How do I restart my lighttpd+php fastcgi web server gracefully under Linux / UNIX operating systems?

You need to send a SIGINT single to lighttpd process. It will only shutdown the server after the client connections are closed successfully without interrupting the connections. This is useful for reloading configuration options. If you are using sysv style script, make sure reload() looks like as follows:

#!/bin/bash
 
# only works under RHEL / Fedora / CentOS Linux
source /etc/init.d/functions
 
pidfile=/var/run/lighttpd.pid
prog=lighttpd
conf=/etc/lighttpd/lighttpd.conf
lighttpd=/usr/sbin/lighttpd
 
reload(){
  echo -n $"Reloading $prog  "
  killproc -p $pidfile $prog -INT
  start
  local RETVAL=$?
  echo
  return $RETVAL
} 
 
start() {
        echo -n $"Starting $prog: "
        daemon $lighttpd -f $conf
        RETVAL=$?
        echo
        [ $RETVAL -eq 0 ] && touch /var/lock/subsys/$prog
        return $RETVAL
}
 
stop() {
        echo -n $"Stopping $prog: "
        killproc $lighttpd
        RETVAL=$?
        echo
        [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/$prog
        return $RETVAL
}
 
case "$1" in
        start)
                start
                ;;
        stop)
                stop
                ;;
        restart)
                stop
                start
                ;;
        condrestart)
                if [ -f /var/lock/subsys/$prog ]; then
                        stop
                        start
                fi
                ;;
        reload)
                reload
                ;;
        status)
                status $lighttpd
                RETVAL=$?
                ;;
        *)
                echo $"Usage: $0 {start|stop|restart|condrestart|reload|status}"
                RETVAL=1
esac
exit $RETVAL

Command line options for UNIX / Linux

If you do not have /init.d/ or /rc.d/ style script use the following procedure. You can send INT single from command line itself and start server again:
# kill -INT $(cat /var/run/lighttpd.pid)
# lighttpd -f /etc/lighttpd.conf
You should see something as follows in your lighttpd error log file:

2009-05-08 18:54:45: (server.c.1355) [note] graceful shutdown started 
2009-05-08 18:54:45: (log.c.97) server started 
2009-05-08 18:54:49: (server.c.1469) server stopped by UID = 0 PID = 957 
2009-05-08 18:56:57: (log.c.97) server started 

A note about php fastcgi process

Make sure php socket configured as follows (without the following config, php will not get reloaded after graceful restart):

"socket" => "/tmp/php-cgi.socket" + var.PID

Here is a sample php5 fastcgi lighttpd.conf configuration:

fastcgi.server    = ( ".php" =>
        ((
                "bin-path" => "/usr/bin/php-cgi",
                "socket" => "/tmp/php-cgi.socket"+ var.PID,
                "max-procs" => 1,
                "idle-timeout" => 30,
                "bin-environment" => (
                        "PHP_FCGI_CHILDREN" => "2",
                        "PHP_FCGI_MAX_REQUESTS" => "2000"
                ),
                "bin-copy-environment" => (
                        "PATH", "SHELL", "USER"
                ),
                "broken-scriptfilename" => "enable"
        ))
)

A note about RHEL / CentOS Linux init.d script

Most modern Linux distributions comes with a script to start / stop / restart and reload lighttpd:
# /etc/init.d/lighttpd reload
However, you need to patch up /etc/init.d/lighttpd under RHEL / CentOS Linux. Find reload():

reload() {
        echo -n $"Reloading $prog: "
        killproc $lighttpd -HUP
        RETVAL=$?
        echo
        return $RETVAL
}

Replace with:

reload() {
        echo -n $"Reloading $prog: "
        killproc $lighttpd -INT
        RETVAL=$?
        echo
        return $RETVAL
}

Debian / Ubuntu Linux users

If you are using Debian / Ubuntu Linux, enter:
# /etc/init.d/lighttpd reload