Not update centos 7

linux-common/centos/common/update.sh

@@ -1,6 +1,15 @@
 #!/bin/bash
 
-echo "--- Executing: $0 $@"
 
-echo 'Updating OS. This will take a around 10 minutes'
-dnf -y --quiet update
+cVer=`rpm -E %{rhel}`
+if [ -z "$cVer" ]; then
+    echo "Error: Unable to determine CentOS version."
+    exit 0
+fi
+if [ "$cVer" -gt 7 ]; then
+    echo "--- Executing: $0 $@"
+
+    echo 'Updating OS. This will take a around 10 minutes'
+
+    dnf -y --quiet update
+fi