hostname

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:

       o   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),

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

       o   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.

       o   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 249                                                        HOSTNAME(5)