lipnsa hook: better parameter handling

still not optimal, e.g. the help message cannot be printed without
preceded warnings.

initrd_hooks/lipnsa.hook.sh

@@ -3,15 +3,25 @@
 # Lars Beckers, larsb@fsmpi.rwth-aachen.de, September 2014
 
 LIPSTICK="/root/cdrom"
-if [ -n "$1" ] && [ ! "$1" == "--help" ]; then
+LOGFUNCTIONSSOURCE="/scripts/casper-functions"
+TARGET="/root"
+
+if [ -e "${LOGFUNCTIONSSOURCE}" ]; then
+  source ${LOGFUNCTIONSSOURCE}
+else
+  echo "Warning: ${LOGFUNCTIONSSOURCE} does not exist. Cannot source casper functions!"
+fi
+
+if [ -n "$1" ] && [ -d "$1" ]; then
   LIPSTICK="$1"
+  shift
+else
+  log_warning_msg "LIPSTICK mount point not specified. Falling back to ${LIPSTICK}."
 fi
 
 LIPSTATS="${LIPSTICK}/lipstats"
-TARGET="/root"
-LOGFUNCTIONSSOURCE="/scripts/casper-functions"
 
-if [ "$1" == "--help" ]; then
+if [ $# -gt 0 ]; then
 	echo "collects system information, i.e. hardware and what the kernel thinks about it"
 	echo "called as liphook before leaving initramfs"
 	echo "usage: lipnsa.sh"
@@ -41,8 +51,6 @@ if [ "$1" == "--help" ]; then
 	exit
 fi
 
-source ${LOGFUNCTIONSSOURCE}
-
 if [ -f /proc/cmdline ]; then
 	grep fnord /proc/cmdline
 	if [ $? == 0 ]; then