https://habrahabr.ru/post/280037/

hostnamectl
    hostname
    set-hostname EPBYGOMW0024T.
/etc/hostname
    old-way to set persistent

sudo systemctl restart systemd-hostnamed
  it is terminated when unused

hostname
hostname -f
uname -n

hostname <new-host-name>
    temp set a new host name

/etc/machine-info
PRETTY_HOSTNAME="bla-bla'bla-bla"

DNS:
getent hosts
    get hosts info

/etc/nsswitch.conf
hosts: files dns

/etc/resolv.conf
search example.com

dig [+short]