GUI works over headless ssh, does not work locally

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GUI works over headless ssh, does not work locally

Postby fionnbharr » Fri Jan 14, 2022 3:28 pm

I've been running a RPi-3B as a remote/headless box for a while; all setup after the initial install was done over ssh. Xorg and LXDE were installed remotely, and everything's been working fine: ssh -X allows me to start whatever application I need, and the remote interface, while occasionally laggy, works just fine.

I happened to hook up a monitor and keyboard for the first time since the initial install, and startx displays a black/blank screen. I think that means X is actually working. But there's no mouse cursor, an unresponsive keyboard, no alternate TTY's. Even 'exec twm' in .xinitrc isn't helping things.

Suggestions towards getting a local graphical interface up and running are appreciated.
fionnbharr
 
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Re: GUI works over headless ssh, does not work locally

Postby fionnbharr » Sat Jan 15, 2022 6:03 pm

The contents of ~/.xinitrc are being executed:

Code: Select all
$ ps aux | grep xterm
fionn      473  0.0  0.8  17004  7668 tty1     S    17:50   0:00 xterm -geometry 80x66+0+0 -name login
fionn      479  0.0  0.8  17020  7692 tty1     S    17:50   0:00 xterm -geometry 80x50+494+51
fionn      480  0.0  0.7  17080  7500 tty1     S    17:50   0:00 xterm -geometry 80x20+494-0
fionn      530  0.0  0.1   2728  1452 pts/3    S+   17:58   0:00 grep xterm


And twm is also shows up as running.

So this means that xorg is working, but it's not able to display any of the specified/running xterms. The only error showing up in Xorg.0.log:
Code: Select all
[    90.542] (EE) open /dev/fb0: Permission denied


And, again, calling any graphical application (such as xterm) from an X-enabled ssh session shows up with no problem on the remote box; this is only a problem on the local box.

Still looking for suggestions.
fionnbharr
 
Posts: 19
Joined: Mon Apr 20, 2015 12:48 am

Re: GUI works over headless ssh, does not work locally

Postby Mettacrawler » Tue Jan 18, 2022 3:18 pm

Stack exchange "startx cannot open /dev/fb0: Permission denied"
https://unix.stackexchange.com/question ... ion-denied

Arch wiki "Rootless Xorg"
https://wiki.archlinux.org/title/xorg#Rootless_Xorg

To configure rootless Xorg using xinitrc:

    Run startx as a subprocess of the login shell; run startx directly and do not use exec startx.
    Ensure that Xorg uses virtual terminal for which permissions were set, i.e. passed by logind in $XDG_VTNR via .xserverrc.
    If using certain proprietary display drivers, kernel mode setting auto-detection will fail. In such cases, you must set needs_root_rights = no in /etc/X11/Xwrapper.config.

For the $XDG_VTNR part this is an example:

Code: Select all
$ cat .xserverrc
#! /bin/bash

exec /usr/bin/Xorg -nolisten tcp "$@" vt"$XDG_VTNR"
Mettacrawler
 
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Re: GUI works over headless ssh, does not work locally

Postby fionnbharr » Thu Jan 20, 2022 3:13 pm

Stack exchange "startx cannot open /dev/fb0: Permission denied"
https://unix.stackexchange.com/question ... ion-denied

Arch wiki "Rootless Xorg"
https://wiki.archlinux.org/title/xorg#Rootless_Xorg


I've seen both of these; It's my understanding that the permission issues were fixed years ago (the first link is over seven years old); I've never had to adjust permissions before with Arch on any of my other RPi's. I've got two other Arch RPi's with working X locally -- I'm wondering what's different about this one.

For troubleshooting & grins, I swapped out the microSD card, and installed Manjaro on the new card -- because Manjaro is basically "pre-installed Arch+DE"; the symptoms are the same: X loads, but with a blank screen, and all applications can be accessed remotely using 'ssh -X'. I swapped out the microSD card again, this time using RaspbianOS -- and it works as expected with local graphics. A third swap with a brand-new Arch install has the same problem; no locally useable X, and since the permission issues have been fixed in recent releases, I don't believe that's the issue.

This suggests the issue is specific to Arch-based installs, what with the similar symptom using Manjaro, but not with others.

Did I miss something basic in the install process? I followed the instructions on Archlinuxarm.org, and then followed the General Recommendations in the Arch Wiki. Again, X runs, but there's none of the requested applications displayed.
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Joined: Mon Apr 20, 2015 12:48 am


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