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NAME | SYNOPSIS | DESCRIPTION | HOSTNAME SEMANTICS | HISTORY | SEE ALSO | NOTES | COLOPHON |
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HOSTNAME(5) hostname HOSTNAME(5)
hostname - Local hostname configuration file
/etc/hostname
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.
If the question mark character "?" appears in the hostname, it is
automatically substituted by a hexadecimal character derived from
the machine-id(5) when applied, securely and deterministically by
cryptographic hashing. Example: "foobar-????-????" will
automatically expand to "foobar-92a9-061c" or similar, depending
on the local machine ID.
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.
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.
The simple configuration file format of /etc/hostname originates
from Debian GNU/Linux.
systemd(1), sethostname(2), hostname(1), hostname(7),
machine-id(5), machine-info(5), hostnamectl(1),
systemd-hostnamed.service(8), systemd-firstboot(1)
1. NetworkManager
https://developer.gnome.org/NetworkManager/stable/
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 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) 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
[email protected]
systemd 258~rc2 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)
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HTML rendering created 2025-09-06 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. |
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