chnage hostname just do :
# pico /etc/hosts
change the line from plain.rackshack.net to sub.domain.com sub
# pico /etc/sysconfig/network
change the "plain.rackshack.net" part of the second line to "sub.domain.com" (should be same as /etc/hosts)
# hostname sub.domain.com
the last bit should be everything, open i new SSH window and you should now have user@root user at the command prompt
Chris