How to modify the hostname in Linux

Usually this is an easy task using the

hostname

command:

[root@blah ~]# hostname
blah
[root@blah ~]# hostname florian
[root@blah ~]# hostname
florian

But on some distributions, this procedure is not modifying the hostname permanently.

On Debian based systems you must:
1. edit /etc/hostname and put there whatever hostname you want to set;
2. run

/etc/init.d/hostname.sh start

on RedHat based systems you have to:
1. edit

/etc/sysconfig/network

and put on HOSTNAME stanza whatever you want.
2. Reboot.

You can modify the hostname also via sysctl command:
to read:

sysctl kernel.hostname

to modify:

sysctl kernel.hostname=blah