Custom Hostname on cPanel

hi to all!
I'm a newbie on Cpanel management.
I bought a VPS with cpanel onboard.
I've seen that i can customize my "hostname" for the V-server
Wich is the correct way to do it??
I've just a domain registered with DNS control zone. i tried to set in Cpanel vps01.mydomain.com but i get some error message.. so i think something goes wrong:


Traceback (most recent call last):
File "/usr/local/cpanel/bin/reset_mailman_hostname", line 44, in
raise SystemExit(main(sys.argv))
File "/usr/local/cpanel/bin/reset_mailman_hostname", line 31, in main
file=open('/usr/local/cpanel/3rdparty/mailman/lists/' + list + '/config.pck','r')
IOError: [Errno 2] No such file or directory: '/usr/local/cpanel/3rdparty/mailman/lists/mailman/config.pck'

What mean exactly this message? Many thanks

 

Well i ran the script and no error went out..
Finished with "maintenance complete" And i suppose there's a log in the path he showed me.
How i can check if everything is really ok?
Sorry but i'm not a linux-user.. so is difficult for me operate on the shell