Update

netboot.sh

@@ -157,25 +157,27 @@ while [ $# -gt 0 ]; do
     shift
 done
 
-case "$DEBI_PRESET" in
-    china)
-        DEBI_NS=${DEBI_NS:-156.154.70.5 156.154.71.5}
-        DEBI_PROTOCOL=${DEBI_PROTOCOL:-https}
-        DEBI_MIRROR=${DEBI_MIRROR:-chinanet.mirrors.ustc.edu.cn}
-        DEBI_TIMEZONE=${DEBI_TIMEZONE:-Asia/Shanghai}
-        DEBI_NTP=${DEBI_NTP:-cn.ntp.org.cn}
-        DEBI_SECURITY=${DEBI_SECURITY:-true}
-        ;;
-    cloud)
-        DEBI_PROTOCOL=${DEBI_PROTOCOL:-https}
-        DEBI_MIRROR=${DEBI_MIRROR:-cdn-aws.deb.debian.org}
-        DEBI_NTP=${DEBI_NTP:-time.google.com}
-        DEBI_SECURITY=${DEBI_SECURITY:-true}
-        ;;
-    *)
-        echo_stderr "Error: No such preset $DEBI_PRESET"
-        exit 1
-esac
+if [ -n "$DEBI_PRESET" ]; then
+    case "$DEBI_PRESET" in
+        china)
+            DEBI_NS=${DEBI_NS:-156.154.70.5 156.154.71.5}
+            DEBI_PROTOCOL=${DEBI_PROTOCOL:-https}
+            DEBI_MIRROR=${DEBI_MIRROR:-chinanet.mirrors.ustc.edu.cn}
+            DEBI_TIMEZONE=${DEBI_TIMEZONE:-Asia/Shanghai}
+            DEBI_NTP=${DEBI_NTP:-cn.ntp.org.cn}
+            DEBI_SECURITY=${DEBI_SECURITY:-true}
+            ;;
+        cloud)
+            DEBI_PROTOCOL=${DEBI_PROTOCOL:-https}
+            DEBI_MIRROR=${DEBI_MIRROR:-cdn-aws.deb.debian.org}
+            DEBI_NTP=${DEBI_NTP:-time.google.com}
+            DEBI_SECURITY=${DEBI_SECURITY:-true}
+            ;;
+        *)
+            echo_stderr "Error: No such preset $DEBI_PRESET"
+            exit 1
+    esac
+fi
 
 DEBI_SUITE=${DEBI_SUITE:-stretch}
 DEBI_NEW="debian-$DEBI_SUITE"