Apache Reference: http_core, PidFile
Process ID File
Syntax: PidFile A
Example: PidFile /var/run/apache.pid
Since: Apache 1.0
This directive sets the file to which the server records the
process ID of the daemon (actually, the PID of the parent server
process). If the file argument does not begin with a slash
(C), then it is assumed to be relative to ServerRoot.
The PidFile is used only in stand-alone mode. It is often
desirable to send a signal to the server, so that it closes and
then reopens its ErrorLog and TransferLog, and rereads its
configuration files. This task is accomplished by sending a
SIGHUP signal to the process ID listed in the PidFile.