change hostname without rebooting

[Zenaan Harkness <zen@freedbms.net>]

So I change hostname from "localhost" to "x".
I run /etc/init.d/hostname.sh start

I'm still logged in. I have many firefox tabs open. Actually, I
changed the hostname a day ago.

Now, when I try to start an xterm, it takes about 9s.

I run xterm from an existing xterm, to see what might be happening,
and I get these errors:
_IceTransSocketUNIXConnect: Cannot connect to non-local host localhost
_IceTransSocketUNIXConnect: Cannot connect to non-local host localhost
Warning: Tried to connect to session manager, Could not open network socket

I'm running wheezy, xfce4, systemd, amd64.

tia
zenaan