This howto describes how to rename a Munin 1.4.x node and/or move it to another domain without losing history, because just renaming the node in /etc/munin/munin.conf will actually just create a new host. It has been tested on Debian Squeeze (would work on Debian Lenny too, at least when using 1.4 backports). You will need at least a basic understanding of how to configure Munin to use it.

1. Stop the cronjob (rename the /etc/cron.d/munin to something with a dot in the name, e.g: /etc/cron.d/munin.disabled)
2. Rename the RRD files. The following command does the job (actually, moved the files by hand to the right directory after renaming them):
   for file in /var/lib/munin/localdomain/*.rrd; do mv $file `echo $file|sed ‘s/localhost.localdomain/saidhost.example.net/’`; done
3. Edit /etc/munin/munin.conf to change the node name accordingly
4. Enable back the cronjob (renaming /etc/cron.d/munin.disabled to /etc/cron.d/munin)
5. Wait at least 5 minutes (the time for munin-update to run at least once)
6. Depending on your setup (if you are using Munin’s CGI mode), you might need to update some file and/or directory permissions
7. Go to the web interface to check the result