Ubuntu - Fix “No Video Signal” Issue on Emu/Roadrunner

2018
Computer Servicing
Author

Sam White

Published

July 5, 2018

Both Apple Xserves (Emu/Roadrunner) running Ubuntu (16.04LTS) experienced the same issue - the monitor would indicate “No Video Signal”, would go dark, and wasn’t responsive to keyboard/mouse movements. However, you could ssh into both machines w/o issue.

Although having these machines be “headless” (i.e. with no display) is usually fine, it’s not ideal for a couple of reasons:

  1. Difficult to use for other lab members who aren’t as familiar with SSH - specifically if they would want to use a Jupyter Notebook remotely (this would require setting up a tunnel to their own computer).

  2. Can’t use Remmina Remote Desktop until a user has physically logged in from the Ubuntu login screen at least once, in order to launch Remmina.

The second aspect was the major impetus in me finally being motivated to deal with this. Accessing these computers via remote desktop is much easier to manage long-running Jupyter Notebooks instead of relying on an SSH tunnel. The tunnel greatly limits my access to the Jupyter Notebook outside of the computer that has the tunnel set up.

Well, this led me down a horrible rabbit hole of Linux stuff that I won’t get fully in to (particularly, since I didn’t understand most of it and can’t remember all the crazy stuff I read/tried).

However, here’s the gist:

  1. Needed to edit /etc/default/grub

  2. After editing, needed to update grub config file: sudo update-grub

Despite the fact that both machines are (or, should be) identical, I did not get the same results. The edits I made to the /etc/default/grub file on Emu worked immediately. The edits were:

  1. Add nomodeset to this (this is the edited line) line (this seemed to be the most common suggestion for fixing the “No Video Signal” issue):

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"

  1. Comment out this line (this line was triggering an error/warning about writing the config file when running the update-grub command):

#GRUB_HIDDEN_TIMEOUT=0

For some reason, Roadrunner did not take kindly to those changes and it took a long time to resolve, ending with changing permissions on ~/.Xauthority back to their original permissions (they got altered when I ran some command - sudo startx or something) to get out of a login loop.

Regardless, both are fixed, both can be used when physically sitting at the computer, and both can be accessed remotely using Remmina!