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Chapter 2. Configuration Basics

Table of Contents

2.1. Configuration Layout
2.2. The Current State of the Cluster
2.3. How Should the Configuration be Updated?
2.4. Quickly Deleting Part of the Configuration
2.5. Updating the Configuration Without Using XML
2.6. Making Configuration Changes in a Sandbox
2.7. Testing Your Configuration Changes
2.8. Do I Need to Update the Configuration on all Cluster Nodes?

2.1. Configuration Layout

The cluster is written using XML notation and divided into two main sections; configuration and status.
The status section contains the history of each resource on each node and based on this data, the cluster can construct the complete current state of the cluster. The authoritative source for the status section is the local resource manager (lrmd) process on each cluster node and the cluster will occasionally repopulate the entire section. For this reason it is never written to disk and admin's are advised against modifying it in any way.
The configuration section contains the more traditional information like cluster options, lists of resources and indications of where they should be placed. The configuration section is the primary focus of this document.
The configuration section itself is divided into four parts:
  • Configuration options (called crm_config)
  • Nodes
  • Resources
  • Resource relationships (called constraints)
Example 2.1. An empty configuration

  <cib generated="true" admin_epoch="0" epoch="0" num_updates="0" have-quorum="false">