Restarts (Apache: The Definitive Guide, 3rd Edition)

3.6. Restarts

A webmaster will sometimes want to kill Apache and restart it with a new Config file, often to add or remove a virtual host as people's web sites come and go. This can be done the brutal way, by running ps -aux to get Apache's PID, doing kill <PID> to stop httpd and restarting it. This method causes any transactions in progress to fail in an annoying and disconcerting way for logged-on clients. A recent innovation in Apache allowed restarts of the main server without suddenly chopping off any child processes that were running.

There are three ways to restart Apache under Unix (see Chapter 2):

Kill and reload Apache, which then rereads all its Config files and restarts:
```
% kill PID
% httpd [flags]
```
The same effect is achieved with less typing by using the flag-HUP to kill Apache:
```
% kill -HUP PID
```

A graceful restart is achieved with the flag-USR1. This rereads the Config files but lets the child processes run to completion, finishing any client transactions in progress, before they are replaced with updated children. In most cases, this is the best way to proceed, because it won't interrupt people who are browsing at the time (unless you messed up the Config files):

% kill -USR1
PID

A script to do the job automatically (assuming you are in the server root directory when you run it) is as follows:

#!/bin/sh
kill -USR1 `cat logs/httpd.pid`

Under Win32 it is enough to open a second MS-DOS window and type:

apache -k shutdown|restart

See Chapter 2.