Tuesday, November 3, 2015

Joining CentOS/RHEL (6.x) to Active Directory (Windows Server Domain) [Updated]

***CASE MATTERS FOR EVERYTHING POSTED BELOW***

Install the following packages

yum install pam_krb5 pam_ldap nss-pam-ldapd samba ntp

*If you already have any of these installed, it'll skip them.

First make a backup of the config.
cp /etc/krb5.conf /etc/krb5.conf.bak

</etc/krb5.conf>
[logging]
 default = FILE:/var/log/krb5libs.log
 kdc = FILE:/var/log/krb5kdc.log
 admin_server = FILE:/var/log/kadmind.log

[libdefaults]
 default_realm = DOMAIN.COM
 dns_lookup_realm = false
 dns_lookup_kdc = false
 ticket_lifetime = 24h
 renew_lifetime = 7d
 forwardable = true

[realms]
 DOMAIN.COM = {
  kdc = DC.DOMAIN.COM
  admin_server = DC.DOMAIN.COM
  kdc = x.x.x.x
 }

[domain_realm]
 .domain.com = DOMAIN.COM
 domain.com = DOMAIN.COM

Again backup the config
cp /etc/samba/smb.conf /etc/samba/smb.conf.bak

You can also use system-config-authentication if you have a gui.

</etc/samba/smb.conf>
Note:  The workgroup is the left most part of the domain
[global]

workgroup = DOMAIN
password server = x.x.x.x
realm = DOMAIN.COM
security = ADS
winbind enum users = Yes
winbind enum groups = Yes
winbind use default domain = No
winbind separator = +
idmap config * : backend = autorid
idmap config * : range = 1000000-19999999
idmap config * : rngesize = 1000000
template homedir= /home/%D/%U
template shell = /bin/bash


*Note*
If you don't want the users to have to type DOMAIN+username then remove the winbind separator line and change the winbind user default domain = yes.  Restart smb and winbind.

Again backup the config
cp /etc/nsswitch.conf /etc/nsswitch.conf.bak

</etc/nsswitch.conf>
passwd:     files winbind
group:      files winbind
shadow:     files winbind

Again backup the config
cp /etc/ntp.conf /etc/ntp.conf.bak

</etc/ntp.conf>
Note:  The 1.1.1.1 is the ip of your server
server 1.1.1.1 

Pick one of these ways:
1. authconfig-tui (select Winbind, click ok. Select Use Shadow Passwords, Use Winbind Authentication, Local authorization is sufficient)

2. Create the files manually.

Again backup the config
cp /etc/pam.d/system-auth /etc/pam.d/system-auth.bak

</etc/pam.d/system-auth>
auth        required      pam_env.so
auth        sufficient    pam_unix.so try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        sufficient    pam_sss.so use_first_pass
auth        sufficient    pam_winbind.so use_first_pass
auth        required      pam_deny.so

account     required      pam_access.so
account     required      pam_unix.so broken_shadow
account     sufficient    pam_localuser.so
account     sufficient    pam_succeed_if.so uid < 500 quiet
account     [default=bad success=ok user_unknown=ignore] pam_sss.so
account     [default=bad success=ok user_unknown=ignore] pam_winbind.so
account     required      pam_permit.so

password    requisite     pam_cracklib.so difok=4 dcredit=-2 ucredit=-2 ocredit=-2 lcredit=-2 minlen=12 retry=3
password    sufficient    pam_unix.so sha512 shadow try_first_pass use_authtok
password    sufficient    pam_sss.so use_authtok
password    sufficient    pam_winbind.so use_authtok
password    required      pam_deny.so

session     optional      pam_keyinit.so revoke
session     required      pam_limits.so
session     optional      pam_oddjob_mkhomedir.so skel=/etc/skel umask=0644
session     [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid
session     required      pam_unix.so
session     optional      pam_sss.so


</etc/pam.d/sshd>
auth       required     pam_sepermit.so
auth       include      password-auth
auth    sufficient      pam_winbind.so
account    required     pam_nologin.so
account    include      password-auth
password   include      password-auth
# pam_selinux.so close should be the first session rule
session    required     pam_selinux.so close
session    required     pam_loginuid.so
# pam_selinux.so open should only be followed by sessions to be executed in the user context
session    required     pam_selinux.so open env_params
session    optional     pam_keyinit.so force revoke
session    include      password-auth

Edit your /etc/hosts file
</etc/hosts>
1.1.1.1 dc.server.centos.com dc


Restart the following services:

service smb restart
service winbind restart
service sshd restart
service ntpd restart
chkconfig winbind on

*If any of those fail, you have something configured wrong.
Then run:  [root@node001user1]# kinit domainadmin@CENTOS.COM (THIS MUST BE IN ALL CAPS!)

Confirm the ticket was obtained: [root@node001 user1]# klist

Get the time from the server: [root@node001 user1]# net time

Sync the time from the server: [root@node001 user1]# ntpdate -u

Then run the following command to join it to the domain.

[root@node001 user1]# net ads join -U domainadmin (replace with your domain admin username)

Run some more tests:

wbinfo -t
wbinfo -u
wbinfo -g

getent passwd
getent groups

If any of those fail, something isn't configured correctly.

If you want the domain admins and admins to have privileged access, you need to add this to the bottom of your sudoers file.  You may have to over write the read only file to save it.

</etc/sudoers> ***NEED TO VERIFY IF THIS STILL WORKS****
[root@node001 user1]# cat /etc/sudoers

%BUILTIN\administrators ALL=(ALL) ALL
%"domain admins" ALL=(ALL) ALL

Some great additional trouble shooting commands can be found here -> Link

Also if you need to find your base dn to locate the group your user accounts are stored, I explain how to do that here -> Link

Another Great reference is here:  Link

If you have a Red Hat Subscription, they provide some good additional information:  Link

Integrating Red Hat Enterprise Linux 6 with Active Directory (Last updated 2014): Link

Link

Tested: RHEL 6.4+Windows 2k8 R2, RHEL 6.4+Windows 2k12 R2

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