Installation guide

specialized services to clients. An HA service is represented as a resource tree in the cluster
configuration file, /etc/cl uster/cluster. co nf (in each cluster node). In the cluster
configuration file, each resource tree is an XML representation that specifies each resource, its
attributes, and its relationship among other resources in the resource tree (parent, child, and sibling
relationships).
Note
Because an HA service consists of resources organized into a hierarchical tree, a service is
sometimes referred to as a resource tree or resource group. Both phrases are synonymous with
HA service.
At the root of each resource tree is a special type of resource — a service resource. Other types of
resources comprise the rest of a service, determining its characteristics. Configuring an HA service
consists of creating a service resource, creating subordinate cluster resources, and organizing them
into a coherent entity that conforms to hierarchical restrictions of the service.
There are two major considerations to take into account when configuring an HA service:
The types of resources needed to create a service
Parent, child, and sibling relationships among resources
The types of resources and the hierarchy of resources depend on the type of service you are
configuring.
The types of cluster resources are listed in Appendix B, HA Resource Parameters. Information about
parent, child, and sibling relationships among resources is described in Appendix C, HA Resource
Behavior.
2.7. Configurat ion Validat ion
The cluster configuration is automatically validated according to the cluster schema at
/usr/share/cluster/cl uster.rng during startup time and when a configuration is reloaded.
Also, you can validate a cluster configuration any time by using the ccs_co nfi g _vali d ate
command. For information on configuration validation when using the ccs command, see
Section 5.1.6, “ Configuration Validation” .
An annotated schema is available for viewing at /usr/share/d o c/cman-
X. Y . ZZ/cluster_conf. html (for example /usr/share/do c/cman-
3. 0 . 12/cluster_conf. html ).
Configuration validation checks for the following basic errors:
XML validity — Checks that the configuration file is a valid XML file.
Configuration options — Checks to make sure that options (XML elements and attributes) are
valid.
Option values — Checks that the options contain valid data (limited).
The following examples show a valid configuration and invalid configurations that illustrate the
validation checks:
Valid configuration — Example 2.3, “ cl uster. co nf Sample Configuration: Valid File”
⁠Chapt er 2 . Before Configuring t he Red Hat High Availabilit y Add- O n
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