A Complete Beginner’s Guide to Managing a Pacemaker Cluster

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A Beginner’s Guide to Managing a Pacemaker Cluster

Pacemaker is a powerful tool for managing highly available Linux clusters. It helps ensure that critical applications and services stay online, even if one or more nodes fail. In this article, we’ll explore some of the basic commands and concepts of managing a Pacemaker cluster. If you’ve never set up a cluster before then you may wish to read “Step-by-Step Guide: Setting Up a High-Availability Cluster for Nginx, PHP-FPM, and MySQL with Pacemaker and DRBD” before continuing.

Pacemaker Commands for Managing Resources

One of the most important aspects of managing a Pacemaker cluster is managing the resources that the cluster is responsible for. Some useful commands for managing resources include:

• pcs resource cleanup: This command cleans up resources that have failed or have been moved to another node.
• pcs resource create: This command creates a new resource in the cluster, such as a virtual IP address or a file system.
• pcs resource delete: This command deletes a resource from the cluster.
• pcs resource move: This command moves a resource from one node to another.

Pacemaker Commands for Checking the Status of the Cluster

Another important aspect of managing a Pacemaker cluster is checking the status of the cluster and its resources. Some useful commands for checking the status of the cluster include:

• pcs status: This command shows the current status of the cluster, including which nodes are active, which resources are running, and any issues that have been detected.
• crm_mon: This command shows a real-time view of the cluster, including node status, resource status, and any alerts or warnings.

Managing Standby Nodes and Data Synchronization

Another important aspect of managing a Pacemaker cluster is managing standby nodes and data synchronization. Standby nodes are nodes that are not currently running resources but are available to take over if another node fails. Some useful commands for managing standby nodes include:

• pcs node standby: This command puts a node into standby mode, which means that it will not run any resources but is available to take over if another node fails.
• pcs node unstandby: This command takes a node out of standby mode and makes it available to run resources.

In addition to managing standby nodes, Pacemaker also provides several mechanisms for synchronizing data across the cluster. These include:

• DRBD (Distributed Replicated Block Device): A network block device that provides synchronized data replication across nodes.
• NFS (Network File System): A file system that allows multiple nodes to share the same data over a network.

Conclusion

Pacemaker is a powerful tool for managing highly available Linux clusters. By using the commands and concepts described in this article, you can gain a better understanding of how Pacemaker works and how to manage a Pacemaker cluster effectively.

Here are a few external resources you can check out for more information on Pacemaker:

• The Pacemaker documentation
• The Pacemaker GitHub repository

Keywords: Pacemaker, cluster resource manager, highly available, resource agents, resource groups, DRBD, NFS, GFS2.

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