Managing HP Serviceguard for Linux, Tenth Edition, September 2012

Safeguarding against Loss of Name Resolution Services
When you employ any user-level Serviceguard command (including cmviewcl), the
command uses the name service you have configured (such as DNS) to obtain the
addresses of all the cluster nodes. If the name service is not available, the command
could hang or return an unexpected networking error message.
NOTE: If such a hang or error occurs, Serviceguard and all protected applications will
continue working even though the command you issued does not. That is, only the
Serviceguard configuration commands (and corresponding Serviceguard Manager
functions) are affected, not the cluster daemon or package services.
The procedure that follows shows how to create a robust name-resolution configuration
that will allow cluster nodes to continue communicating with one another if a name
service fails.
1. Edit the /etc/hosts file on all nodes in the cluster. Add name resolution for all
heartbeat IP addresses, and other IP addresses from all the cluster nodes; see
“Configuring Name Resolution” (page 159) for discussion and examples.
NOTE: For each cluster node, the public-network IP address must be the first address
listed. This enables other applications to talk to other nodes on public networks.
2. If you are using DNS, make sure your name servers are configured in /etc/
resolv.conf, for example:
domain cup.hp.com
search cup.hp.com hp.com
nameserver 15.243.128.51
nameserver 15.243.160.51
3. Edit or create the /etc/nsswitch.conf file on all nodes and add the following
text, if it does not already exist:
• for DNS, enter (two lines):
hosts: files [NOTFOUND=continue UNAVAIL=continue] dns [NOTFOUND=return UNAVAIL=return]
• for NIS, enter (two lines):
hosts: files [NOTFOUND=continue UNAVAIL=continue] nis [NOTFOUND=return UNAVAIL=return]
If a line beginning with the string hosts: already exists, then make sure that the
text immediately to the right of this string is (on one line):
files [NOTFOUND=continue UNAVAIL=continue] dns [NOTFOUND=return UNAVAIL=return]
or
files [NOTFOUND=continue UNAVAIL=continue] nis [NOTFOUND=return UNAVAIL=return]
This step is critical, allowing the cluster nodes to resolve hostnames to IP addresses
while DNS, NIS, or the primary LAN is down.
Preparing Your Systems 161