Today I find myself having to change the domain name of my server. Here are the steps, though the order can be shuffled.

File names on the server

In case I ever need to do it again, I am changing the directory name on the server which files are served from. Instead of

/var/www/myjetsonnano.olddomainname.com

files will now be located in

/var/www/myjetsonnano

Apache2 Sites-Available

Go into the directory and the edit file

/etc/apache2/sites-available/
site.newdomainname.com.conf

replacing all references to the old domain name with the new domain name. The new file can be created by copying the old one, or renaming it if you feel confident.

Enable the site and get an SSL certificate

a2ensite site.newdomain.com
systemctl reload apache2
certbot --apache -d site.newdomain.com

Temporary domain name override in WordPress

To get wordpress back up running, it needs to know the domain name, which is normally stored in its database, but which can be overridden by a couple of lines in the file

wp-config.php

by adding lines like

define('WP_HOME','https://site.newdomain.com');
define('WP_SITEURL','https://site.newdomain.com');

Cleaning up wordpress

When wordpress is working, any old links can be tidied up using this tool.