diff --git a/xCAT-server/share/xcat/install/ubuntu/compute.tmpl b/xCAT-server/share/xcat/install/ubuntu/compute.tmpl
old mode 100644
new mode 100755
index d3b3a79c8..01c1c74ac
--- a/xCAT-server/share/xcat/install/ubuntu/compute.tmpl
+++ b/xCAT-server/share/xcat/install/ubuntu/compute.tmpl
@@ -53,7 +53,7 @@ d-i partman/early_command string \
         rm /tmp/devs-with-boot 2>/dev/null || true; \
     else \
         DEV=`ls /dev/disk/by-path/* -l | egrep -o '/dev.*sd[^0-9]$' | sort -t : -k 1 -k 2 -k 3 -k 4 -k 5 -k 6 -k 7 -k 8 -g | head -n1 | egrep -o 'sd.*$'`; \
-        if [[ $DEV == "" ]]; then DEV="sda"; fi; \
+        if [[ "$DEV" == "" ]]; then DEV="sda"; fi; \
         echo "/dev/$DEV" > /tmp/boot_disk; \
     fi; \
     debconf-set partman-auto/disk "$(cat /tmp/boot_disk)"