While waiting on dinner at the restaurant tonight, I noticed on my phone’s mail app (K-9 Mail) that my emails weren’t being filtered like they should. Automated notifications that normally would be Marked as Read by one of the many rules I have in Thunderbird were going unmodified.
That’s when I remembered that, an hour before, I closed Thunderbird on my Ubuntu desktop to free up some memory before launching it again. What I failed to do was launch it again.
So here I am with my usual ever-present safety net no longer present. How to fix this?
Well, duh, the answer isn’t simple until I see the answer. Then it’s a forehead-smacking “DUH” moment.
On my phone, I open JuiceSSH and click the SSH profile that logs into my home’s workstation.
From the shell, if I try to run nohup thunderbird & what I’ll get is a notice that it can’t connect to my display and it exits. Well, that’s because I don’t have JuiceSSH doing any X forwarding, so the environment variable $DISPLAY is unset.
nohuplaunches its argument in such a way that prevents the subcommand from dying once the ssh TTY connection exits (it takes the typical IO streamsstdin,stdout, andstderrand redirects the output streams tonohup.login the local folder).
The fix to the display issue is to simply say your display is the display of the running X process. In most cases, that’ll be :0.0 (it’ll be different if there are multiple users logged into the GUI or whatever; use system tools to find the one currently running).
export DISPLAY=:0.0 && nohup thunderbird &
That’s it. That adds the display variable to the environment and tells nohup to run thunderbird, which will pick up the DISPLAY variable and draw its window on that display. The final ampersand backgrounds nohup so you can go on with your day.
user@machine:~$ gnome-mahjongg
Unable to init server: Could not connect: Connection refused
(gnome-mahjongg:2651021): Gtk-WARNING **: 17:29:13.980: cannot open display:
user@machine:~$ pgrep gnome-mahjongg
user@machine:~$ echo $DISPLAY
user@machine:~$ export DISPLAY=:0.0 && nohup gnome-mahjongg &
[1] 2651154
user@machine:~$ nohup: ignoring input and appending output to 'nohup.out'
user@machine:~$ pgrep gnome-mahjongg
2651155Here you see me trying to run gnome-mahjongg on the command line. There’s no $DISPLAY variable, so it fails. pgrep shows there is no mahjongg running.
But, if I export the correct value for $DISPLAY and wrap the game in a nohup runner and send it to the background, gnome-mahjongg starts and is now running on my workstation. I can either kill the process 2651155 here with the usual kill tools (which exits the nohup process running at 2651154), or I can just wait until I get home, unlock my screen, and click the X to close mahjongg after a few rousing games (for testing, of course).
This resolves a fear that I’ve held that I will be out of town and something will happen to make Thunderbird stop running my filters. All it takes is an app crash, an out-of-memory exception, a power outage, the PC rebooting on its own, whatever. Now, as long as X is running, I can send apps to its display. This fear is quelled.
Granted, this doesn’t resolve issues if X is running but I’m not logged in — like if the Gnome Greeter is waiting on me to login. That’s a different issue altogether. Maybe I’ll test that later! But let’s not worry about ourselves too much, eh? Baby steps.