diff --git a/xCAT/postscripts/ospkgs b/xCAT/postscripts/ospkgs
index 1ea079ec0..3f799621b 100755
--- a/xCAT/postscripts/ospkgs
+++ b/xCAT/postscripts/ospkgs
@@ -1,6 +1,5 @@
 #!/bin/bash  
 # IBM(c) 2010 EPL license http://www.eclipse.org/legal/epl-v10.html
-
 #-------------------------------------------------------------------------------
 #=head1  ospkgs
 #=head2  Used on Linux only. It installs/updates the rpms thta are from OS distro. 
@@ -225,86 +224,90 @@ if [ "$KERNELDIR" != "" ]; then
     OSPKGDIR="$OSPKGDIR,$KERNELDIR"
 fi 
 
-    OIFS=$IFS
-    IFS=$','
-    if ( pmatch "$OSVER" "ubuntu*" ); then
-        IFS=$(printf ',')
+OIFS=$IFS
+IFS=$','
+if ( pmatch "$OSVER" "ubuntu*" ); then
+    IFS=$(printf ',')
+fi
+
+array_ospkgdirs=($OSPKGDIR)   
+
+#initialize the array "os_path" with all the valid repository paths 
+#under the directories specified in "OSPKGDIR"
+
+array_empty os_path
+index=0
+for dir in  ${array_ospkgdirs[@]}  
+do
+     
+    default_pkgdir="$INSTALLDIR/$OSVER/$ARCH"
+    OSPKGDIR="$OSPKGDIR" 
+    if [ $mounted -eq 0 ]; then
+        #OSPKGDIR="$OSPKGDIR" 
+        ospkgdir="$NFSSERVER$dir"
+    else 
+        ospkgdir="$dir"
     fi
-
-    array_ospkgdirs=($OSPKGDIR)   
-    IFS=$OIFS
-    array_empty os_path
-    index=0
-    for dir in  ${array_ospkgdirs[@]}  
-    do
-         
-        default_pkgdir="$INSTALLDIR/$OSVER/$ARCH"
-        OSPKGDIR="$OSPKGDIR" 
-        if [ $mounted -eq 0 ]; then
-            #OSPKGDIR="$OSPKGDIR" 
-            ospkgdir="$NFSSERVER$dir"
-        else 
-            ospkgdir="$dir"
+    
+    # for the os base pkg dir(default_pkgdir) , there are some special cases.
+    # (1)for rhels6, there is one repodata in the os base dir; so keep it here, and handle the other cases below
+    # (2)for sles, we should specified the baseurl should be ./install/sles11/ppc64/1
+    # (3)for SL5, we should append the /SL
+    # (4) for other os, we just keep it here.
+    # For other pkg paths, we just keep it here.
+    if [ $dir == $default_pkgdir ] || [ $dir == "$default_pkgdir/" ]; then
+        if ( pmatch "$OSVER" "sles*" ); then
+            OSPKGDIR="$OSPKGDIR/1"
+            ospkgdir="$ospkgdir/1"
+        elif ( pmatch "$OSVER" "SL5*" ); then
+            OSPKGDIR="$OSPKGDIR/SL"
+            ospkgdir="$ospkgdir/SL"
         fi
-        
-        # for the os base pkg dir(default_pkgdir) , there are some special cases.
-        # (1)for rhels6, there is one repodata in the os base dir; so keep it here, and handle the other cases below
-        # (2)for sles, we should specified the baseurl should be ./install/sles11/ppc64/1
-        # (3)for SL5, we should append the /SL
-        # (4) for other os, we just keep it here.
-        # For other pkg paths, we just keep it here.
+    fi
+    array_set_element os_path $index $ospkgdir
+     
+    if ( pmatch "$OSVER" "rhel*" ); then
+        #default_pkgdir="$INSTALLDIR/$OSVER/$ARCH"
         if [ $dir == $default_pkgdir ] || [ $dir == "$default_pkgdir/" ]; then
-            if ( pmatch "$OSVER" "sles*" ); then
-                OSPKGDIR="$OSPKGDIR/1"
-                ospkgdir="$ospkgdir/1"
-            elif ( pmatch "$OSVER" "SL5*" ); then
-                OSPKGDIR="$OSPKGDIR/SL"
-                ospkgdir="$ospkgdir/SL"
-            fi
-        fi
-        array_set_element os_path $index $ospkgdir
-         
-        if ( pmatch "$OSVER" "rhel*" ); then
-            #default_pkgdir="$INSTALLDIR/$OSVER/$ARCH"
-            if [ $dir == $default_pkgdir ] || [ $dir == "$default_pkgdir/" ]; then
-          
-                if ( pmatch "$OSVER" "rhels6*" ); then
-                   if [ $ARCH == "ppc64" ]; then
-                       ospkgdir_ok="$ospkgdir/Server"
-                       index=$(expr $index + 1)          
-                       array_set_element os_path $index $ospkgdir_ok
-                   fi               
- 
-                   if [ $ARCH == "x86_64" ]; then
-                        for arg in "Server" "ScalableFileSystem" "HighAvailability" "ResilientStorage" "LoadBalancer" 
-                        do
-                            ospkgdir_ok="$ospkgdir/$arg"
-                            index=$(expr $index + 1)          
-                            array_set_element os_path $index $ospkgdir_ok
-                        done
-                    fi               
+      
+            if ( pmatch "$OSVER" "rhels6*" ); then
+               if [ $ARCH == "ppc64" ]; then
+                   ospkgdir_ok="$ospkgdir/Server"
+                   index=$(expr $index + 1)          
+                   array_set_element os_path $index $ospkgdir_ok
+               fi               
 
-                elif ( pmatch "$OSVER" "rhels5*" ); then
-                     # for rhels5, the repodata is in ./Server, ./Cluster, ./CusterStorage, not in ./
-                     ospkgdir_ok="$ospkgdir/Server"
-                     array_set_element os_path $index $ospkgdir_ok
-               
-                     if [ $ARCH == "x86_64" ]; then
-                         for arg in "Cluster" "ClusterStorage"
-                         do
-                             ospkgdir_ok="$ospkgdir/$arg"
-                             index=$(expr $index + 1)          
-                             array_set_element os_path $index $ospkgdir_ok
-                         done
-                     fi   # x86_64
-                fi # if...elif..fi
-             fi  # eq default_pkgdir
-          fi    # match rhel*
+               if [ $ARCH == "x86_64" ]; then
+                    for arg in "Server" "ScalableFileSystem" "HighAvailability" "ResilientStorage" "LoadBalancer" 
+                    do
+                        ospkgdir_ok="$ospkgdir/$arg"
+                        index=$(expr $index + 1)          
+                        array_set_element os_path $index $ospkgdir_ok
+                    done
+                fi               
 
-          index=$(expr $index + 1)          
-            
-   done    
+            elif ( pmatch "$OSVER" "rhels5*" ); then
+                 # for rhels5, the repodata is in ./Server, ./Cluster, ./CusterStorage, not in ./
+                 ospkgdir_ok="$ospkgdir/Server"
+                 array_set_element os_path $index $ospkgdir_ok
+           
+                 if [ $ARCH == "x86_64" ]; then
+                     for arg in "Cluster" "ClusterStorage"
+                     do
+                         ospkgdir_ok="$ospkgdir/$arg"
+                         index=$(expr $index + 1)          
+                         array_set_element os_path $index $ospkgdir_ok
+                     done
+                 fi   # x86_64
+            fi # if...elif..fi
+         fi  # eq default_pkgdir
+      fi    # match rhel*
 
+      index=$(expr $index + 1)          
+        
+done    
+
+IFS=$OIFS
  
 
 
@@ -334,6 +337,7 @@ fi
 
 pkgs=''  #packages
 groups=''   #groups
+groups_d=''   #groups to remove
 pkgs_d=''   #packages to remove
 cudapkgs='' #cuda pkg set
 
@@ -343,39 +347,57 @@ if ( pmatch "$OSVER" "ubuntu*" ); then
     IFS=$(printf ',')
 fi
 pkgarray=($OSPKGS)
-IFS=$OIFS
 
+#parse the pkglist file, categorize the pkglist entries according to 
+#the type(package/group/patterns) and action(install/remove)
 for x in ${pkgarray[@]};
 do
+    #a flag indication the operation to current pkg/group
+    # 0:install;1:remove
+    remove=0
+
     #remove leading and trailing spaces
     x=`echo $x |sed 's/^ *//;s/ *$//'`
     #echo "x=$x"
     pos=`expr index  "$x" -`
     if [ $pos -eq 1 ]; then 
-	pkgs_d="$pkgs_d ${x#-}"
-    else
-	pos=`expr index  "$x" @`
-	if [ $pos -eq 1 ]; then 
-	    #remove leading @
-	    tmp=${x#@}
-            #remove leading and trailing spaces
-	    tmp=`echo $tmp |sed 's/^ *//;s/ *$//'`
-            #if there are spaces in the middle of the name, quote it
-	    pos=`expr index "$tmp" "\ "`
-	    if [ $pos -gt 0  ]; then
-		groups="$groups \"$tmp\""
-	    else
-		groups="$groups $tmp"
-	    fi
-	else
-            if ( pmatch  "$x" "cuda*" ); then
-                cudapkgs="$cudapkgs $x" 
-            else
-                pkgs="$pkgs $x"
-            fi
-	fi
+       remove=1
+       x=${x#-}
     fi
+
+    pos=`expr index  "$x" @`
+    if [ $pos -eq 1 ]; then 
+        #remove leading @
+        tmp=${x#@}
+        #remove leading and trailing spaces
+        tmp=`echo $tmp |sed 's/^ *//;s/ *$//'`
+        #if there are spaces in the middle of the name, quote it
+        pos=`expr index "$tmp" "\ "`
+        if [ $pos -gt 0  ]; then
+           tmp="\"$tmp\""
+        fi
+        
+        #categorize the groups according to the action(install/remove)
+        if [ $remove -eq 0 ]; then
+    	   groups="$groups $tmp"
+        else
+           groups_d="$groups_d $tmp"
+        fi
+    else
+        if ( pmatch  "$x" "cuda*" ); then
+            cudapkgs="$cudapkgs $x" 
+        else
+            #categorize the packages according to the action(install/remove)
+            if [ $remove -eq 0 ]; then
+               pkgs="$pkgs $x"
+            else
+               pkgs_d="$pkgs_d $x"
+            fi
+        fi
+    fi
+
 done
+IFS=$OIFS
 
 if [ $debug -ne 0 ]; then
     echo "pkgs=$pkgs"
@@ -383,9 +405,18 @@ if [ $debug -ne 0 ]; then
         echo "cudapkgs=$cudapkgs"
     fi
     echo "groups=$groups"
+    echo "remove groups=$groups_d"
     echo "remove pkgs=$pkgs_d"
 fi
 
+#perform the software maintenance with the available package management tools, the process:
+#1.make sure the necessary package management tool is available 
+#2.enable all the available repositories and refresh the relevant metadata
+#3.upgrade all the existing packages
+#4.install specified package groups if any
+#5.install specified packages if any
+#6.remove specified package groups if any
+#7.remove specified packages if any
 if ( pmatch "$OSVER" "sles10*" ); then
     #check if rug is installed
     result=`rpm -q rug`
@@ -643,6 +674,26 @@ elif ( pmatch "$OSVER" "sles*" ); then
 	fi
     fi
 
+
+    
+    #remove  patterns if any
+    if [ -n "$groups_d" ]; then
+	cmd="$ENVLIST zypper remove -y  -t pattern $groups_d"
+	result=`eval $cmd 2>&1`
+        R=$?
+        if [ $R -ne 0 ]; then
+            RETURNVAL=$R
+	    logger -t xcat -p local4.info "ospkgs: $cmd\n    $result"
+	    echo "ospkgs: $cmd"
+	    echo $result
+	else
+	    if [ $debug -ne 0 ]; then
+		echo "ospkgs: $cmd"
+		echo $result
+	    fi
+	fi
+    fi
+
     #remove some packages if specified
     if [ -n "$pkgs_d" ]; then
 	cmd="$ENVLIST zypper remove -y $pkgs_d"
@@ -728,6 +779,9 @@ elif ( pmatch "$OSVER" "ubuntu*" ); then
                    RETURNVAL=$R
                 fi
 	fi
+  
+        #remove package group is not supported in ubuntu, 
+        #cause there is no  rpm-like "groups" supported by dpkg/apt
 
 	# install packages
 	if [ -n "$pkgs" ]; then
@@ -833,7 +887,8 @@ else
 
     #install new groups if any
     if [ -n "$groups" ]; then
-	cmd="echo $groups| $ENVLIST xargs yum -y groupinstall"
+	#cmd="echo $groups| $ENVLIST xargs yum -y groupinstall"
+	cmd="$ENVLIST yum -y groupinstall $groups"
 	result=`eval $cmd 2>&1`
         R=$?
         if [ $R -ne 0 ]; then
@@ -867,6 +922,24 @@ else
 	fi
     fi
 
+    #remove some groups if specified
+    if [ -n "$groups_d" ]; then
+        cmd="$ENVLIST yum -y groupremove $groups_d"
+        result=`eval $cmd 2>&1`
+        R=$?
+        if [ $R -ne 0 ]; then
+           RETURNVAL=$R
+            logger -t xcat -p local4.info "ospkgs: $cmd\n    $result"
+            echo "ospkgs: $cmd"
+            echo $result
+        else
+            if [ $debug -ne 0 ]; then
+                echo "ospkgs: $cmd"
+                echo $result
+            fi
+        fi
+    fi
+
     #remove some rpms if specified
     if [ -n "$pkgs_d" ]; then
 	cmd="$ENVLIST yum -y remove $pkgs_d"