hostname — Local hostname configuration file
configures the name of the local system that is set
during boot using the
system call. It should contain a single
newline-terminated hostname string. The
hostname may be a free-form string up to 64 characters
in length; however, it is recommended that it consists
only of 7-bit ASCII lower-case characters and no spaces or dots,
and limits itself to the format allowed for DNS domain
name labels, even though this is not a
Depending on the operating system, other configuration files might be checked for configuration of the hostname as well, however only as fallback.
You may use hostnamectl(1) to change the value of this file from the command line.
The simple configuration file format of
/etc/hostname originates from