:    ['mail', 'email', 'userPrincipalName']
       name:       'cn'
       first_name: 'givenName'
       last_name:  'sn'
     group_base: 'ou=groups,dc=ldap-testing,dc=example,dc=com'
     admin_group: 'gitlab_admin'

You would run the following ldapsearch to find the bind_dn user:

ldapsearch -D "cn=admin,dc=ldap-testing,dc=example,dc=com" \
  -w Password1 \
  -p 389 \
  -h \
  -b "dc=ldap-testing,dc=example,dc=com"

Note that the bind_dn, password, port, host, and base are all identical to what’s configured in the gitlab.rb.

Please see the official ldapsearch documentation for more.

Using AdFind (Windows)

You can use the AdFind utility (on Windows based systems) to test that your LDAP server is accessible and authentication is working correctly. This is a freeware utility built by Joe Richards.

Return all objects

You can use the filter objectclass=* to return all directory objects.

adfind -h ad.example.org:636 -ssl -u "CN=GitLabSRV,CN=Users,DC=GitLab,DC=org" -up Password1 -b "OU=GitLab INT,DC=GitLab,DC=org" -f (objectClass=*)

Return single object using filter

You can also retrieve a single object by specifying the object name or full DN. In this example we specify the object name only CN=Leroy Fox.

adfind -h ad.example.org:636 -ssl -u "CN=GitLabSRV,CN=Users,DC=GitLab,DC=org" -up Password1 -b "OU=GitLab INT,DC=GitLab,DC=org" -f (&(objectcategory=person)(CN=Leroy Fox))

Rails console

CAUTION: Please note that it is very easy to create, read, modify, and destroy data on the rails console, so please be sure to run commands exactly as listed.

The rails console is a valuable tool to help debug LDAP problems. It allows you to directly interact with the application by running commands and seeing how GitLab responds to them.

Please refer to this guide for instructions on how to use the rails console.

Enable debug output

This will provide debug output that will be useful to see what GitLab is doing and with what. This value is not persisted, and will only be enabled for this session in the rails console.

To enable debug output in the rails console, enter the rails console and run:

Rails.logger.level = Logger::DEBUG