Init.d for application that doesn't detach from terminal?

littlebigman · 01-14-2014, 10:35 AM

Hello

Title says it all: In Debian, I need to find a way to launch an application at boot time that doesn't normally run daemonized.

Here's what it looks like in Ubuntu:

Code:

description "My non-daemon app"
start on stopped rc
stop on runlevel [016]
respawn
script
/usr/bin/myapp -document_root /var/www
end script
post-stop exec sleep 3

I tried using an existent init.d script and just adding a trailing "&" on the relevant line in the "start" section, but it doesn't look right: Unlike other daemons, "ps aux" show both the application and the init.d script:

Code:

#! /bin/sh
### BEGIN INIT INFO
# Provides:          myapp
# Required-Start:    $syslog $time $remote_fs
# Required-Stop:     $syslog $time $remote_fs
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: My app
# Description:       Debian init script for my app
### END INIT INFO

PATH=/bin:/usr/bin:/sbin:/usr/sbin
DAEMON=/usr/sbin/myapp
PIDFILE=/var/run/myapp.pid

test -x $DAEMON || exit 0

. /lib/lsb/init-functions

case "$1" in
  start)
        log_daemon_msg "Starting My app" "myapp"
        start_daemon -p $PIDFILE $DAEMON &
        log_end_msg $?
    ;;
  stop)
        log_daemon_msg "Stopping Myapp" "myapp"
        killproc -p $PIDFILE $DAEMON
        log_end_msg $?
    ;;
  force-reload|restart)
    $0 stop
    $0 start
    ;;
  status)
    status_of_proc -p $PIDFILE $DAEMON atd && exit 0 || exit $?
    ;;
  *)
    echo "Usage: /etc/init.d/myapp {start|stop|restart|force-reload|status}"
    exit 1
    ;;
esac

exit 0

Is there a correct way to write an init.d script so that the app is launched with the rest of them?

Thank you.

anomie · 01-14-2014, 01:52 PM

As you probably know, the exec command (bash builtin) will allow the child process to take over the PID from its parent (i.e. per the manpages, the command specified "replaces the shell").

For a rather different approach, you can run your command (even from an init script) in batch using the at(1) daemon, a la:

Code:

at now <<< '/your/non-daemon-script/here'

littlebigman · 01-15-2014, 07:52 AM

Thanks. What would be the right way to edit the init.d script and use "exec" instead of "&" to launch the application?

anomie · 01-15-2014, 09:46 AM

I just ran through a contrived experiment that (I think) will produce the effect you're looking for.

run-it.bash

Code:

#!/bin/bash

PATH=/usr/bin:/bin

# Note: use the FQ path here; my test
# makes assumptions about cwd.
#
exec ./test.bash &

exit 0

test.bash

Code:

#!/bin/bash

PATH=/usr/bin:/bin

touch /tmp/first-touch

sleep 120

touch /tmp/second-touch

exit 0

Execution and results:

Code:

[hk] ~> ./run-it.bash

[hk] ~> ps -ef | grep -E '[t]est\.bash|[r]un-it\.bash'
eriks    18005     1  0 09:43 pts/5    00:00:00 /bin/bash /home/eriks/test.bash

[hk] ~> ls -l /tmp/first-touch /tmp/second-touch
-rw-r--r-- 1 eriks eriks 0 Jan 15 09:43 /tmp/first-touch
-rw-r--r-- 1 eriks eriks 0 Jan 15 09:45 /tmp/second-touch