Managing HP Serviceguard A.11.20.10 for Linux, December 2012

Serviceguard nodes can communicate over any of the cluster’s shared networks, so the network
resolution service you are using (such as DNS, NIS, or LDAP) must be able to resolve each of their
primary addresses on each of those networks to the primary hostname of the node in question.
In addition, HP recommends that you define name resolution in each node’s /etc/hosts file,
rather than rely solely on a service such as DNS. Configure the name service switch to consult the
/etc/hosts file before other services. See “Safeguarding against Loss of Name Resolution
Services” (page 133) for instructions.
NOTE: If you are using private IP addresses for communication within the cluster, and these
addresses are not known to DNS (or the name resolution service you use) these addresses must
be listed in /etc/hosts.
For requirements and restrictions that apply to IPv6–only clusters and mixed-mode clusters, see
“Rules and Restrictions for IPv6-Only Mode” (page 84) and “Rules and Restrictions for Mixed
Mode” (page 85), respectively, and the latest version of the Serviceguard release notes.
For example, consider a two node cluster (gryf and sly) with two private subnets and a public
subnet. These nodes will be granting access by a non-cluster node (bit) which does not share the
private subnets. The /etc/hosts file on both cluster nodes should contain:
15.145.162.131 gryf.uksr.hp.com gryf
10.8.0.131 gryf.uksr.hp.com gryf
10.8.1.131 gryf.uksr.hp.com gryf
15.145.162.132 sly.uksr.hp.com sly
10.8.0.132 sly.uksr.hp.com sly
10.8.1.132 sly.uksr.hp.com sly
15.145.162.150 bit.uksr.hp.com bit
Keep the following rules in mind when creating entries in a Serviceguard node's/etc/hosts:
1. NODE_NAME in the cluster configuration file must be identical to the hostname which is the
first element of a fully qualified domain name (a name with four elements separated by periods).
This hostname is what is returned by the hostname(1) command. For example, the
NODE_NAME should be gryf rather than gryf.uksr.hp.com. For more information, see
the NODE_NAME entry under “Cluster Configuration Parameters ” (page 86).
NOTE: Since Serviceguard recognizes only the hostname, gryf.uksr.hp.com and
gryf.cup.hp.com cannot be nodes in the same cluster, Serviceguard identifies them as the
same host gryf.
2. All primary IP addresses configured.
NOTE: Serviceguard recognizes only the hostname (the first element) in a fully qualified domain
name (a name like those in the example above). This means, for example, that gryf.uksr.hp.com
and gryf.cup.hp.com cannot be nodes in the same cluster, as Serviceguard would see them
as the same host gryf.
If applications require the use of hostname aliases, the Serviceguard hostname must be one of the
aliases in all the entries for that host. For example, if the two-node cluster in the previous example
were configured to use the alias hostnames alias-node1 and alias-node2, then the entries
in /etc/hosts should look something like this:
15.145.162.131 gryf.uksr.hp.com gryf1 alias-node1
10.8.0.131 gryf.uksr.hp.com gryf2 alias-node1
10.8.1.131 gryf.uksr.hp.com gryf3 alias-node1
15.145.162.132 sly.uksr.hp.com sly1 alias-node2
10.8.0.132 sly.uksr.hp.com sly2 alias-node2
10.8.1.132 sly.uksr.hp.com sly3 alias-node2
132 Building an HA Cluster Configuration