More details when the os is too old.

rtkbase_update.sh

@@ -34,7 +34,11 @@ str2str_file=$(systemctl is-active str2str_file)
 rtkrcv_raw2nmea=$(systemctl is-active rtkbase_raw2nmea)
 
 check_before_update() {
-  TOO_OLD='You'"'"'re Operating System is too old\nPlease update it or reflash you SDCard with a more recent RTKBase image\n'
+  TOO_OLD='<b>You'"'"'re Operating System is too old!</b>\n
+    Please reflash your SDCard with a more recent RTKBase image, or upgrade your OS.\n
+    Don'"'"'t forget to backup your settings.\n\n
+    <a href="https://github.com/Stefal/rtkbase" target="_blank">RTKBase repository</a>\n\n
+    <a href="https://docs.centipede.fr/docs/base/Installation.html" target="_blank">Documentation CentipedeRTK</a>'
 
   if [[ -f /etc/os-release ]]
     then