Heartbeat

Heartbeat is a daemon that handles all the failover in the cluster. For starters, see http://linux-ha.org/ . We are running Heartbeat V2.

crm_resource

crm_resource is a command that lets you manage resources in the cluster.

crm_resource -W -r <resource>

Tells you where the specified resource is running

crm_resource -M -r <resource> [-h host]

Migrates the specified resource off of its current host. If -h is specified, it moves it to that host. This adds a location constraint with a score of -INFINITY for the resource and its current host (translation: the resource will never be run on its current host again), so you probably want to run

crm_resource -U -r <resource>

to remove this rule.

hb_gui

hb_gui is a graphical interface to the heartbeat cluster. It's quite nice, and is also very useful for configuring services.

Notes

• The raw configuration file is in /var/lib/heartbeat/crm/cib.xml . Never edit this file by hand- use cibadmin to add stuff to it. Better yet, use the gui.
• When configuring drbd stuff, use "drbddisk" instead of "drbd". The "drbd" resource is a V2 one that uses some complex master-slave stuff. Supposedly it can do cool stuff if it's set up correctly, but otherwise it's just confusing. "drbddisk" is much simpler and Just Works.