How To Set Up And Integrate An Ubuntu 10.04 LTSPv5 Server Into A Windows 2008 Active Directory Domain

Introduction

With the current economic conditions, companies have been trying to do more with less by recycling old hardware and utilizing open source software. That's also true where I work. Between our call center, finance, distribution, warehouse, and sales departments over 50% of the company's employees are running on RHEL4 LTSP thin clients. Recently it was decided to update our LTSP environment from RHEL4 to Ubuntu 10.04 with LTSPv5. Using the following steps, I was able to setup and integrate an Ubuntu 10.04 LTSPv5 server into a Windows 2008 Active Directory domain.

 

Assumptions

It is assumed that you have a Windows 2008 Active Directory Domain setup and working properly along with a DHCP server. Your domain controller can be your DHCP server or you can setup a different box to distribute the DHCP leases. If your domain controller or DHCP server are not setup, please set these up first. It is also assumed that the reader has some basic Linux experience. You will need to know how to move around in the Linux terminal, install applications, and edit files using vi or nano.

 

Hardware

Ubuntu LTSP Server

Dell PowerEdge 2650
2 Dual Core Intel(R) Xeon(TM) CPU 1.80GHz CPU's
8 GB RAM
3 73 GB SCSI U320 10K Hard drives in RAID 5 configuration
Dual power supply

Thin Clients

Dell Optiplex GX260
1 GB RAM
On-board video
No HD

Network Layout

For the purpose of this tutorial, this is the layout of the domain.internal network on the 10.0.0.0/24 subnet.

Network Layout

dc.domain.internal

Windows 2008 Server running Active Directory and DNS

server.domain.internal

Windows 2003 Server hosting user home directories and file shares

thinserver.domain.internal

Ubuntu 10.04.2 server with LTSPv5

dhcp.domain.internal

CentOS 5.0 server running dhcpd

 

Ubuntu LTSP Installation

To install Ubuntu with LTSP, follow the instructions here.

If your server has more than 4 GB of RAM, make sure you install the Linux PAE Kernel.

sudo apt-get install linux-generic-pae linux-headers-generic-pae

 

Add thinserver to the Windows Domain

Before we add thinserver to the domain, we're going to have to install Samba along with some other packages.

sudo apt-get install samba smbclient winbind libpam-cracklib krb5-user

Make sure that thinserver is named correctly.

hostname

If the hostname command doesn't return thinserver.domain.internal, rename it to thinserver.domain.internal.

hostname thinserver.domain.internal

Edit the /etc/resolv.conf to use dc.domain.internal as the primary DNS server.

search domain.internal
nameserver 10.0.0.10

On your domain controller create a host (A) record in your DNS for thinserver.

Verify that thinserver can resolve domain.internal:

nslookup domain.internal

The results should look something like this:

test@thinserver:~$ nslookup domain.internal
Server:        10.0.0.10
Address:    10.0.0.10

Name:    domain.internal
Address: 10.0.0.10

Make sure that Samba and Winbind are not running:

/etc/init.d/smbd stop
/etc/init.d/winbind stop

Just to be safe lets backup the smb.conf, krb5.conf, and PAM common files. I like to append the date when I make a backup of a file so that I know when the changes were made.

d=`date "+%m%d%y"`
cp /etc/samba/smb.conf{,.$d}
cp /etc/krb5.conf{,.$d}
mkdir /etc/pam.d/backup
cd /etc/pam.d/
for file in `ls`;do cp $file{,.$d}; done
mv *.$d backup/

Edit the /etc/krb5.conf file to look like this:

[logging]
 default = FILE:/var/log/krb5libs.log
 kdc = FILE:/var/log/krb5kdc.log
 admin_server = FILE:/var/log/kadmind.log

[libdefaults]
 default_realm = DOMAIN.INTERNAL
 default_keytab_name = FILE:/etc/krb5.keytab
 default_tgs_entypes = rc4-hmac des-cbc-md5
 default_tkt_entypes = rc4-hmac des-cbc-md5
 permitted_entypes = rc4-hmac des-cbc-md5
 dns_lookup_realm = true
 dns_lookup_kdc = true
 ticket_lifetime = 24h
 forwardable = yes

[realms]

 DOMAIN.INTERNAL = {
  kdc = DC.DOMAIN.INTERNAL:88
  default_domain = DOMAIN.INTERNAL 
 }

[domain_realm]

 domain.internal = DOMAIN.INTERNAL
 .domain.internal = DOMAIN.INTERNAL
[appdefaults]
 forwardable = true
 pam = {
   minimum_uid = 16777216
   debug = false
   ticket_lifetime = 36000
   renew_lifetime = 36000
   krb4_convert = false
   DOMAIN.INTERNAL = {
	ignore_k5login = true
	}
 }

Edit the /etc/samba/smb.conf file to look like this:

[global]
   workgroup = DOMAIN
   password server = *
   realm = DOMAIN.INTERNAL
   local master = no
   security = ads
   idmap backend = tdb
   idmap uid = 16777216-33554431
   idmap gid = 16777216-33554431
   idmap config DOMAIN : backend = rid
   idmap config DOMAIN : range = 16777216-33554431
   idmap cache time = 60	
   template homedir = /home/%u
   template shell = /bin/bash
   kerberos method = secrets and keytab
   dedicated keytab file = /etc/krb5.keytab
   winbind separator = +
   winbind use default domain = yes
   winbind refresh tickets = true
   winbind cache time = 10
   winbind offline logon = true
   winbind enum users = Yes
   winbind enum groups = Yes
   passdb backend = tdbsam

   server string = Samba Server Version %v
   log file = /var/log/samba/%m.log
   max log size = 50

Moving forward it's advisable to have a second root terminal open just in case something doesn't work as expected. Happens to the best of us :o)

I would recommend creating a "linux_admins" group in Active Directory and adding it to the /etc/sudoers file. An alternative is to add the "domain admins" group and to login using the administrator account.

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL
%linux_admins ALL=(ALL) ALL

Edit the PAM common file /etc/pam.d/common-account:

account     sufficient	  pam_winbind.so use_first_pass cached_login 
account     required      pam_unix.so broken_shadow

Edit the PAM common file /etc/pam.d/common-auth:

auth	[success=2 default=ignore]	pam_unix.so nullok_secure
auth	[success=1 default=ignore]	pam_winbind.so krb5_auth krb5_ccache_type=FILE cached_login try_first_pass
auth	requisite			pam_deny.so
auth	required			pam_permit.so

Edit the PAM common file /etc/pam.d/common-password:

password	requisite			pam_cracklib.so retry=3 minlen=8 difok=3
password	[success=2 default=ignore]	pam_unix.so obscure use_authtok try_first_pass sha512
password	[success=1 default=ignore]	pam_winbind.so use_authtok try_first_pass
password	requisite			pam_deny.so
password	required			pam_permit.so
password	optional			pam_gnome_keyring.so

Edit the PAM common file /etc/pam.d/common-session:

session	    required	  		pam_env.so
session     required      		pam_unix.so
session     required      		pam_winbind.so use_first_pass 
session     required      		pam_limits.so
session     required      		pam_mkhomedir.so
session     [success=1 default=ignore] 	pam_succeed_if.so service in crond quiet use_uid

Edit the PAM common file /etc/pam.d/common-session-noninteractive:

session		[default=1]		pam_permit.so
session		requisite		pam_deny.so
session		required		pam_permit.so
session		optional		pam_winbind.so cached_login
session		required		pam_unix.so

Make sure that /etc/nsswitch.conf has the winbind entries for login.

passwd:         compat winbind
group:          compat winbind
shadow:         compat

Now we're ready to add thinserver to the Windows Domain.

kinit [email protected]
net ads join -U administrator
net ads keytab create -U administrator
/etc/init.d/smbd start
/etc/init.d/winbind start

Verify that you are on the domain and that you can see all the users and groups in the domain.

wbinfo -u
wbinfo -g
getent passwd

You should now be able to log onto the server with your domain username and password. Verify that you're getting a Kerberos ticket.

klist
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