Changed to reboot detection. Will cache last seen uptime and detect r…

…eboot when current uptime is lower than the cached uptime

agents/plugins/yum

@@ -10,6 +10,7 @@ UPDATES=0
 SECURITY_UPDATES=0
 CACHE_RESULT_CHECK=$MK_VARDIR/cache/yum_result.cache
 CACHE_YUM_UPDATE=$MK_VARDIR/cache/yum_update.cache
+CACHE_PREV_UPTIME=$MK_VARDIR/cache/yum_uptime.cache
 LAST_UPDATE_TIMESTAMP=-1
 
 
@@ -44,8 +45,25 @@ fi
 # check if system has rebooted - if so, remove cached check file to avoid wrong "reboot required"-state
 RUNNING_SECS=$(cat /proc/uptime | cut -d" " -f1 | cut -d"." -f1)
 
-# assume 120 seconds for reboot being enough
-if (( RUNNING_SECS < 120 ))
+# check if cache file with previously seen uptime is existing - create one otherwise
+if [ ! -e $CACHE_PREV_UPTIME ]
+then
+    echo 0 > $CACHE_PREV_UPTIME
+    PREV_UPTIME=0
+elif [ ! -f $CACHE_PREV_UPTIME ] || [ -L $CACHE_PREV_UPTIME ]
+then
+    # something is wrong here...
+    echo "invalid cache file"
+    exit 2
+else
+    # get cached information
+    PREV_UPTIME=$(cat "$CACHE_PREV_UPTIME")
+    # save current uptime
+    echo $RUNNING_SECS > $CACHE_PREV_UPTIME
+fi
+
+# check if current uptime is lower than cached last seen uptime to detect reboot
+if (( RUNNING_SECS < PREV_UPTIME ))
 then
     # remove pre-reboot cache which requires reboot
     rm -f $CACHE_RESULT_CHECK