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 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

       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/