HOSTNAME(5) hostname HOSTNAME(5)
NAME
hostname - Local hostname configuration file
SYNOPSIS
/etc/hostname
DESCRIPTION
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
systemd(1) and the associated tools will obtain the hostname in the
following ways:
• If the kernel commandline 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
The simple configuration file format of /etc/hostname originates from
Debian GNU/Linux.
SEE ALSO
systemd(1), sethostname(2), hostname(1), hostname(7), machine-id(5),
machine-info(5), hostnamectl(1), systemd-hostnamed.service(8), systemd-
firstboot(1)
NOTES
1. NetworkManager
https://developer.gnome.org/NetworkManager/stable/
systemd 252 HOSTNAME(5)
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