How do I change the hostname? In particular, what is the difference between /etc/hosts and /etc/sysconfig/network files? Where should I make the changes?
change /etc/sysconfig/netowrk and make the hostname=server.domain.com
change localhostnames add the new hostname to the file
change etc/hosts xx.xx.xx.xx server.domain.com server
restart the computer. You need to do this. Yes, you need to restart/reboot it.
then run these commands. (assumes your hostname is mail.example.com)
if any of these do not jibe, more to do until you get it right.
shell prompt> uname -n mail.example.com shell prompt> hostname -s mail shell prompt> hostname -d example.com shell prompt> hostname -f mail.example.com shell prompt> hostname mail.example.com
Lastly, you need to redo your certifercates for your computer since they (your openssh and maybe some others) are set up for the previous domain. In actual practice you may seldom see any issues with this, but the error messages will appear for some users trying to access different things....
Also, if you have stuff like logwatch or other system things going to a local mail make sure spamassassin or procmail rules are updated to deal with the change in localhost.localdomain so they are not junked.
Always make sure the normal things you are used to are still happening or being received after you change the hostname....many things can be affected, slightly or more, when doing it. Nothing usually server breaking.
This should do you well