The sys admin's daily grind: Keepalived
Fit Without a Pacemaker
Columnist Charly likes to keep system-critical daemons on two or more servers. If one of the servers fails, the idea is that the service can be started on the other and will be available at the same IP address – a scenario that works with or without the Pacemaker heartbeat.
Services without which nothing works are clear candidates for doppelgängers on my network. If the master fails, or if I just need to shut down the server for maintenance, I want the service automatically to start on the second server and to be available on the same IP address as before, if possible.
To do this, the IP address needs to migrate quickly and without much overhead to the backup machine. Addresses like this are known as floating IPs. The migration helpers here are Pacemaker [1] and Corosync [2]. These tools can't do much more than facilitate the move, however, so the solution seems a little over the top for a simple failover scenario.
A more streamlined solution called Keepalived [3] is part of the default toolset in most distributions. I just installed Keepalived and jumped in feet first. What I found were two servers with IP addresses 10.0.0.1 and 10.0.0.2. My floating IP of choice is 10.0.0.100.
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