- Red Hat Enterprise Linux (RHEL) with the High Availability Add-On
- Should cluster node names and fence device host names be defined in /etc/hosts, or can I just rely on DNS to do lookups?
- What is the
/etc/hostsfile used for, and how should it be set up?
- How can I avoid fencing failing and/or nodes being unable to join a cluster when DNS lookups are not functioning?
- How to configure
/etc/hostsfile when configuring a two node Red Hat High Availability cluster?
- In Red Hat Enterprise Linux with the High Availability Add-On, the
/etc/hostsfile should be used to define the IP address and host names for all cluster nodes and fence devices. This is recommended to eliminate DNS as a single point of failure. Configuring the cluster software to use the preferred network interface often involves specifying the correct fully qualified name in the configuration, and so
/etc/hostsshould also list nodes in this format whenever possible:
<IP> <Fully Qualified Domain Name> <Short Name> 192.168.2.2 node1.example.com node1 192.168.2.3 node2.example.com node2
If only shortnames are desired to differentiate a specific node's address, they can be specified in
/etc/hosts in place of a fully qualified name:
<IP> <Short Name> 192.168.2.2 node1 192.168.2.3 node2
- Below is a complete example
/etc/hostsfor a three-node cluster with a single fence device per node:
# Do not remove the following line, or various programs # that require network functionality will fail. 127.0.0.1 localhost.localdomain localhost ::1 localhost6.localdomain6 localhost6 # cluster nodes. 192.168.2.201 cluster-1.example.com cluster-1 192.168.2.202 cluster-2.example.com cluster-2 192.168.2.203 cluster-3.example.com cluster-3 # fence devices. 192.168.2.204 node1-fence 192.168.2.205 node2-fence 192.168.2.206 node3-fence
Note: In the place of hostnames, the cluster configuration can use IP addresses for node names and fence device ipaddr values. If no hostnames are used to specify a node in the cluster configuration, then
/etc/hostsdoes not need to contain any specific entries for the cluster nodes.
Note: The use of DHCP for obtaining an ip address on an interface being used by corosync for heartbeat communication is unsupported
Further information on configuring a dedicated heartbeat network:
How do I configure cluster nodes to use a dedicated heartbeat interface?
Further information on how cluster resolves the configured node names:
What should I name my cluster nodes?
- Red Hat Enterprise Linux
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