diff --git a/xCAT/postscripts/ospkgs b/xCAT/postscripts/ospkgs
index 1942dcc87..bfdb78179 100755
--- a/xCAT/postscripts/ospkgs
+++ b/xCAT/postscripts/ospkgs
@@ -660,7 +660,7 @@ elif ( pmatch "$OSVER" "sles11*" ); then
     fi
 elif ( pmatch "$OSVER" "ubuntu*" ); then
 	# verify dpkg is installed
-	result=`which dpkg`
+	result=`dpkg --version`
 	if [ $? -ne 0 ]; then
 		echo "Please install dpkg on $NODE."
 		exit 1
diff --git a/xCAT/postscripts/otherpkgs b/xCAT/postscripts/otherpkgs
index 485e09ca8..c6b8e57a6 100755
--- a/xCAT/postscripts/otherpkgs
+++ b/xCAT/postscripts/otherpkgs
@@ -272,7 +272,7 @@ hasdpkg=0
 supdatecommand="rpm -Uvh --replacepkgs"
 sremovecommand="rpm -ev"
 
-result=`which rpm`
+result=`rpm --version`
 if [ $? -eq 0 ]; then
     hasrpm=1
     result=`rpm -q yum`
@@ -285,7 +285,7 @@ if [ $? -eq 0 ]; then
         fi
     fi 
 else
-    result=`which dpkg`
+    result=`dpkg --version`
     if [ $? -eq 0 ]; then
         hasdpkg=1
 	supdatecommand="dpkg -i"