Samba CTDB GPFS Cluster HowTo

From SambaWiki
Jump to: navigation, search

Creating a Samba Cluster with CTDB and GPFS on CENTOS

Want to build a scalable networked storage system that is always available ?, A system that integrates with your Active Directory, supports SMB2 protocol and ACL's. Then read on...

Assumed knowledge

This guide is written to assist a relatively inexperienced users through the setup of a fairly complex system in a step by step fashion. However, for the sake brevity I'm going to assume you are reasonably comfortable with GNU\Linux, can use Vim, Emacs or Nano. Have a grasp of basic networking etc.. and are not afraid of compiling some code :) . Elements of this setup are somewhat interchangeable. You could probably replace CENTOS with another distro but would subsequently need to be familiar enough with that distro to be able to modify the appropriate commands and paths. Others may wish to replace GPFS with alternate clustered file system or use a variation of my Samba configuration below. This setup has been tested in a non production environment. Deploying as such in a production environment is at your own risk and the author as such assumes no responsibility .

Preparing the Servers

This is a simple test setup. I’m going to use a couple of KVM VM’s but the same principles should apply on bare metal . This approach should scale to many physical/virtual servers . The diagram below illustrates our setup.


Install CENTOS 6.

First we want to install a couple of servers. I have chosen CENTOS 6 as it is binary compatible with RHEL 6 which is well supported by both GPFS and Samba. Create a couple of CENTOS 6 VM’s (I use virt-manager on CENTOS 6 but you can use any tools you like) . I use an ISO image CentOS-6.4-x86_64-minimal.iso. The VM will have 1 CPU and 1G RAM and an 8Gig disk . Initially I allocate 1 NIC but we will add a further NIC for a private LAN later.

Select all the usual defaults. Select the option to manually configure networking as we are going to configure this after install. Also make sure you install the SSH server. Once the servers are installed we need to set the IP address. You can do this by editing /etc/sysconfig/network-scripts/ifcfg-eth0 file and setting static IP addresses .These are the publicly accessible IP addresses of the servers. For reference here is the ifcfig-eth0 file on the sambagpfs1 server :


Don’t forget to set a valid DNS server in /etc/resolv.conf also. Once you're sure you have a working network connection, install the latest updates with the yum update command.

Configure shared disks

In virt-manager create a couple of 1GB IDE disks for our GPFS Cluster. When you try to add the disk to the 2nd server (sambagpfs2) virt-manager will give you a warning that “the disk is already in use by another guest” but this is OK. We are building a clustered file system where shared access to the underlying disks is necessary.

In a production scenario these disks would usually be shared LUN’s on a SAN. When you reboot your servers you should see the additional disks as reported by the dmesg command. You should see something like :

sd 0:0:0:0: [sda] 2048000 512-byte logical blocks: (1.04 GB/1000 MiB)
sd 0:0:1:0: [sdb] 2048000 512-byte logical blocks: (1.04 GB/1000 MiB)

Make sure you can see both disks from both servers (sambagpfs1 and sambagpfs2).

Disable SELINUX and iptables

There appears to be a communication problem between the GPFS Daemons when SELINUX is enabled. Edit the /etc/selinux/config file and set SELINUX=disabled. Also stop the iptables server and disable it on restart.

service iptables stop
chkconfig iptables off

It goes without saying that you need to consider these steps more carefully in a production environment.

Create an addition network card and set up password less login

Create an additional network card in virt-manager for each of our guests. These NIC’s are for communication (GPFS and CTDB Stuff) between the guests so we place them on the Virtual network ‘default’ NAT. Give the NIC’s sensible addresses, something like 192.168.1.x .. Create a file /etc/sysconfig/network-scripts/ifcfg-eth1 for the new network interface . Sample config below :


Generate the ssh key with the ssh-keygen -t rsa command on sambagpfs1 and copy to the other server using the command ssh-copy-id -i /root/.ssh/ .

Also in the ~/.ssh folder run cat >> authorized_keys . This is necessary as our GPFS setup uses the ssh shell to execute commands locally as well as remotely. Otherwise we will be prompted for a login on the local machine when executing GPFS commands .

Now, perform the inverse of the above on the second server gpfstest2. You should now be able to zip between the two servers with the ssh <IP address> command. If not use the -v switch in the ssh command to debug.

Hostnames in hosts file

Add your hostnames and internal IP addresses to the /etc/hosts file . My settings displayed below for reference.     sambagpfs1     sambagpfs2    smbgpfscluster    smbgpfscluster

Keep time synchronised

Install the ntp service :

yum install ntp

Set your local ntp server in /etc/ntp.conf . Set service to start on boot :

chkconfig ntpd on

and start the service :

service ntpd start

Check the time is synchronised using the date command.

Now we are just about ready to begin installing GPFS :) .

Install and configure GPFS

Important !. Ensure you have the appropriate licensing before installing GPFS. For more information see

Copy the appropriate GPFS related rpm’s onto your servers. You must install the base GPFS rpm’s and then install the patch rpm’s

Machine 1 - sambagpfs1

First of all we need to install some dependencies necessary to install GPFS and build the portability layer rpm :

yum install perl rsh ksh compat-libstdc++-33 make kernel-devel gcc gcc-c++ rpm-build

Now, install the GPFS base rpms :

rpm -ivh gpfs.*0-0*

then the patch rpm’s :

rpm -Uvh gpfs.*0-14*.rpm

Build the Portability layer :

yum install


make World

make rpm (Note it’s not best practice to build rpm as root)

This will build an rpm for the portability layer . The benefit of building this rpm is that we will not need as many prerequisites in our other cluster members.

Install the portability rpm.

rpm -Uvh /root/rpmbuild/RPMS/x86_64/gpfs.gplbin-2.6.32-358.18.1.el6.x86_64-3.4.0-14.x86_64.rpm

In general it is bad practice to build as root. See . As this is a non production test system i’m going to give myself a pass (for the moment).

Finally, copy the portability rpm to the other cluster servers, in this case sambagpfs2 .

Machine 2 - sambagpfs2

Install some dependencies :

yum install perl rsh ksh compat-libstdc++-33

the base rpm’s :

rpm -ivh gpfs.*0-0*

the patch rpm’s :

rpm -Uvh gpfs.*0-14*.rpm

Install the portability RPM.

rpm -Uvh gpfs.gplbin-2.6.32-358.18.1.el6.x86_64-3.4.0-14.x86_64.rpm

Update your path to include the GPFS administration commands

Add the GPFS commands to the path (you don’t strictly need to do this but it makes administration of GPFS more convenient !). Edit you .bash_profile and set the path to something like :


and run source .bash_profile to update your path

Creating the GPFS Cluster

Create a file gpfsnodes.txt containing information about our GPFS cluster nodes


Create the test cluster using the mmcrcluster command.

mmcrcluster -N gpfsnodes.txt -p sambagpfs1 -s sambagpfs2 -r /usr/bin/ssh -R /usr/bin/scp -C SAMBAGPFS -A

This sets sambagpfs1 as the primary server and sambagpfs2 as the secondary server. -A specifies that the GPFS daemons start on boot.

Accept the license for you servers :

mmchlicense server --accept -N sambagpfs1

mmchlicense server --accept -N sambagpfs2

Use the mmlscluster command to verify that the cluster has been created correctly.

Now create our NSD’s for our two shared disks /dev/sda and /dev/sdb.

Firstly create two files, nsd.txt :


and nsd2.txt


Now issue the command :

mmcrnsd -F nsd.txt


mmcrnsd -F nsd2.txt

Use the mmlsnsd command to verify creation.

Start up the cluster :

mmstartup -a

Check the cluster is up with mmgetstate -a

Create the GPFS file system :

mmcrfs /dev/sambagpfs -F nsd.txt -A yes -B 256K -n 2 -M 2 -r1 -R2 -T /sambagpfs

Add the second disk to the filesystem :

mmadddisk sambagpfs -F nsd2.txt

Use the mmlsnsd to verify that the two disk have been added to the cluster file system . You should see something similar to the following :

File system   Disk name    NSD servers
sambagpfs     test01       sambagpfs1,sambagpfs2
sambagpfs     test02       sambagpfs2,sambagpfs1

We only have 2 nods in our GPFS Cluster so we need to set a tie breaker disk . Shut down GPFS to add the tie breaker disk.

mmshutdown -a

mmchconfig tiebreakerdisks=test01

To ensure recent versions of Microsoft Excel work correctly over SMB2 we also need to set the following configuration in GPFS (Many thanks to Dan Cohen at IBM - XIV for this tip).

mmchconfig cifsBypassShareLocksOnRename=yes -i

Start up our GPFS Cluster again :

mmstartup -a

Mount the GPFS filesystem :

mmmount sambagpfs -a

At this point you should see the GPFS file system mounted at /sambagpfs on both of our servers. Congratulations !. Take a break, stand up and walk around for a bit.

Install and Configure Samba and CTDB

I use the SerNet Samba 4 RPM’s from . You have to register at the site (free) to download the RPM’s. There appears to be a problem with Windows 7 (which uses SMB2 if available on the server) on the latest release 4.0.10 so I am currently using the 4.0.9 release . I have yet to test with 4.1. Once you register you can find the 4.0.9 rpm’s at

You need to download the following rpm’s :


First we need to install a couple of dependencies :

yum install redhat-lsb-core cups-libs

Then install the samba packages :

rpm -Uvh sernet-samba-*

We want to control samba from CTDB so stop the samba daemons from starting on boot on our servers :

chkconfig sernet-samba-nmbd off chkconfig sernet-samba-smbd off chkconfig sernet-samba-smbd off

Install and configure CTDB

Download the latest CTDB sources (2.4 at time of writing) onto the sambagpfs1 server from . Extract the tar.gz to the gpfs file system /sambagpfs and on the sambagpfs1 server run

yum install autoconf




make install

Now run make install on the sambagpfs2 also.

Create /etc/sysconfig/ctdb with the following contents


Next create the directory /usr/local/var

mkdir /usr/local/var

Then change directory to /usr/local/etc/ctdb/ and create the following files containing the following data


public_addresses eth0 eth0

Also create a shared recovery file :

touch /sambagpfs/recovery.lck

Configuring Samba

Edit the /etc/default/sernet-samba file and set the following parameter :


Now we need to create our smb.conf in /etc/samba. I have copied the contents of my smb.conf file below for reference :

#===== Global Settings ============
netbios name = smbgpfscluster
server string = Samba Version %v on $h
workgroup = HOHO
security = ADS

# These were useful for debugging my initial setup but are probably too verbose for general use
log level = 3 passdb:3 auth:3 winbind:10 idmap:10
idmap config *:backend = tdb2
idmap config *:range = 1000-90000
winbind use default domain = yes

# Set these to no as it doesn't  work well when you have thousands of users in your domain
winbind enum users  = no
winbind enum groups =  no
winbind cache time = 900
winbind normalize names = no

clustering = yes
unix extensions = no
mangled names = no
ea support = yes
store dos attributes = yes
map readonly = no
map archive = no
map system = no
force unknown acl user = yes

# Stuff necessary for guest logins to work where required
guest account = nobody
map to guest = bad user

#============ Share Definitions ============
comment = GPFS Cluster on %h using %R protocol
path = /sambagpfs
writeable = yes
create mask = 0770
force create mode = 0770
locking = yes
vfs objects = gpfs fileid

# vfs_gpfs settings
gpfs:sharemodes = yes
gpfs:winattr = yes
nfs4:mode = special
nfs4:chown = yes
nfs4:acedup = merge 

#some vfs related to clustering
fileid:algorithm = fsname

Notes on Samba config

This is a configuration for a AD domain member server. I did not have the necessary privileges on our AD to install RFC2307/SFU schema extensions . If you have such access then this would be a better way to proceed as you would have consistent UID/GID allocation between clusters.

Edit /etc/nsswitch.conf

passwd:     files winbind
shadow:     files
group:      files winbind

In /etc/krb5.conf file set your default realm

default_realm = HOHO.BALE.COM

Now start the CTDB daemon on both servers.

ctdbd --syslog --debug=3

run ctdb status

At this stage the nodes will report as unhealthy as winbind will not start as we have not joined the domain. So lets join the domain.

net ads join -U <some account with the necessary privileges> -d5

All going well you have successfully joined the domain if not the debug information will assist you in finding the issue.

winbind will not have started successfully when we first started CTDB so we can start it manually now.

service sernet-samba-winbindd start

Check the winbind daemon has started :

wbinfo -p

and verify you have successfully joined the domain :

wbinfo -t

and can authenticate a user against the domain :

wbinfo -a <avaliddomainusername>

In addition the following command should return valid user information.

id <vaildomainusername>

The wbinfo -u command should list the users on your domain . Our domain has 10’s of thousands of users so this may take some time. You may even have to to run run wbinfo a couple of times to get valid results.

The ctdb ip command should report the current assignment of our cluster ip’s .

Now try to access the shares from windows. For some reason that I could not fathom I was getting an access denied when I tried to access that shares at this point. I rebooted both servers and this appeared to resolve the issue :).


The only really tested GPFS ACLs style is -k nfsv4.

Configure your DNS Server

You need to create a DNS alias that redirects requests to your samba cluster in a round robin fashion. So in our setup we need to create an alias the resolves to both and .

Closing notes

So there you have it. I hope this guide has been useful. Any constructive feedback is welcome to improve the guide, particularly from anybody who is running such a system in a production enviornment.

For a complete open source solution you could replace GPFS for GlusterFS (which appears to be maturing nicely) or possibly OCFS2. Perhaps i will have time to test this some day but thats another days work.