Automatically launch your application

You've just developed a state of the art application and want it to be launched each time you boot your APF ? Then this small tutorial is for you !

System startup

First, a small remainder: when you start your board, here is how all things are started:

1. U-Boot initializes the processor, vital peripherals and then load Linux image from Flash,
2. U-Boot starts Linux image by passing it some parameters, the bootargs,
3. Linux starts, mounts its rootfs and launches /sbin/init,
4. init process checks its /etc/inittab config file and executes the instructions it contains,
5. this config file generally asks init to launch /etc/init.d/rcS at some point,
6. /etc/init.d/rcS look at all scripts in /etc/init.d/ directory which start with a S, and executes them in ascending order

Adding your own application in the system start process

• creates a shell script in /etc/init.d/:

 # touch /etc/init.d/S99app
 # chmod a+x /etc/init.d/S99app

• edit it

 # vi /etc/init.d/S99app

• put in it the following content (replace /usr/bin/your_app with your application name & path):

#!/bin/sh

# Loading the modules needed by my app:
modprobe xxxxx
 
# Launching my app:
/usr/bin/your_app &          # <-- Don't forget the "&" otherwise other system stuff won't start until you leave your app !!!

exit 0

• save your changes and !! Test it !!

# /etc/init.d/S99app

• That's it ! You can now reboot:

# sync
# reboot

Launching an application only on user login

• you may also prefer to launch your application only when a given user has logged in.
• indeed, after init has launched all the startup scripts, it generally gives the hand to getty and login tools that allow a user to login on the serial console or any other terminal.
• create a user account (here user test) and assign it a password:

$ adduser test
Changing password for test
New password: 
Retype password: 
Password for test changed by root

• leave root and log in as the new user:

$ exit
Welcome to the Armadeus development environment.
armadeus login: test
Password:
$ id
uid=1001(test) gid=1001(test) groups=1001(test)

• /home/test/ directory was automatically created. Add the instructions to execute in the /home/test/.profile file:

$ cat > /home/test/.profile <<EOF
echo "You just logged in !!"
EOF

Links

• How to customize your boot Logo