Hostname is a name associated to computer which is connected to network. Hostname is used to identify this computer over the network. During setup process of Ubuntu you are asked to specify hostname. But later on you can change it. Here is how.
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Change a hostname with restart
Follow next steps to change host name of your computer. You need to edit those two files – /etc/hostname and /etc/hosts. First file is a simple one line file that just contains name of the host. Edit it with your favorite editor – vi or gedit.
howopensource@esprimo:~$ sudo gedit /etc/hostname
Second file /etc/hosts maps IP addresses to host names. So you need to edit it also, because some strange errors will start to appear.
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howopensource@esprimo:~$ sudo gedit /etc/hosts
Finally you should restart your Ubuntu box.
sudo reboot
Change a hostname without a reboot
If it is a server and you cannot reboot it – you can use command hostname. Without parameter command simply prints hostname to the terminal. With parameter command sets specified parameter to a new hostname. Note that command does not change file /etc/hostname and /etc/hosts. You still need to edit both files manually.
NOTE: You need to perform the same steps as above but instead to restart just use command hostname
howopensource@esprimo:~$ hostname esprimo howopensource@esprimo:~$ sudo hostname esprimo2 howopensource@esprimo:~$ hostname esprimo2 howopensource@esprimo:~$
Here is the output of those two file:
howopensource@esprimo:~$ more /etc/hostname esprimo howopensource@esprimo:~$ howopensource@esprimo:~$ howopensource@esprimo:~$ howopensource@esprimo:~$ more /etc/hosts 127.0.0.1 localhost 127.0.1.1 esprimo # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters howopensource@esprimo:~$
Ubuntu special command hostnamectl
From Ubuntu 13.04 there is a new command that can be used together with the old one and does the similar job. Once Ubuntu migrate to Systemd – most probably the old command will disappear and the new one will replace it.
howopensource@esprimo:~$ hostnamectl --help
hostnamectl [OPTIONS...] COMMAND ...
Query or change system hostname.
-h --help Show this help
--version Show package version
--transient Only set transient hostname
--static Only set static hostname
--pretty Only set pretty hostname
-P --privileged Acquire privileges before execution
--no-ask-password Do not prompt for password
-H --host=[USER@]HOST Operate on remote host
Commands:
status Show current hostname settings
set-hostname NAME Set system hostname
set-icon-name NAME Set icon name for host
set-chassis NAME Set chassis type for host
howopensource@esprimo:~$
Here is how to see the hostname using new command hostnamectl. Command also displays some other useful information.
howopensource@esprimo:~$ hostnamectl status
Static hostname: esprimo
Icon name: computer-desktop
Chassis: desktop
Machine ID: 813e56ef1c4f171bda95b46b5448007c
Boot ID: c719696ace224abf91fc52d6d9f83016
Operating System: Ubuntu 14.10
Kernel: Linux 3.16.0-29-generic
Architecture: x86_64
howopensource@esprimo:~$
Here is how to set a hostname without to restart server using new command.
howopensource@esprimo:~$ hostnamectl set-hostname esprimo2
And here is again how to display status and to check that update happens but using new and old command
howopensource@esprimo:~$ hostnamectl status Static hostname: esprimo2 howopensource@esprimo:~$ hostname esprimo2
What happens if you forgot to change /ect/hosts
File /ets/hosts maps IP addresses and names of hosts. If you forgot to change hostname in that file then it cannot be resolved and strange errors will start to appear and main error will be unable to resolve host hostname.
howopensource@esprimo:~$ hostname
esprimo
howopensource@esprimo:~$ sudo hostname esprimo2
howopensource@esprimo:~$ sudo gedit /etc/hostname
sudo: unable to resolve host esprimo2
No protocol specified
** (gedit:3266): WARNING **: Could not open X display
No protocol specified
gdk_mir_display_open
Failed to connect to Mir: Failed to connect to server socket: No such file or directory
(gedit:3266): Gtk-WARNING **: cannot open display: :0
howopensource@esprimo:~$
Hostnames are human-readable names of computers that correspond to the address of a device connected to a network. They are used by various naming schemes and systems such as DNS (Domain Name System) and the meaning of hostname will vary according to the naming system used. Hostnames are typically used in an administrative capacity and may appear in computer browser lists, active directory lists, IP address to hostname resolutions, email headers, etc. More you can read from this article about hostnames from Wikipedia.