System Definition

Each system designated as part of the cluster is listed in this section of main.cf. The names listed as system names must match the name returned by the command uname -a.
System names are preceded with the keyword "system." For any system to be used in a service group definition, it must be defined in this section. Each service group can be configured to run on a subset of systems defined in this section.

Service Group Definition

Service group definitions in main.cf comprise the attributes of a particular service group. See Service Group Attributes for a complete list. The following information describes two common service group attributes: SystemList and AutoStartList.

SystemList Attribute

The SystemList attribute designates all systems on which a service group can come online. By default, the order of systems in the list defines the priority of systems used in a failover. For example, the definition SystemList = { SystemA, SystemB, SystemC } configures SystemA to be the first choice on failover, followed by SystemB and then SystemC.

System priority may also be assigned explicitly in the SystemList attribute by assigning numeric values to each system name. For example: SystemList = { SystemA=0, SystemB=1, SystemC=2 }

If you assign numeric priority values, VCS assigns a priority to the system without a number by adding 1 to the priority of the preceding system. For example, if the SystemList is defined as SystemList = { SystemA, SystemB=2, SystemC }, VCS assigns the values SystemA = 0, SystemB = 2, SystemC = 3.

Note that a duplicate numeric priority value may be assigned when the following occurs:

SystemList = { SystemA, SystemB=0, SystemC }

The numeric values assigned are SystemA = 0, SystemB = 0, SystemC = 1.

To avoid the same priority number being assigned to more than one system, do not assign any numbers or assign different numbers to each system in SystemList.

AutoStartList Attribute

List of systems on which the service group will be started with VCS (usually at system boot). For example, if a system is a member of a failover service group's AutoStartList attribute, and if the service group is not already running on another system in the cluster, the group is brought online when the system is started.

Resource Definition

This section in main.cf defines each resource used in a particular service group. Resources can be added in any order and the utility hacf arranges the resources alphabetically the first time the configuration file is run.

Service Group Dependency Clause

To configure a service group dependency, place the keyword "requires" in the service group declaration of the main.cf file. Position the dependency clause before the resource dependency specifications and after the resource declarations.

Resource Dependency Clause

A dependency between resources is indicated by the keyword "requires" between two resource names. This indicates the second resource (the child) must be online before the first resource (the parent) can be brought online. Conversely, the parent must be offline before the child can be taken offline. Also, faults of the children are propagated to the parent.

Example 1: Initial Configuration

When VCS is installed, a basic main.cf configuration file is created with the cluster name, systems in the cluster, and a Cluster Manager user "admin" with the password "password."

The following is an example of the main.cf for cluster "demo" and systems "SystemA" and "SystemB."