Intro To 'hostname' Command In Linux

2024-04-21 - By Robert Elder

I use the 'hostname' command, to print the hostname of the current machine:

hostname

robert-ThinkPad-P15v-Gen-1

A hostname is the name that's used to identify a particular machine on a computer network.

Usually, this hostname will also be associated with an IP address. You can use commands like the 'dig' command to check what this IP address is:

dig +short $(hostname)

127.0.1.1

Multiple Versions Of 'hostname' Command

The 'hostname' command has multiple different common implementations, and this can lead to confusing results. For example, if I use the version of 'hostname' that's built-into my system on Ubuntu:

hostname -i

I'll see this result:

127.0.1.1

However, if I try to use the version of 'hostname' from Core Utils:

./coreutils-9.4/src/hostname -i

I'll see this result:

./coreutils-9.4/src/hostname: invalid option -- 'i'
Try './coreutils-9.4/src/hostname --help' for more information.

GNU Core Utils 'hostname' Command

The GNU Core Utils implementation of the 'hostname' command is very simple and only supports reading or writing a machine's host name:

info hostname

Next: hostid invocation,  Prev: uname invocation,  Up: System context

21.5 ‘hostname’: Print or set system name
=========================================

With no arguments, ‘hostname’ prints the name of the current host
system.  With one argument, it sets the current host name to the
specified string.  You must have appropriate privileges to set the host
name.  Synopsis:

     hostname [NAME]

   The only options are ‘--help’ and ‘--version’.  *Note Common
options::.

   ‘hostname’ is not installed by default, and other packages also
supply a ‘hostname’ command, so portable scripts should not rely on its
existence or on the exact behavior documented above.

   An exit status of zero indicates success, and a nonzero value
indicates failure.

Net Tools 'hostname' Command

For the reasons noted above, a different implementation of the 'hostname' command also exists in the 'net-tools' package, which supports many more flags and options:

hostname --help

Usage: hostname [-b] {hostname|-F file}         set host name (from file)
       hostname [-a|-A|-d|-f|-i|-I|-s|-y]       display formatted name
       hostname                                 display host name

       {yp,nis,}domainname {nisdomain|-F file}  set NIS domain name (from file)
       {yp,nis,}domainname                      display NIS domain name

       dnsdomainname                            display dns domain name

       hostname -V|--version|-h|--help          print info and exit

Program name:
       {yp,nis,}domainname=hostname -y
       dnsdomainname=hostname -d

Program options:
    -a, --alias            alias names
    -A, --all-fqdns        all long host names (FQDNs)
    -b, --boot             set default hostname if none available
    -d, --domain           DNS domain name
    -f, --fqdn, --long     long host name (FQDN)
    -F, --file             read host name or NIS domain name from given file
    -i, --ip-address       addresses for the host name
    -I, --all-ip-addresses all addresses for the host
    -s, --short            short host name
    -y, --yp, --nis        NIS/YP domain name

Description:
   This command can get or set the host name or the NIS domain name. You can
   also get the DNS domain or the FQDN (fully qualified domain name).
   Unless you are using bind or NIS for host lookups you can change the
   FQDN (Fully Qualified Domain Name) and the DNS domain name (which is
   part of the FQDN) in the /etc/hosts file.

Check Which Version Of 'hostname' You Have

On my Ubuntu 20 machine, the 'info' pages show documentation for the Core Utils version of hostname, while the 'man' pages show documentation for the 'net-tools' version of hostname. On my machine, invoking the 'hostname' command appears to run the 'net-tools' version. This will likely be different on your distribution. You can investigate which version you likely have by running 'hostname' with the '--version' flag:

hostname --version

or, by checking the 'man' and 'info' pages:

man hostname
info hostname

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