Linux service

From CauchoWiki

Thanks to Guy McArthur and Carlos Hanson for the examples and much of the explanation for this tutorial.

[edit] Modifying httpd.sh

The easiest way to start Resin when Linux boots is to modify your httpd.sh and create symbolic link in /etc/rc.d/rc3.d and /etc/rc.d/rc5.d. Because the boot process does not set environment variables, you'll need to set them in the httpd.sh.

1. Copy httpd.sh to "resin-a.sh" in resin/bin and change permissions.
2. Configure JAVA_HOME, RESIN_HOME, PATH, and "-pid" in resin-a.sh.
3. Check that "resin-a.sh start" and "resin-a.sh stop" work from the command line when running as root.
4. "ln -s /usr/local/resin/bin/resin-a.sh /etc/rc.d/rc3.d/S86resin-a"
5. "ln -s /usr/local/resin/bin/resin-a.sh /etc/rc.d/rc5.d/S86resin-a"
6. "ln -s /usr/local/resin/bin/resin-a.sh /etc/rc.d/rc2.d/K14resin-a"
7. Reboot to test.

A sample resin-a.sh might look like:

#! /bin/sh
#
# ...
#
JAVA_HOME=/usr/java
export JAVA_HOME
 
RESIN_HOME=/usr/local/resin
export RESIN_HOME
 
PATH=/bin:/usr/bin:/usr/local/bin
export PATH

args="-Xms75M -Xmx100M start -pid $RESIN_HOME/resin-a.pid"
class=com.caucho.server.http.HttpServer
name=httpd
 
perl=/usr/local/bin/perl
 
exec $perl $RESIN_HOME/bin/wrapper.pl -chdir -name "$name" \
                                      -class "$class" $args $*

An advantage of this method is that you can use the same script to start and start the server interactively.

[edit] Linux booting background

At startup, Linux runs the /etc/rc.d/rc script at the current runlevel (normally 3 or 5). All the Sxx scripts in /etc/rc.d/rc3.d/S* are started in order.

for i in /etc/rc$runlevel.d/S*; do
  $i start
done

So S86resin-a will be called as "S86resin-a start" as the root user. Since the script can't assume any environment variables, it needs to set them itself.

Since Resin is an application, as opposed to a system service, it should be started late in the boot process. S86 is a decent choice. The specific order only matters if your startup depends on another service. For example, if you have a load-on-startup servlet that depends on a database, the database should be S85 or lower.

Some configurations boot up in runlevel 3 and others boot in runlevel 5. The actual boot order will then be {1,2,3} or {1,2,5}. A machine booting with runlevel 3 will have /etc/inittab with the following line:

id:3:initdefault

On server shutdown, Linux calls the scripts in /etc/rc.d/rc2.d/K* in order.

for i in /etc/rc$runlevel.d/K*; do
  $i stop
done

In this case, Resin is an application, as opposed to a system service, it should be killed early in the shutdown process.

[edit] Alternatives

An alternative to modifying the httpd.sh is to create another script that passes arguments to the original httpd.sh.

#!/bin/sh 

# script name: resin 
# 
# start/stop script for Resin 

RESIN_HOME=/usr/resin 
JAVA_HOME=/usr/java/jdk1.3 
PATH="$PATH:/usr/java/jdk1.3/bin:/usr/X11R6/bin" 
export PATH JAVA_HOME RESIN_HOME 

${RESIN_HOME}/bin/httpd.sh -Xms75M -Xmx100M -java_home ${JAVA_HOME} "$*" 

Guy McArthur writes

I find it a bit easier to edit wrapper.pl rather than creating a script that passes in environment variables. But that's just because I'll be starting/stopping resin manually using httpd.sh to try something out, so having that single point of control is good.

Carlos Hanson writes:

I originally started by editing wrapper.pl, but having a script that passes the necessary arguments to httpd.sh allows me to reinstall or upgrade Resin more easily. All I have to worry about is configuration files. This is important when dealing with developers new to Unix and maintaining a large number of production and development servers. We keep the script and the conf files in source control.