How to change a server's hostname

Update the following files:

• /etc/hosts
• /etc/hostname

Ubuntu 18.04

See current hostname and related info:

hostnamectl

Change hostname:

hostnamectl set-hostname my_new_hostname

Update /etc/hosts if necessary.

If cloud-init is installed, edit /etc/cloud/cloud.cfg

preserve_hostname: true

Postfix

• update /etc/mailname
• update /etc/postfix/main.cf
• restart postfix