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<h1>RHEL 6.4 onwards</h1>
<h2>Install</h2>
<p>
Pacemaker ships as part of the Red
Hat <a href="http://www.redhat.com/products/enterprise-linux-add-ons/high-availability/">High
Availability Add-on</a>. The easiest way to try it out on RHEL is to install it from the <a href="http://scientificlinux.org">Scientific Linux</a> or <a href="http://www.centos.org">CentOS</a> repositories.
</p>
<p>
If you are already running CentOS or Scientific Linux, you can skip this step. Otherwise, to teach the machine where to find the CentOS packages, run:
</p>
<p class="command">
[ALL] # cat <<EOF > /etc/yum.repo.d/centos.repo
[centos-6-base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
enabled=1
EOF
</p>
<p>
Next we use yum to install pacemaker and some other
necessary packages we will need:
</p>
<p class="command">
[ALL] # yum install pacemaker cman pcs ccs resource-agents
</p>
<h2>Configure Cluster Membership and Messaging</h2>
<p>
The supported stack on RHEL6 is based on CMAN, so thats
what Pacemaker uses too.
</p>
<p>
We now create a CMAN cluster and populate it with some
nodes. Note that the name cannot exceed 15 characters
(we'll use 'pacemaker1').
</p>
<p class="command">
[ONE] # ccs -f /etc/cluster/cluster.conf --createcluster pacemaker1
[ONE] # ccs -f /etc/cluster/cluster.conf --addnode node1
[ONE] # ccs -f /etc/cluster/cluster.conf --addnode node2
</p>
<p>
Next we need to teach CMAN how to send it's fencing
requests to Pacemaker. We do this regardless of whether
or not fencing is enabled within Pacemaker.
</p>
<p class="command">
[ONE] # ccs -f /etc/cluster/cluster.conf --addfencedev pcmk agent=fence_pcmk
[ONE] # ccs -f /etc/cluster/cluster.conf --addmethod pcmk-redirect node1
[ONE] # ccs -f /etc/cluster/cluster.conf --addmethod pcmk-redirect node2
[ONE] # ccs -f /etc/cluster/cluster.conf --addfenceinst pcmk node1 pcmk-redirect port=node1
[ONE] # ccs -f /etc/cluster/cluster.conf --addfenceinst pcmk node2 pcmk-redirect port=node2
</p>
<p>
Now copy <strong>/etc/cluster/cluster.conf</strong> to all
the other nodes that will be part of the cluster.
</p>
<h2>Start the Cluster</h2>
<p>
CMAN was originally written for rgmanager and assumes the
cluster should not start until the node has
<a href="http://en.wikipedia.org/wiki/Quorum">quorum</a>,
so before we try to start the cluster, we need to disable
this behavior:
</p>
<p class="command">
[ALL] # echo "CMAN_QUORUM_TIMEOUT=0" >> /etc/sysconfig/cman
</p>
<p>
Now, on each machine, run:
</p>
<p class="command">
[ALL] # service cman start
[ALL] # service pacemaker start
</p>
<h2>A note for users of prior RHEL versions</h2>
<p>
The original cluster shell (crmsh)
is <a href="http://blog.clusterlabs.org/blog/2013/pacemaker-on-rhel6-dot-4/">no
longer available</a> on RHEL. To help people make the
transition there is
a <a href="https://github.com/ClusterLabs/pacemaker/blob/master/doc/pcs-crmsh-quick-ref.md">
quick reference guide</a> for those wanting to know what
the pcs equivalent is for various crmsh commands.
</p>
<h2>Set Cluster Options</h2>
<p>
With so many devices and possible topologies, it is nearly
impossible to include Fencing in a document like this.
For now we will disable it.
</p>
<p class="command">
[ONE] # pcs property set stonith-enabled=false
</p>
<p>
One of the most common ways to deploy Pacemaker is in a
2-node configuration. However quorum as a concept makes
no sense in this scenario (because you only have it when
more than half the nodes are available), so we'll disable
it too.
</p>
<p class="command">
[ONE] # pcs property set no-quorum-policy=ignore
</p>
<p>
For demonstration purposes, we will force the cluster to
move services after a single failure:
</p>
<p class="command">
[ONE] # pcs resource defaults migration-threshold=1
</p>
<h2>Add a Resource</h2>
<p>
Lets add a cluster service, we'll choose one doesn't
require any configuration and works everywhere to make
things easy. Here's the command:
</p>
<p class="command">
[ONE] # pcs resource create my_first_svc Dummy op monitor interval=120s
</p>
<p>
"<strong>my_first_svc</strong>" is the name the service
will be known as.
</p>
<p>
"<strong>ocf:pacemaker:Dummy</strong>" tells Pacemaker
which script to use
(<a href="https://github.com/ClusterLabs/pacemaker/blob/master/extra/resources/Dummy">Dummy</a>
- an agent that's useful as a template and for guides like
this one), which namespace it is in (pacemaker) and what
standard it conforms to
(<a href="/doc/en-US/Pacemaker/1.1-pcs/html/Pacemaker_Explained/s-resource-supported.html#_open_cluster_framework">OCF</a>).
</p>
<p>
"<strong>op monitor interval=120s</strong>" tells Pacemaker to
check the health of this service every 2 minutes by
calling the agent's <strong>monitor</strong> action.
</p>
<p>
You should now be able to see the service running using:
</p>
<p class="command">
[ONE] # pcs status
</p>
<p>
or
</p>
<p class="command">
[ONE] # crm_mon -1
</p>
<h2>Simulate a Service Failure</h2>
<p>
We can simulate an error by telling the service to stop
directly (without telling the cluster):
</p>
<p class="command">
[ONE] # crm_resource --resource my_first_svc --force-stop
</p>
<p>
If you now run <strong>crm_mon</strong> in interactive
mode (the default), you should see (within the monitor
interval - 2 minutes) the cluster notice
that <strong>my_first_svc</strong> failed and move it to
another node.
</p>
<h2>Next Steps</h2>
<p>
<ul>
<li>Configure <a href="/doc/en-US/Pacemaker/1.1-pcs/html/Clusters_from_Scratch/ch09.html">Fencing</a></li>
<li>Add more services - see <a href="/doc/en-US/Pacemaker/1.1-pcs/html/Clusters_from_Scratch/ch06.html">Clusters from Scratch</a> for examples of how to add IP address, Apache and DRBD to a cluster</li>
<li>Learn how to make services <a href="/doc/en-US/Pacemaker/1.1-pcs/html/Clusters_from_Scratch/_specifying_a_preferred_location.html">prefer a specific host</a></li>
<li>Learn how to make services <a href="/doc/en-US/Pacemaker/1.1-pcs/html/Clusters_from_Scratch/_ensuring_resources_run_on_the_same_host.html">run on the same host</a></li>
<li>Learn how to make services <a href="/doc/en-US/Pacemaker/1.1-pcs/html/Clusters_from_Scratch/_controlling_resource_start_stop_ordering.html">start and stop</a> in a specific order</li>
<li>Find out what else Pacemaker can do - see <a href="/doc/en-US/Pacemaker/1.1-pcs/html/Pacemaker_Explained/index.html">Pacemaker Explained</a> for an comprehensive list of concepts and options</li>
</ul>
</p>
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