Allow skipping the package upgrade.

setup/pi/setup-teslausb

@@ -5,6 +5,7 @@ BRANCH=${BRANCH:-master}
 HEADLESS_SETUP=${HEADLESS_SETUP:-false}
 USE_LED_FOR_SETUP_PROGRESS=true
 CONFIGURE_ARCHIVING=${CONFIGURE_ARCHIVING:-true}
+UPGRADE_PACKAGES=${UPGRADE_PACKAGES:-true}
 
 function setup_progress () {
   local setup_logfile=/boot/teslausb-headless-setup.log
@@ -197,8 +198,13 @@ function update_package_index () {
 }
 
 function upgrade_packages () {
-  setup_progress "Upgrading installed packages..."
-  apt-get --assume-yes upgrade
+  if [ "$UPGRADE_PACKAGES" = true ]
+  then
+    setup_progress "Upgrading installed packages..."
+    apt-get --assume-yes upgrade
+  else
+    setup_progress "Skipping package upgrade."
+  fi
 }
 
 export -f setup_progress