Change semantics of S and K files

Presently, there are a lot of special cases:
- runlevel 0 and 6 unconditionally run "script stop" if they
  find a Kxxscript symlink. This may lead to trying to stop an
  already stopped device if for example switching to runlevel 0/6
  from runlevel 1. This can be fixed by stating the convention
  that it is the responsability of scripts to check that the service
  is running before killing it (or not running before starting it).
  Still, we shouldn't try to stop a service if it was marked K in
  the previous runlevel. And same for S files: we shouldn't try to
  start a service that was marked S in the previous runlevel. Note
  that changing runlevel is not a "reset": if a user has manually
  changed the state of a daemon, this state will remain the same
  upon changing runlevel if the S/K status of that dameon is
  the same in both runlevels.

- Sxxscript symlinks in runlevel 0/6 are run as "script stop"
  instead of the more intuitive "script start". This does not interact
  well with LSB-tools (some scripts would need "Default-Start: S 0 6"
  but then it is impossible to get correct "Required-Start" or
  "Should-Start" fields). Furthermore, having a counter-intuitive
  behavior is error prone. So now runlevel 0/6 will run "script
  sart" for a Sxxscript.

bootscripts/lfs/init.d/rc

@@ -6,10 +6,18 @@
 #
 # Authors     : Gerard Beekmans  - gerard@linuxfromscratch.org
 #             : DJ Lucas - dj@linuxfromscratch.org
-# Update      : Bruce Dubbs - bdubbs@linuxfromscratch.org
+# Updates     : Bruce Dubbs - bdubbs@linuxfromscratch.org
+#             : Pierre Labastie - pierre@linuxfromscratch.org
 #
 # Version     : LFS 7.0
 #
+# Notes       : Updates March 24th, 2022: new semantics of S/K files
+#               - Instead of testing that S scripts were K scripts in the
+#                 previous runlevel, test that they were not S scripts
+#               - Instead of testing that K scripts were S scripts in the
+#                 previous runlevel, test that they were not K scripts
+#               - S scripts in runlevel 0 or 6 are now run with
+#                "script start" (was "script stop" previously).
 ########################################################################
 
 . /lib/lsb/init-functions
@@ -144,8 +152,9 @@ fi
 # Read the state file if it exists from runlevel S
 [ -r /run/interactive ] && source /run/interactive
 
-# Attempt to stop all services started by the previous runlevel,
-# and killed in this runlevel
+# Stop all services marked as K, except if marked as K in the previous
+# runlevel: it is the responsibility of the script to not try to kill
+# a non running service
 if [ "${previous}" != "N" ]; then
    for i in $(ls -v /etc/rc.d/rc${runlevel}.d/K* 2> /dev/null)
    do
@@ -155,20 +164,8 @@ if [ "${previous}" != "N" ]; then
          continue
       fi
 
-      suffix=${i#/etc/rc.d/rc$runlevel.d/K[0-9][0-9]}
-      prev_start=/etc/rc.d/rc$previous.d/S[0-9][0-9]$suffix
-      sysinit_start=/etc/rc.d/rcS.d/S[0-9][0-9]$suffix
-
-      if [ "${runlevel}" != "0" -a "${runlevel}" != "6" ]; then
-         if [ ! -f ${prev_start} -a  ! -f ${sysinit_start} ]; then
-            MSG="WARNING:\n\n${i} can't be "
-            MSG="${MSG}executed because it was not "
-            MSG="${MSG}not started in the previous "
-            MSG="${MSG}runlevel (${previous})."
-            log_warning_msg "$MSG"
-            continue
-         fi
-      fi
+      suffix=${i#/etc/rc.d/rc${runlevel}.d/K[0-9][0-9]}
+      [ -e /etc/rc.d/rc${previous}.d/K[0-9][0-9]$suffix ] && continue
 
       run ${i} stop
       error_value=${?}
@@ -184,31 +181,25 @@ if [ "$runlevel" == "6" -a -n "${FASTBOOT}" ]; then
 fi
 
 
-# Start all functions in this runlevel
+# Start all services marked as S in this runlevel, except if marked as
+# S in the previous runlevel
+# it is the responsabily of the script to not try to start an already running
+# service
 for i in $( ls -v /etc/rc.d/rc${runlevel}.d/S* 2> /dev/null)
 do
-   if [ "${previous}" != "N" ]; then
-      suffix=${i#/etc/rc.d/rc$runlevel.d/S[0-9][0-9]}
-      stop=/etc/rc.d/rc$runlevel.d/K[0-9][0-9]$suffix
-      prev_start=/etc/rc.d/rc$previous.d/S[0-9][0-9]$suffix
 
-      [ -f ${prev_start} -a ! -f ${stop} ] && continue
+   if [ "${previous}" != "N" ]; then
+      suffix=${i#/etc/rc.d/rc${runlevel}.d/S[0-9][0-9]}
+      [ -e /etc/rc.d/rc${previous}.d/S[0-9][0-9]$suffix ] && continue
    fi
 
    check_script_status
-      if [ "${SCRIPT_STAT}" == "1" ]; then
-         SCRIPT_STAT="0"
-         continue
-      fi
+   if [ "${SCRIPT_STAT}" == "1" ]; then
+      SCRIPT_STAT="0"
+      continue
+   fi
 
-   case ${runlevel} in
-      0|6)
-         run ${i} stop
-         ;;
-      *)
-         run ${i} start
-         ;;
-   esac
+   run ${i} start
 
    error_value=${?}