rpc.idmapd: nss_getpwnam: name 'root@localdomain' does not map into domain 'mydomain.net'
This error doesn't appear to cause any issues but I don't like that sort of thing constantly spamming my logs so I wanted to fix it. So, it turns out that RHEL6/CentOS6 has a dodgy default configuration for the rpcidmapd service that you need to fix.
Edit this file:
# vi /etc/idmapd.conf
Find the setting for "Domain" which is incorrectly set to an edu domain and change it so that it is like this:
Domain = localdomain
Restart the service:
# service rpcidmapd restart
After this you should no longer get the above error in your system log.