lfs-book/chapter07/rc.xml

<sect1 id="ch07-rc">
<title>Creating the rc script</title>

<para>The first main boot script is the <filename>/etc/init.d/rc</filename> 
script. Create the <filename>/etc/init.d/rc</filename> script by running the
following command:</para>

<para><screen><userinput>cat &gt; /etc/init.d/rc &lt;&lt; "EOF"</userinput>
#!/bin/sh
# Begin /etc/init.d/rc
#
# By Jason Pearce  - jason.pearce@linux.org
# Modified by Gerard Beekmans - gerard@linuxfromscratch.org
# print_error_msg based on ideas by Simon Perreault -
# nomis80@videotron.ca
#

#
# Include the functions declared in the /etc/init.d/functions file
#

source /etc/init.d/functions

#
# The print_error_msg function prints an error message when an unforeseen
# error occurred that wasn't trapped for some reason by a evaluate_retval
# call or error checking in different ways.

print_error_msg()
{

        echo
        $FAILURE
        echo -n "You should not read this error message. It means "
        echo "that an unforeseen error "
        echo -n "took place and subscript $i exited with "
        echo "a return value "
        echo -n "of $error_value for an unknown reason. If you're able "
        echo "to trace this error down "
        echo -n "to a bug in one of the files provided by this book, "
        echo "please be so kind to "
        echo -n "inform us at lfs-dev@linuxfromscratch.org"
        $NORMAL
        echo
        echo
        echo "Press a key to continue..."
        read

}

#
# If you uncomment the debug variable below none of the scripts will be
# executed, just the script name and parameters will be echo'ed to the
# screen so you can see how the scripts are called by rc.
#

# Un-comment the following for debugging.
# debug=echo

#
# Start script or program.
# 
startup() {

        $debug "$@"

}   

#
# Ignore CTRL-C only in this shell, so we can interrupt subprocesses.
#

trap ":" INT QUIT TSTP

#
# Now find out what the current and what the previous runlevel are. The
# $RUNLEVEL variable is set by init for all it's children. This script
# runs as a child of init.
#

runlevel=$RUNLEVEL

#
# Get first argument. Set new runlevel to this argument. If no runlevel
# was passed to this script we won't change runlevels.
#

[ "$1" != "" ] &amp;&amp; runlevel=$1
if [ "$runlevel" = "" ]
then
        echo "Usage: $0 &lt;runlevel&gt;" &gt;&amp;2
        exit 1
fi

#
# The same goes for $PREVLEVEL (see above for $RUNLEVEL). previous will
# be set to the previous run level. If $PREVLEVEL is not set it means
# that there is no previous runlevel and we'll set previous to N.
#

previous=$PREVLEVEL
[ "$previous" = "" ] &amp;&amp; previous=N

export runlevel previous

#
# Is there an rc directory for the new runlevel?
#

if [ -d /etc/rc$runlevel.d ]

then

#
# If so, first collect all the K* scripts in the new run level.
#

        if [ $previous != N ]
        then
                for i in /etc/rc$runlevel.d/K*
                do
                [ ! -f $i ] &amp;&amp; continue

#
# the suffix variable will contain the script name without the leading
# Kxxx
#

                        suffix=${i#/etc/rc$runlevel.d/K[0-9][0-9][0-9]}
#
# If there is a start script for this K script in the previous runlevel
# determine what it's full path is
#
            previous_start=/etc/rc$previous.d/S[0-9][0-9][0-9]$suffix
#
# If there was no previous run level it could be that something was
# started in rcS.d (sysinit level) so we'll determine the path for that
# possibility as well.
#

                        sysinit_start=/etc/rcS.d/S[0-9][0-9][0-9]$suffix

#
# Stop the service if there is a start script in the previous run level 
# or in the sysinit level. If previous_start or sysinit_start do not 
# exist the 'continue' command is run which causes the script to abort
# this iteration of the for loop and continue with the next iteration.
# This boils down to that it won't run the commands after the next two
# lines and start over from the top of this for loop. See man bash for
# more info on this.
#

                        [ ! -f $previous_start ] &amp;&amp;
                        [ ! -f $sysinit_start ] &amp;&amp; continue

#
# If we found previous_start or sysinit_start, run the K script
#

                        startup $i stop
                        error_value=$?
#
# If the return value of the script is not 0, something went wrong with
# error checking inside the script. the print_error_msg function will be
# called and the message plus the return value of the K script will be
# printed to the screen
#

                        if [ $error_value != 0 ]
                        then
                                print_error_msg 
                        fi

                done
        fi

#
# Now run the START scripts for this runlevel.
#

        for i in /etc/rc$runlevel.d/S*
        do
                [ ! -f $i ] &amp;&amp; continue

                if [ $previous != N ]
        then
#
# Find start script in previous runlevel and stop script in this
# runlevel.
#

                        suffix=${i#/etc/rc$runlevel.d/S[0-9][0-9][0-9]}
                        stop=/etc/rc$runlevel.d/K[0-9][0-9][0-9]$suffix
                previous_start=/etc/rc$previous.d/S[0-9][0-9][0-9]$suffix
#
# If there is a start script in the previous level and no stop script in 
# this level, we don't have to re-start the service; abort this
# iteration and start the next one.
#

                        [ -f $previous_start ] &amp;&amp; [ ! -f $stop ] &amp;&amp; 
                        continue
                fi

                case "$runlevel" in
                        0|6)

#
# levels 0 and 6 are halt and reboot levels. We don't really start
# anything here so we call with the 'stop' parameter
#

                                startup $i stop
                                error_value=$?
#
# If the return value of the script is not 0, something went wrong with
# error checking inside the script. the print_error_msg function will be
# called and the message plus the return value of the K script will be
# printed to the screen
#

                                if [ $error_value != 0 ]
                                then
                                        print_error_msg
                                fi
                                ;;
                        *)
                                startup $i start
                                error_value=$?
#
# If the return value of the script is not 0, something went wrong with
# error checking inside the script. the print_error_msg function will be
# called and the message plus the return value of the K script will be
# printed to the screen
#

                                if [ $error_value != 0 ]
                                then
                                        print_error_msg
                                fi
                                ;;
                esac
        done
fi

# End /etc/init.d/rc
<userinput>EOF</userinput></screen></para>

</sect1>