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jlesage / docker-baseimage-gui

A minimal docker baseimage to ease creation of X graphical application containers
MIT License
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Restart xvfb with new DISPLAY_WIDTH and DISPLAY_HEIGHT while container is running #65

Closed m-bers closed 2 years ago

m-bers commented 2 years ago

I am running an image where the output of the CMD is being piped into sed to extract screen width/height values, and store them in DISPLAY_WIDTH and DISPLAY_HEIGHT respectively.

I have KEEP_APP_RUNNING=1 so the container doesn't stop when services are restarted, but when I try to run s6-svc -h /run/s6/services/xvfb/ in an exec session as root it is using the old environment variables loaded from the docker run command. I also tried doing e.g. cat $DISPLAY_WIDTH > /run/s6/container_environment/DISPLAY_WIDTH and it didn't pick that up either.

I know dynamic resize via xrandr isn't working but it'd be great to do a one-time resize via restarting xvfb based on values returned in my entrypoint script. Also, when I try to do this directly from the entrypoint script I get permission denied since s6-svc needs to be run as pid 1. Any way around this other than setting -e USER_ID=0 -e GROUP_ID=0?

Currently the only thing that actually works is mounting my .env file into the container, writing the DISPLAY_WIDTH and DISPLAY_HEIGHT values there and doing a brand new docker run from the directory with the .env file. Needless to say this is not ideal.

jlesage commented 2 years ago

I'm not sure to understand how you would like to change DISPLAY_WIDTH and DISPLAY_HEIGHT while the container is running. Could you provide an example ?

m-bers commented 2 years ago

In this case, I am connecting to a VM console that returns the resolution of the guest in the cli output.

jlesage commented 2 years ago

And how you communicate the resolution to the container once you have it?

m-bers commented 2 years ago

One way could be to use s6-overlay v3 which has support for ordered init scripts that mix longruns and oneshots

I could declare a oneshot service of my app that runs after xvfb first starts (since it needs an X server), filter out the resolution string in the CLI output, then stop xvfb (and my app) and start it again with the new resolution variable.

jlesage commented 2 years ago

Sorry, I'm still not sure to fully understand what you are explaining...

But if I modify /var/run/s6/container_environment/DISPLAY_WIDTH and then run killall Xvfb, the new width is applied.

Could you have an init script that set the environment variable ? Or else define a service that monitors changes in resolution and apply it ?

jlesage commented 2 years ago

Closing this issue. Please re-open if needed.

Note that latest images support remote resizing, meaning that the app is re-sizing according to the browser's window size.