Introduction to Pacemaker Cluster Tools (RHEL 8 and later)

Updated 31 Mar 2025

This article provides an introduction to creating a Pacemaker cluster. By working through this procedure, you will learn how to use Pacemaker to set up a cluster, how to display cluster status, and how to configure a cluster service. This example creates an Apache HTTP server as a cluster resource and shows how the cluster responds when the resource fails.

For an introduction to creating a Pacemaker cluster running a service that will fail over from one node to another when the node on which the service is running becomes unavailable, see Introduction to Failover in a Pacemaker Cluster (RHEL 8 and later).

Note: This procedure does not create a supported Red Hat cluster, which requires at least two nodes and the configuration of a fencing device. For full information about Red Hat’s support policies, requirements, and limitations for RHEL High Availability clusters, see This content is not included.Support Policies for RHEL High Availability Clusters.

In this example:

The node is z1.example.com.
The floating IP address is 192.168.122.120.

Prerequisites

A single node running RHEL 8 or later
A floating IP address that resides on the same network as one of the node’s statically assigned IP addresses
The name of the node on which you are running is in your /etc/hosts file

Procedure

Install the Red Hat High Availability Add-On software packages from the High Availability channel, and start and enable
the pcsd service.
```
 # dnf install pcs pacemaker fence-agents-all
 ...
 # systemctl start pcsd.service 
 # systemctl enable pcsd
```
If you are running the firewalld daemon, on both nodes enable the ports that are required by the Red Hat High Availability Add-On.
```
 # firewall-cmd --permanent --add-service=high-availability
 # firewall-cmd --reload
```
Set a password for user hacluster on each node in the cluster and authenticate user hacluster for each node in the cluster on the node from which you will be running the pcs commands. This example is using only a single node, the node from which you are running the commands, but this step is included here since it is a necessary step in configuring a supported Red Hat High Availability multi-node cluster.
```
 # passwd hacluster
 # pcs host auth z1.example.com 
```

Create a cluster named my_cluster with one member and check the status of the cluster. This command creates and starts the cluster in one step.

 # pcs cluster setup  my_cluster --start z1.example.com 
...
 # pcs cluster status
 Cluster Status:
   Stack: corosync
  Current DC: z1.example.com (version 2.0.0-10.el8-b67d8d0de9) - partition with quorum
  Last updated: Thu Oct 11 16:11:18 2018
  Last change: Thu Oct 11 16:11:00 2018 by hacluster via crmd on z1.example.com  
  1 node configured
  0 resources configured

 PCSD Status:
   z1.example.com: Online

A Red Hat High Availability cluster requires that you configure fencing for the cluster. The reasons for this requirement are described in the Red Hat Knowledgebase solution Fencing in a Red Hat High Availability Cluster. For this introduction, however, which is intended to show only how to use the basic Pacemaker commands, disable fencing by setting the stonith-enabled cluster option to false.

Warning: The use of stonith-enabled=false is completely inappropriate for a production cluster. It tells the cluster to simply pretend that failed nodes are safely fenced.

To disable fencing, run the following command:
```
 # pcs property set stonith-enabled=false
```
Configure a web browser on your system and create a web page to display a simple text message. If you are running the firewalld daemon, enable the ports that are required by httpd.

Note: Do not use systemctl enable to enable any services that will be managed by the cluster to start at system boot.
```
 # dnf install -y httpd wget
 ...
 # firewall-cmd --permanent --add-service=http
 # firewall-cmd --reload

 # cat <<-END >/var/www/html/index.html
  <html>
  <body>My Test Site - $(hostname)</body>
  </html>
 END
```
In order for the Apache resource agent to get the status of Apache, on each node in the cluster create the following addition to the existing configuration to enable the status server URL.
```
 # cat <<-END > /etc/httpd/conf.d/status.conf
 <Location /server-status>
 SetHandler server-status
 Order deny,allow
 Deny from all
 Allow from 127.0.0.1
 Allow from ::1
 </Location>
 END
```

Create IPaddr2 and apache resources for the cluster to manage. The IPaddr2 resource is a floating IP address that must not be one already associated with a physical node. If the IPaddr2 resource's NIC device is not specified, the floating IP must reside on the same network as the statically assigned IP address used by the node,

You can display a list of all available resource types with the pcs resource list command. You can use the pcs resource describe resourcetype command to display the parameters you can set for the specified resource type. For example, the following command displays the parameters you can set for a resource of type apache:

 # pcs resource describe apache
 ...

In this example, the IP address resource and the apache resource are both configured as part of a group named apachegroup, which ensures that the resources are kept together to run on the same node when you are configuring a working multi-node cluster.

 # pcs resource create ClusterIP ocf:heartbeat:IPaddr2 ip=192.168.122.120 --group apachegroup

 # pcs resource create WebSite ocf:heartbeat:apache configfile=/etc/httpd/conf/httpd.conf statusurl="http://localhost/server-status" --group apachegroup

 # pcs status
 Cluster name: my_cluster
 Stack: corosync
 Current DC: z1.example.com (version 2.0.0-10.el8-b67d8d0de9) - partition with quorum
 Last updated: Fri Oct 12 09:54:33 2018
 Last change: Fri Oct 12 09:54:30 2018 by root via cibadmin on z1.example.com

 1 node configured
 2 resources configured

 Online: [ z1.example.com ]

 Full list of resources:

 Resource Group: apachegroup
     ClusterIP  (ocf::heartbeat:IPaddr2):       Started z1.example.com
     WebSite    (ocf::heartbeat:apache):        Started z1.example.com

 PCSD Status:
   z1.example.com: Online

 After you have configured a cluster resource, you can use the pcs resource config command to display the options that are configured for that resource.

Point your browser to the website you created using the floating IP address you configured. This should display the text message you defined.

Stop the apache web service and check the cluster status. Using killall -9 simulates an application-level crash.

 # killall -9 httpd

 Check the cluster status. You should see that stopping the web service caused a failed action, but that the cluster software restarted the service and you should still be able to access the website. 

 # pcs status
 Cluster name: my_cluster
 ...
 Current DC: z1.example.com (version 1.1.13-10.el7-44eb2dd) - partition with quorum
 1 node and 2 resources configured

 Online: [ z1.example.com ]

 Full list of resources:

 Resource Group: apachegroup
     ClusterIP  (ocf::heartbeat:IPaddr2):       Started z1.example.com
     WebSite    (ocf::heartbeat:apache):        Started z1.example.com

 Failed Resource Actions:
 * WebSite_monitor_60000 on z1.example.com 'not running' (7): call=13, status=complete, exitreason='none',
         last-rc-change='Thu Oct 11 23:45:50 2016', queued=0ms, exec=0ms

 PCSD Status:
     z1.example.com: Online

You can clear the failure status on the resource that failed once the service is up and running again and the failed action notice will no longer appear when you view the cluster status.

 # pcs resource cleanup WebSite

When you are finished looking at the cluster and the cluster status, stop the cluster services on the node. Even though you have only started services on one node for this introduction, the --all parameter is included since it would stop cluster services on all nodes on an actual multi-node cluster.
```
 # pcs cluster stop --all
```

Article Type

General