How do I find out my server name (machine name) under Linux operating systems using command shell?

You need to use the hostname command. It is used to either set or show the current host, domain or node name of the system. Open a command-line terminal (select Applications > Accessories > Terminal), and then type:
$ hostname
Sample outputs
vivek-laptop.nixcraft.in
Where,

• vivek-laptop : You computer name.
• nixcraft.in : Your dNS domain name.
• vivek-laptop.nixcraft.in : Your computer name with Fully Qualified Domain Name (FQDN).

To see the domain part of the FQDN (Fully Qualified Domain Name), enter:
$ dnsdomainname
Sample outputs:

nixcraft.in

How Do I Change My Hostname?

The hostname commands set the host name using the following syntax. Please note that only the super-user / root can change the names. To switch to the root user by typing su – and entering the root password, when prompted.
# hostname newhostname.nixcraft.in
# hostname laptop.nixcraft.net.in
You need to edit /etc/hostname or /etc/sysconfig/network file to set hostname permanently. See our previous FAQ about changing hostname using configuration files.