I would like to customize the standard maintenance page which gets shown during plugin updates.
For single sites the process is clear to me. Putting a maintenance.php
into /wp-content
.
But how does this work for subsites of a multisite install?
It works for the whole network, not for a specific sub site. Basically that mechanism is intended to be used when there is a software upgrade, time in which you don't want to have visitors on the site that might result in some data corruption (especialy logged in users, but not only).