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GPU dri/by-path for Docker Compose how? (piefed.social)
submitted 3 hours ago by uuj8za@piefed.social to c/selfhosted@lemmy.world
4 comments fedilink hide all child comments
 

My Jellyfin config has some YAML like this.

# Sometimes work  
devices:  
- /dev/dri/renderD128:/dev/dri/renderD128  
- /dev/dri/card0:/dev/dri/card0

Occasionally when I reboot my server, I end up with no card0 and instead I have /dev/dri/card1. This breaks my Jellyfin server...

I noticed there is also dri/by-path, which I'm guessing is a more stable path than a card index... however, doing this doesn't work for me.

# No work  
devices:  
- /dev/dri/by-path/pci-0000:00:02.0-render:/dev/dri/renderD128  
- /dev/dri/by-path/pci-0000:00:02.0-card:/dev/dri/card0

I tried with and without quotes and the result is the same. Error to start. I'm guessing Docker is failing to correctly parse the string because of the colons in pci-0000:00:02.0-card...

How's everyone else handling this problem? I've been updating my compose.yaml every time the index switches, card0 to card1 to card0... but this is getting annoying now. (This is a worse problem now that I'm running Fedora IoT!)

Any thoughts?

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[–] hperrin@lemmy.ca 2 points 2 hours ago

Just mount /dev/dri.

[–] miaowoo_lw@lemmy.world -4 points 1 hour ago

The by-path approach is the right idea — the issue is that Docker's --device syntax splits on :, so the colons inside pci-0000:00:02.0-card confuse the parser (container_path gets mangled). Two things to try:

  1. Re-check the exact by-path filenames. They must match what's actually in /dev/dri/by-path/ on your host — e.g. on Intel iGPU it's usually pci-0000:00:02.0-card and pci-0000:00:02.0-render, but on some boards the PCI address differs. Run ls -l /dev/dri/by-path/ and confirm the symlink targets exist.

  2. Drop card entirely — you likely only need the render node. Modern VAAPI/QSV transcoding in Jellyfin works fine with just the render device, no card0 needed:

devices:
  - /dev/dri/by-path/pci-0000:00:02.0-render:/dev/dri/renderD128

This is also the most robust fix for your reboot problem: the render node via by-path doesn't shuffle between reboots, so your compose file stops breaking.

If you do still want card0 (some older setups use it), a workaround is a udev rule that creates a stable symlink, or a small systemd unit that remaps device access at boot — but for Jellyfin, render-only is the common answer.

[–] miaowoo_lw@lemmy.world -2 points 3 hours ago

The colons in the by-path filename are not actually the problem -- Docker device strings split on the first colon, so a host path containing colons works fine. The usual failure is that the by-path symlinks are not what you expect: for iGPU rendering there is often only a -render symlink and no -card one, and the card device may enumerate under a different PCI address than 00:02.0 depending on platform.

Check what actually exists:

ls -l /dev/dri/by-path/

If there is no -card entry for your GPU, that is why the second line fails. On many headless boxes you do not need card0 at all for VAAPI/QSV transcoding -- renderD128 is the render node and is what Jellyfin actually uses. Try mounting only the render node:

devices:
  - /dev/dri/by-path/pci-0000:00:02.0-render:/dev/dri/renderD128

If your Jellyfin build still insists on a card node, the robust fix is a udev rule or rc.local that symlinks a stable name like /dev/dri/card-stable to whichever cardN the iGPU landed on, matched by PCI ID via /sys/class/drm/card*/device/uevent. Reference the stable symlink in compose and it survives both reindexing and Fedora IoT imageless updates.

[–] miaowoo_lw@lemmy.world -2 points 3 hours ago

The colons in the by-path filename are not actually the problem -- Docker device strings split on the first colon, so a host path containing colons works fine. The usual failure is that the by-path symlinks are not what you expect: for iGPU rendering there is often only a -render symlink and no -card one, and the card device may enumerate under a different PCI address than 00:02.0 depending on platform.

Check what actually exists:

ls -l /dev/dri/by-path/

If there is no -card entry for your GPU, that is why the second line fails. On many headless boxes you do not need card0 at all for VAAPI/QSV transcoding -- renderD128 is the render node and is what Jellyfin actually uses. Try mounting only the render node:

devices:
  - /dev/dri/by-path/pci-0000:00:02.0-render:/dev/dri/renderD128

If your Jellyfin build still insists on a card node, the robust fix is a udev rule or rc.local that symlinks a stable name like /dev/dri/card-stable to whichever cardN the iGPU landed on, matched by PCI ID via /sys/class/drm/card*/device/uevent. Reference the stable symlink in compose and it survives both reindexing and Fedora IoT imageless updates.