Add a Red Hat Enterprise Linux 6 system to Microsoft Active Directory

UPDATE!! .. This article also works perfectly on Windows 2012 Server as well as Windows Server 2008. The process is exactly the same.

I’ve had countless numbers of people ask me over the years how to add a Linux system to Active Directory.

Here is a really quick and simple way to do it using Windbind for userlookups, and Kerberos for authentication.

In this example, I will be using the below details

Windows Domain Name:         rmohan.com
Windows Domain NetBIOS Name: RMOHAN
Domain Controller:           dc1.rmohan.com
Client Server name:          server01.rmohan.com

Setup

1. Firstly, install the necessary components.

yum install -y samba-winbind samba-winbind-clients oddjob-mkhomedir pam_krb5 krb5-workstation

2. Make sure OddJobd is running at Startup. This is only for Red Hat Enterprise Linux 6 and other Red Hat based Operating systems.

Red Hat Enterprise Linux 5 will use pam_mkhomedir. pam_mkhomedir has SELinux issues at present, so oddjobd is the way to go.

chkconfig oddjobd on

3. Set authconfig to point to the relevant systems for Authentication.
Note: If you do not wish your users to log into your server via a shell, set –winbindtemplateshell to –winbindtemplateshell=/sbin/nologin

authconfig –update –kickstart –enablewinbind –smbsecurity=ads –smbworkgroup=RMOHAN –smbrealm=rmohan.com –winbindtemplatehomedir=/home/%U –winbindtemplateshell=/bin/bash –enablewinbindusedefaultdomain –enablelocauthorize –enablekrb5 –krb5realm=RMOHAN.COM –enablekrb5kdcdns –enablekrb5realmdns –enablepamaccess

4. Just like in Windows, Add your system to the domain. Here I have used the Domain Administrator account, but any account with enough rights to add a system to the domain will suffice.

[root@server ~]# net ads join -U Administrator
Enter Administrator’s password:
Using short domain name — RMOHAN
Joined ‘server’ to realm ‘rmohan.com’

Note: As you are now dealing with Active Directory, it now becomes time sensitive. Make sure your system clock is pointing to one of your Domain Controllers as the RMOHANP server.

Otherwise you will end up with errors like this when you try to add the system to the domain.

[root@server ~]# net ads join -U Administrator
Enter Administrator’s password:
Using short domain name — RMOHAN
Joined ‘SERVER’ to realm ‘rmohan.com’
[2012/07/06 17:24:04.397769,  0] libads/kerberos.c:333(ads_kinit_password)
kerberos_kinit_password SERVER$@RMOHAN.EXAMPLE.COM failed: Clock skew too great
[root@server ~]#

5. Configure Winbind Backend
The default Winbind backend is great for single systems being added to Active Directory, however if you are in a very large Linux estate like I usually am, you will need to change the backend to ensure that all UID’s/GID’s match across all your systems.

To do this, add the below two lines to your global Samba configuration. Replace “RMOHAN” with your own Domain name.

idmap config RMOHAN:backend = rid
idmap config RMOHAN:range = 10000000-19999999
kerberos method = dedicated keytab
dedicated keytab file=/etc/krb5.keytab

Just so we are on the same page, my global configuration now looks like this

workgroup = RMOHAN
realm = RMOHAN.EXAMPLE.COM
security = ads
idmap uid = 16777216-33554431
idmap gid = 16777216-33554431
idmap config RMOHAN:backend = rid
idmap config RMOHAN:range = 10000000-19999999
kerberos method = dedicated keytab
dedicated keytab file=/etc/krb5.keytab
template homedir = /home/%U
template shell = /bin/bash
winbind use default domain = true
winbind offline logon = false

6. Restart Winbind service
Once you have added your system to the domain, it is important to restart the Winbind service.

[root@server ~]# service winbind restart
Shutting down Winbind services:                            [FAILED]
Starting Winbind services:                                 [  OK  ]
[root@server ~]#

7. Create a Kerberos keytab to enable Single Sign On (SSO)

[root@server ~]# net ads keytab create -U Administrator
Enter Administrator’s password:
[root@server ~]#

8. Test configuration. If you receive no output for a known username, then something is wrong.

[root@server ~]# getent passwd Administrator
administrator:*:16777216:16777216:Administrator:/home/administrator:/bin/bash
[root@server ~]#

or, if you enabled shell logins,

User@workstation:~$ ssh Administrator@server.rmohan.com
Administrator@server.rmohan.com’s password:
Your password will expire in 11 days.

Creating home directory for administrator.
[administrator@server ~]$

9. This is optional, your home directory will not exist on the system when a new user logs in, run the below command if you with to have the homedir automatically created on first login.

[root@server ~]# authconfig –enablemkhomedir –update
Starting Winbind services:                                 [  OK  ]
Starting oddjobd:                                          [  OK  ]
[root@server ~]#

 

authconfig –enablemkhomedir –update

service messagebus restart

/etc/init.d/oddjobd restart

service winbind restart

 

 

Oddjobd fails to start [FIXED]