How to change system hostname in Linux ?

Recently  we got a request from one of our  visitor to post article related to hostname change in Linux operating systems. I am going to cover this  now.

There are two general way to do this 

1)  Temporary 

2)  Permanent

First we go and learn about how to check host name (system name) of the server.

Use "hostname" command to list the system system name.

[root@umser1 ~]# hostname umser1.unixmantra.com [root@umser1 ~]#

    -s, --short              short host name

    -a, --alias               alias names

    -i, --ip-address      addresses for the hostname

    -I, --all-ip-addresses all addresses for the host

    -f, --fqdn, --long    long host name (FQDN)

    -A, --all-fqdns        all long host names (FQDNs)

    -d, --domain           DNS domain name

    -y, --yp, --nis          NIS/YP domainname

    -F, --file                  read hostname or NIS domainname from given fil

In Cent OS  we have another command additionally 

[root@umser1 ~]# sysctl kernel.hostname

kernel.hostname = umser1.unixmantra.com

[root@umser1 ~]#

Change the hostname on a running system (Temporarily) :

This is pretty simple  

#hostname  new-name

will set the hostname of the system to  new-name. This is active right away and will remain like that until the system will be rebooted (because at system boot it will set this from some particular file configurations – see bellow how to set this permanently). You will most probably need to exit the current shell in order to see the change in your shell prompt.

How Do I Change Hostname Permanently?

For Debian  Systems:

Debian based systems use the file /etc/hostname to read the hostname of the system at boot time and set it up using the init script /etc/init.d/hostname.sh

# /etc/hostname

umser2.unixmantra.com

So on a Debian based system we can edit the file /etc/hostname and change the name of the system and then run:

/etc/init.d/hostname.sh start

to make the change active. The hostname saved in this file (/etc/hostname) will be preserved on system reboot (and will be set using the same script we used hostname.sh).

For Redhat/Fedora/Cent OS Systems:

As you know if you need  changes to be  permanent   you need to hard-code the relevant configuration files.

To make the hostname name permanent in  RH variants ,you must edit the /etc/sysconfig/network file to change  "HOSTNAME" value to your new hostname.

#vi /etc/sysconfig/network

NETWORKING=yes

HOSTNAME="umser2.unixmantra.com"

GATEWAY="192.168.1.1"

GATEWAYDEV="eth0"

FORWARD_IPV4="yes"

Verification:

Open new session and  there you go ,we can  see our  new hostname

[root@umser2 ~]# hostname

umser2.unixmantra.com

[root@umser2 ~]#