Apache, nginx and LiteSpeed.
WHAT TO ESTABLISH FIRST
Which web server is actually running.
HOW
List listening processes on the web ports.
WHY IT MATTERS
Commands and file locations differ entirely between them.
WHERE CONFIGURATION USUALLY LIVES
Under etc, in a directory named after the server.
WHAT A VIRTUAL HOST IS
Configuration for one site on a server hosting many.
WHAT TO CHECK WHEN A SITE DOES NOT LOAD
Whether the service is running Whether it is listening on the expected port Whether the virtual host exists and points at the right directory Whether the document root has correct permissions What the error log says
WHY THE ERROR LOG LAST IN THE LIST BUT FIRST IN PRACTICE
It usually contains the answer, but only if the service is running at all.
WHAT TO DO BEFORE RESTARTING AFTER A CONFIGURATION CHANGE
Test the configuration with the server's own check command.
WHY
A syntax error prevents the service starting, taking every site down.
WHAT reload DOES INSTEAD OF restart
Applies changes without dropping existing connections.
WHAT TO CHECK AFTER ANY CHANGE
That sites still respond, using curl against the server itself.
WHAT NOT TO EDIT ON A CONTROL PANEL SERVER
Generated configuration, which is overwritten.
WHAT TO USE INSTEAD
The include mechanism the panel provides.
