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I have compiled a custom linux kernel in BusyBox. BusyBox init does not support runlevels. When the kernel boots up in BusyBox, it first executes init which looks for the specified runlevel in /etc/inittab. BusyBox init works just fine without /etc/inittab. When no inittab is found it has the following behavior:

::sysinit:/etc/init.d/rcS

This part is very clear to me, but I would like to know how to manage daemons that start up networking, create serial ports, or start java processes. I have looked in the scripts that reside in /etc/init.d/ but I don't understand how to manage them. I am looking for a good tutorial or solution to control these services myself without an automated tool like buildroot. I want to understand how these scripts work and how to create devices in /dev/ (right now I only have console and ttyAM0).

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1 Answer 1

For buildroot all your scripts must be placed in $path_to_buildroot/output/target/etc/init.d before build image. In my case this directory contains rcS and few scripts named S[0-99]script_name. So you can create your own start\stop script.

rcS:

    #!/bin/sh

    # Start all init scripts in /etc/init.d
    # executing them in numerical order.
    #
    for i in /etc/init.d/S??* ;do

         # Ignore dangling symlinks (if any).
         [ ! -f "$i" ] && continue

         case "$i" in
        *.sh)
            # Source shell script for speed.
            (
            trap - INT QUIT TSTP
            set start
            . $i
            )
            ;;
        *)
            # No sh extension, so fork subprocess.
            $i start
            ;;
        esac
    done

and for example S40network:

#!/bin/sh
#
# Start the network....
#

case "$1" in
  start)
    echo "Starting network..."
    /sbin/ifup -a
    ;;
  stop)
    echo -n "Stopping network..."
    /sbin/ifdown -a
    ;;
  restart|reload)
    "$0" stop
    "$0" start
    ;;
  *)
    echo $"Usage: $0 {start|stop|restart}"
    exit 1
esac

exit $?
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