I am about to configure two Nagios servers with one being a hot-standbye or failover unit. It will periodically check the active Nagios server and will need to steal its IP addresses in the case of failure.
My first instinct it to just script this using bash and cron, which should be fairly trivial. Is there a better utility for taking over another servers IPs? Perhaps one that would allow the previously active server to steal it's IPs back when it comes back online.
take a look at linux-ha. it is a cluster software which allows you to do what you plan without scripting anything.
you would basically define a service in the linux-ha configuration which consists of a virtual ip address and the nagios daemon process. with linux-ha you install some agents on both systems. they exchange heartbeats and will detect a failure of the active node. in this case linux-ha will run shutdown scripts on the failed node for your ip and nagios (default init script) and run a startup on the standby server.
the configuration is very well documented and there are some examples which will help you to get your cluster running.
You can use Centreon, which is a free Nagios configuration tool. It can manage multiple nagios server from a central console, as part of the features.
If you just "share" the ip, you will have logs on both servers. When looking at alert history, you will have to scroll the 2 servers, which is not efficient. You will have to manually sync the config folder and plugins folder too.
