On Mon, 12 Jan 2004, salvatore wrote:
> Needless to say, Im a bit new at this. Ive been researching since your
> suggestion, and I havent found where a file in /etc/rc.d/init.d actually
> runs the application.
>From the looks of things you only looked at one "application" - there are
many others and this one is probably not the best example.
A very good example to follow would be "smartd" (if you have it on your
system) - I've pasted it below and commented it, it should be markedly
easy to adpat.
> For example, here is the contents of the yum file there:
> ***
> # cat yum
> #!/bin/bash
> #
> # yum This shell script enables the automatic use of YUM
> #
> # Author: Seth Vidal <skvidal@xxxxxxxxxxxx>
> #
> # chkconfig: - 50 01
This section tells chkconfig what runlevels to start and stop the script
> #
> # description: Enable daily run of yum, a program updater.
> # processname: yum
> # config: /etc/yum.conf
These are also used by chkconfig (I think) but tend to be good for
reference
> #
>
> # source function library
> . /etc/rc.d/init.d/functions
>
This loads the general "redhat" function libraries which give a bunch of
single line commands to make things easier and more "redhatty" such as
killing processes and starting a process with a pretty "[ OK ]" if the
startup worked.
> lockfile=/var/lock/subsys/yum
>
> RETVAL=0
>
> start() {
> echo -n $"Enabling nightly yum update: "
> touch "$lockfile" && success || failure
> RETVAL=$?
> echo
> }
This is the bit that does the actual startup - it creates a new command
called "start" that touches /var/lock/subsys/yum, this in turn probably
tells another process (possibly called from cron daily) that when it wakes
up it should do something meaningful
>
> stop() {
> echo -n $"Disabling nightly yum update: "
> rm -f "$lockfile" && success || failure
> RETVAL=$?
> echo
> }
This probably tells the same process that there is no need to do anything
meaningful
>
> restart() {
> stop
> start
> }
>
> case "$1" in
> start)
> start
> ;;
"create the lockfile that tells yum to do something when we run it daily"
> stop)
> stop
> ;;
"delete the lockfile that tells yum to do something when we run it daily"
> restart|force-reload)
> restart
> ;;
> reload)
> ;;
> condrestart)
> [ -f "$lockfile" ] && restart
> ;;
> status)
> if [ -f $lockfile ]; then
> echo $"Nightly yum update is enabled."
> RETVAL=0
> else
> echo $"Nightly yum update is disabled."
> RETVAL=3
> fi
> ;;
> *)
> echo $"Usage: $0
> {start|stop|status|restart|reload|force-reload|condrest
> art}"
> exit 1
> esac
>
> exit $RETVAL
> ***
>
> What about that script actually runs anything?
This script doesnt run anything perse, but as above, it "enables" yum such
that when another process is called it does something.
The part here you would be intested in is the structure of a start/stop
file. Then you can figure out where it "does something" and "un-does
something" and how it fits into the startup of the system (the chkconfig
stuff and the case statement) and then write your own start/stop script.
A good simple example is as follows
[quote - smartd start/stop script ]
#!/bin/bash
# ucsc-smartsuite init file for smartd
#
# description: Self Monitoring and Reporting Technology (SMART) Daemon
#
# processname: smartd
# chkconfig: - 45 45
# source function library
. /etc/rc.d/init.d/functions
case "$1" in
start)
echo -n "Starting smartd: "
daemon /usr/sbin/smartd
touch /var/lock/subsys/smartd
echo
;;
stop)
echo -n "Shutting down smartd: "
killproc smartd
rm -f /var/lock/subsys/smartd
echo
;;
restart)
$0 stop
$0 start
;;
status)
status smartd
;;
*)
echo "Usage: smartd {start|stop|restart|status}"
exit 1
esac
exit 0
[/quote]
Here we can see all the elements of a start/stop script setting up the
chkconfig entries, loading the function libs, then calling the start
section, which "does stuff" and the stop section which "un-does stuff", in
this case the "does stuff" is
1. Print a pretty message :- echo -n "Starting smartd: "
2. run the program and print the result :- daemon /usr/sbin/smartd
3. set a lock file :- touch /var/lock/subsys/smartd
4. clean up the line :- echo
the "un-does stuff" is..
1. Print a pretty message :- echo -n "Shutting down smartd: "
2. Kill the process called "smartd" :- killproc smartd
3. Remove the lockfile :- rm -f /var/lock/subsys/smartd
4. clean up the line :- echo
The chkconfig line tells us where the script should be inserted into the
startup sequence and the shutdown sequence, this is important for a number
of reasons and they depend on the program you are startting/stopping. The
line also tells us what runlevels the program needs to run at which is
also important. (no point in starting the networking daemons such as used
for e-mail and remote connection if we are running in "no networking" mode
- similarly, no point in starting the Xwindows helper apps if we are not
running Xwindows)
chkconfig stuff..
# chkconfig: - 45 45
This says "Run this command in all run levels at position 45"
some examples that would be handy are..
# chkconfig: 235 80 30
"run this at run levels 2, 3 and 5 (the common networking+multi-user
modes) at startup position 80 and shutdown position 30"
80 is sorta at the end of the start sequence and can be used for things
such as web servers that require that some other services are started
earlier (such as networking)
for things such as a web cam, you may require that
1. the system has initialised
2. The file systems are mounted
3. The networking system is running
4. A web server is running
as such you will want to start your camera after the http server has
started (check the httpd chkconfig line)
> Where can I learn more about doing what Im looking for?
HTH somewhat,
--
Steve.
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