How to Integrate RHEL 7 or CentOS 7 with Windows Active Directory

In Most of the Organizations users and groups are created and managed on Windows Active Directory.  We can integrate our RHEL 7 and CentOS 7 servers with AD(Active Directory) for authenticate purpose. In other words we can join our CentOS 7 and RHEL 7 Server on Windows Domain so that system admins can login to these Linux servers with AD credentials. While creating UNIX users on AD we can map these users to a specific group so that level of access is controlled centrally from AD.

In this article we discuss how to integrate CentOS 7.x & RHEL 7.x with AD(Windows Server 2008 R2 & Windows Server 2012 R2). Following steps are applicable for both CentOS 7 and RHEL 7.

Step:1 Install the required packages using yum command

Use the yum command to install following packages from the command line.

[[email protected] ~]# yum install sssd realmd oddjob oddjob-mkhomedir adcli samba-common samba-common-tools krb5-workstation openldap-clients policycoreutils-python

Update the /etc/hosts file and /etc/resolv.conf so that dns name or hostname of AD server gets resolved correctly. In my case AD server hostname is “adserver.example.com“, so place the below line in /etc/hosts file

192.168.0.151    adserver.example.com  adserver

Contents of resolv.conf should be something like below. Just replace the domain name and ip address of dns server as per your setup

[[email protected] ~]# cat /etc/resolv.conf
search example.com
nameserver 192.168.0.151
[[email protected]ervera ~]#

Step:2 Now Join Windows Domain or Integrate with AD using realm command

When we install above required packages then realm command will be available. We will use beneath realm command to integrate CentOS 7 or RHEL 7 with AD via the user “tech”. tech is a bind user which have required privileges on AD or  we can also administrator user of AD Server for integration purpose.

[[email protected] ~]# realm join --user=tech adserver.example.com
Password for tech:
[[email protected] ~]#

Now verify whether our server has joined the Windows domain or not. Simply run the command ‘realm list

 [[email protected] ~]# realm list
example.com
  type: kerberos
  realm-name: EXAMPLE.COM
  domain-name: example.com
  configured: kerberos-member
  server-software: active-directory
  client-software: sssd
  required-package: oddjob
  required-package: oddjob-mkhomedir
  required-package: sssd
  required-package: adcli
  required-package: samba-common-tools
  login-formats: %[email protected]
  login-policy: allow-realm-logins
[[email protected] ~]#

Whenever we run ‘realm join’ command it will automatically configure ‘/etc/sssd/sssd.conf‘ file.

Step:3 Check and Verify  AD users on REHL 7 or CentOS 7 Servers

With ‘id‘ command on Linux we can verify the user’s uid and gid and their group information. At this point of time our server is now the part of windows domain. Use below command to verify AD users details.

[[email protected] ~]# id [email protected]
uid=1997801106([email protected]) gid=1997800513(domain [email protected]) groups=1997800513(domain [email protected])
[[email protected] ~]#

You might have noticed in above command that i have mentioned domain name as well along with user name because this is controlled by ‘/etc/sssd/sssd.conf’ file. If we execute id command without domain name then we will not get any details for user.

[[email protected] ~]# id linuxtechi
id: linuxtechi: no such user
[[email protected] ~]#

We can change this behavior by editing the file /etc/sssd/sssd.conf.

Change the following parameters from

use_fully_qualified_names = True
fallback_homedir = /home/%[email protected]%d

to

use_fully_qualified_names = False
fallback_homedir = /home/%u

Restart the sssd service using following systemctl command

[[email protected] ~]# systemctl restart sssd
[[email protected] ~]# systemctl daemon-reload

Now run the id command and see whether you are able get AD user details without mentioning domain name

[[email protected] ~]# id linuxtechi
uid=1997801106(linuxtechi) gid=1997800513(domain users) groups=1997800513(domain users)
[[email protected] ~]#

Let’s try ssh CentOS 7 or RHEL 7 Server with AD credentials

[[email protected] ~]# ssh [email protected]
[email protected]'s password:
Last login: Fri Mar  3 10:18:41 2017 from serverb.example.com
[[email protected] ~]$ id
uid=1997801106(linuxtechi) gid=1997800513(domain users) groups=1997800513(domain users)
[[email protected] ~]$ pwd
/home/linuxtechi
[[email protected] ~]$

Step:4 Sudo rights for AD users on CentOS 7 or RHEL 7

In case you want to configure sudo rights for AD users then the best way is to create a group on AD with name sudoers and add Linux/UNIX users in that group and on Linux Server create a file with name “sudoers” under the folder /etc/sudoers.d/

Put the following content in the file.

[[email protected] ~]# cat /etc/sudoers.d/sudoers
%sudoers    ALL=(ALL)       ALL
[[email protected] ~]#

In my case I have given all the rights to the users which are part of sudoers group. Once your done with these changes re-login to your server with AD credentials and see whether user is part of sudoers group.

AD-User-Sudoers-Group-Linux

That’s all from this article, Hope you guys got an idea how to join RHEL or CentOS server with Windows Domain. Please share your feedback and valuable comments.

38 Responses

  1. mossholderm says:

    One pedantic complaint… in your last screenshot, you execute “sudo su -” … you should really just be using “sudo -i”.

  2. Tyler says:

    Do you know how to make JUST authentication work with CentOS 7? I’m trying to get some linux servers from one domain, to be able to authenticate to another, so I don’t want to join the domain. I was able to do this with CentOS 5 and 6, but I haven’t been able to get it to work with 7. Any thoughts?

  3. Bob says:

    Great info, thanks for posting. One thing I’m trying to figure out is how to restrict user logins based on AD group membership. Any ideas here? I saw one article referring to pam_access and nologin and editing the access.conf file but so far no luck. All domain members can still SSH to the host.

    Thanks again,

    Bob

    • Hi Bob,

      To restrict user login to CentOS 7 / RHEL 7 Server that are on window domain, use the following steps:

      1) Create the Security Groups on AD ( like linuxadmins”)
      2) Add the domain users (which to want to allow login) to this security group.
      3) MAP the security group to CentOS / RHEL 7 Server by adding the following line in the file (/etc/sssd/sssd.conf)

      [sssd]
      ……..

      realm permit -g [email protected]

      example

      realm permit -g [email protected]

      4) Restart the sssd service

      5) If you want to control rights as well , then you can place the ad security group in sudoers file, example is shown below

      %[email protected] ALL=(ALL) ALL

  4. Sandeep Kumar says:

    Hi Pradeep,

    First of all thank you very much for posting this valuable information, it’s really very helpfull.

    I am trying to configure the AD authentication and facing one issue while following your article.
    Let me elaborate more-

    1- I have installed all the required packages as mentioned in the article.
    2- I have all the connectivity in place and my RHEL7 server is able to connect with AD server with IP and FQDN.
    3- Next is when I execute the “realm discover” or “realm discover domainname” I am getting “No such realm found:” error.

    [[email protected] ~]# realm discover [email protected]
    realm: No such realm found: [email protected]

    Please help me to troubleshoot the issue.

    Thanks in Advance.

  5. Naga says:

    Hello Pradeep, realm join with a user was successful but this is not able to identify any users. SSSD service is giving me this error:

    GSSAPI Error: Unspecified GSS failure. Minor code may provide more information (Server not found in Kerberos database)

    Any idea why this is happening? Do I need to configure anything in /etc/krb5.conf?

  6. Tom says:

    Thank you for posting this article! These instructions are for RHEL7/CentOS7. Do you know if it would work on RHEL6 or 5?

  7. Hugo Santos says:

    Hello. I’ve installes sssd on a Centos7 server and i’m able to login using may Active Directory credentials, however the id command does not resolve the group names of the AD . Denying me the possiblity of restrict the authentication based on an AD group , because the declared group under sssd.conf cannot be found.

    Any ideas ?

  8. yousuf says:

    Hi ,

    The above one i have tried which is working Fine, we are able to login with the help of AD users on linux Machine , But we have a different Requirement in my company, we configured Apache website which is in php( index.php) on Linux Server For User Authentication on Php Application (Username:- , Password) we are able to authenticate from mysql Database But we need the Authentication from the Active Directory Also, if there a way without configurig ldap server we can do …? Plz help if possible

  9. Chris says:

    Hi,

    The above steps worked great for me, but there’s a couple problems I’ve run into. My company is migrating from NIS to AD. Our home directories are owned by our NIS accounts, which is mounted using autofs settings from NIS. However, I cannot create new files or modify existing ones in my home directory because my AD account isn’t the owner. How can I change my UID in AD to match my NIS UID?

  10. Arul Kumar says:

    Hello,

    We have done almost all SSSD configuration but while coneecting AD user in Linux “” su – ad user” getting error

    “” File size limit exceeded (core dumped “””

    • Wai Htut Paing says:

      Me too !

      My samba (centos server) was jointed to AD via realm list.
      But I couldn’t verify AD user on centos with id command.
      it shown no such user.

  11. Chip says:

    Very helpful – thank you!

    Do you have a similar article for integrating samba and active directory authentication? I’d like to be able to share out the home directories on the centos server of the active directory users who have logged in and I am running into a wall.

  12. Nitiratna says:

    First of all, Big thank you.

    Q.Is there any way to control UID while creating user on AD?

  13. Mat Des says:

    Have you find any solution pour your samba issue with an existing AD? I’m looking for the same thing. Thanks

  14. Artura says:

    getent passwd; getent group; doesn’t work after this tutorial,

    You need to add:
    enumerate = true
    in your sssd.conf file (under: [domain/])

  15. Brice Miram says:

    it’s works very well with windows server 2012 R2.
    Thank you for this beautiful tutorial.

  16. Dave says:

    This is fantastic – thank you! Now, what about integrating Samba authentication with this method of AD integration? I cannot seem to get this to work.

  17. Manoj Malviya says:

    I have installed it on aws but when i try to ssh it it say permission denied i have 3 4 times but still showing same issue..

    Any solution for this error

  18. Zia says:

    I tried the solution and it worked for me now I have a different issue/question.

    I added my linux server to subA.domain.com. I also want to allow domain.com and subB.domain.com users to be able to login as well.

    how can i do that

  19. Christopher says:

    Hi i have strange case with Centos 7. I had join the domain, i can log on AD users but there is no DNS entry of my Centos 7 in AD DNS. I had updated /etc/sssd/sssd.conf with dyndns_update = True, but it don’t help. Any suggestions?

  20. Ansuman says:

    I am getting this error while running realm join command:

    * Wrote out krb5.conf snippet to /var/cache/realmd/adcli-krb5-WkIz9P/krb5.d/adcli-krb5-conf-ObFF3n
    ! Couldn’t get kerberos ticket for: : Cannot contact any KDC for realm ”

  21. Wai Htut Paing says:

    id: [email protected]: no such user

    my centos joined to AD .
    Some lines of realm list are …..
    configured: kerberos-member
    server-software: active-directory
    client-software: sssd
    required-package: oddjob
    required-package: oddjob-mkhomedir
    required-package: sssd
    required-package: adcli
    required-package: samba-common-tools
    login-formats: %U
    login-policy: allow-realm-logins

    But I couldn’t verify ad user on centos.
    If you don’t mind, please help to me to solve it.

  22. Prince Trivedi says:

    Hello Pradeep,

    After executing realm list command when I am trying to execute the command id [email protected], It is giving me an error, realm : no such user found.

    Kindly help me to resolve this issue

  23. Vincent says:

    Hello Pradeep.
    We recently integrated AD to centos 7.x . Users can login but after login it says /home/user/.bash_profile: permission denied.
    Please advise

  24. Eduardo Cavalcante says:

    If the Active Directory is OFFLINE, will the users still be able to connect to the Linux servers using the account that is provided by AD?

  25. Brian says:

    I ran your above commands to join to the domain and I can query ID and realm list. But, I cannot log into the RHEL 7 server via SSH. Did I miss something?

  26. Jonah Smethonson says:

    A great post, thank you very much. To add, it would be nice to configure the NTP client. The idea is that the NTP client synchronizes time with the domain controller (DC). Here is an interesting guide to check: ‘https://www.sysadmit.com/2019/11/linux-anadir-equipo-al-dominio-windows.html’

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