grub output over serial console

admin-guide/troubleshooting/boot.md

@@ -24,3 +24,15 @@ The serial port should then be connected to a file on the datastore `serial_cons
 
 These files then can be accessed over `lxsup00.psi.ch:/data/serial_console`.
 
+## Send Grub Output to Serial Port
+
+For sending out Grub debug information over the serial port to a file because it is to much to fit the screen or for later inspection, you might do the following:
+- in the Grub menue type `c` to get to the command line
+- configure the serial port with
+```
+serial --unit=0 --speed=115200
+```
+- set the output to the serial port, run the debug command and set the output back:
+```
+terminal_output serial; lsefi; terminal_output console
+```