man7.org > Linux > man-pages

Linux/UNIX system programming training

hostname(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | HOSTNAME SEMANTICS | HISTORY | SEE ALSO | NOTES | COLOPHON 

HOSTNAME(5)                     hostname                     HOSTNAME(5)

NAME         top

       hostname - Local hostname configuration file

SYNOPSIS         top

       /etc/hostname

DESCRIPTION         top

       The /etc/hostname file configures the name of the local system.
       Unless overridden as described in the next section, systemd(1)
       will set this hostname during boot using the sethostname(2)
       system call.

       The file should contain a single newline-terminated hostname
       string. Comments (lines starting with a "#") are ignored. The
       hostname should be composed of up to 64 7-bit ASCII lower-case
       alphanumeric characters or hyphens forming a valid DNS domain
       name. It is recommended that this name contains only a single
       label, i.e. without any dots. Invalid characters will be filtered
       out in an attempt to make the name valid, but obviously it is
       recommended to use a valid name and not rely on this filtering.

       You may use hostnamectl(1) to change the value of this file
       during runtime from the command line. Use systemd-firstboot(1) to
       initialize it on mounted (but not booted) system images.

HOSTNAME SEMANTICS         top

       systemd(1) and the associated tools will obtain the hostname in
       the following ways:

       •   If the kernel command line parameter systemd.hostname=
           specifies a valid hostname, systemd(1) will use it to set the
           hostname during early boot, see kernel-command-line(7),

       •   Otherwise, the "static" hostname specified by /etc/hostname
           as described above will be used.

       •   Otherwise, a transient hostname may be set during runtime,
           for example based on information in a DHCP lease, see
           systemd-hostnamed.service(8). Both NetworkManager[1] and
           systemd-networkd.service(8) allow this. Note that
           systemd-hostnamed.service(8) gives higher priority to the
           static hostname, so the transient hostname will only be used
           if the static hostname is not configured.

       •   Otherwise, a fallback hostname configured at compilation time
           will be used ("localhost").

       Effectively, the static hostname has higher priority than a
       transient hostname, which has higher priority than the fallback
       hostname. Transient hostnames are equivalent, so setting a new
       transient hostname causes the previous transient hostname to be
       forgotten. The hostname specified on the kernel command line is
       like a transient hostname, with the exception that it has higher
       priority when the machine boots. Also note that those are the
       semantics implemented by systemd tools, but other programs may
       also set the hostname.

HISTORY         top

       The simple configuration file format of /etc/hostname originates
       from Debian GNU/Linux.

SEE ALSO         top

       systemd(1), sethostname(2), hostname(1), hostname(7),
       machine-id(5), machine-info(5), hostnamectl(1),
       systemd-hostnamed.service(8), systemd-firstboot(1)

NOTES         top

        1. NetworkManager
           https://developer.gnome.org/NetworkManager/stable/

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
       a bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 257~devel                                            HOSTNAME(5)

Pages that refer to this page: hostnamectl(1),  systemd-firstboot(1),  machine-id(5),  machine-info(5),  os-release(5),  systemd.directives(7),  systemd.index(7),  systemd-hostnamed.service(8)

HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface.

For details of in-depth Linux/UNIX system programming training courses that I teach, look here.

Hosting by jambit GmbH.

Cover of TLPI