Containerized LibreElec

LibreElec provides a great Kodi build for select hardware architectures. It also provides 'Just enough OS for KODI'.

Raspberry Pi 4 with 8GB memory is a very capable machine, having it running only Kodi feels like a waste of resources. I also prefer 'Just enough OS for me', default/linux/arm64/23.0/musl with FEATURES="distcc noman noinfo nodoc" produces a relatively compact build.

Preparing the environment

Podman provides an easier way to run rootless containers, running Kodi as root isn't a good idea.

1. set up a new user to run Podman/Kodi, adding this user to sudoers wouldn't be a good practice
2. add the user to video, render, input, audio and possibly pipewire groups
3. follow the https://github.com/containers/podman/blob/main/docs/tutorials/rootless_tutorial.md to configure /etc/subuid and /etc/subgid
4. make sure the user is allowed to map required groups

$ cat /etc/subgid
<kodi-user>:<'video' gid>:1
<kodi-user>:<'render' gid>:1
<kodi-user>:<'input' gid>:1
...

Example:

$ cat /etc/subgid
kodi-user:666:1
kodi-user:69:1
kodi-user:420:1
kodi-user:165536:65536
...

5. set up Pipewire-pulse/PulseAudio for the user
6. you might also need to make sure udev sets correct permissions on these devices:

$ cat /etc/udev/rules.d/01-video.rules
KERNEL=="vcsm-cma", GROUP="video", MODE="0660"
SUBSYSTEM=="dma_heap", GROUP="video", MODE="0660"

Building the image

First stage of the multi-stage build uses latest Ubuntu image to download LibreElec disk image and extract root filesystem content using Fatcat (please don't fat shame cats 😽) and squashfs-tools. Second stage creates root fs from the extracted files, removes a few obviously redundant files and disables/removes LibreElec settings Kodi addon.

podman build -t localhost/libreelec:rpi4-12.0.0 --build-arg=dl_url=https://releases.libreelec.tv/LibreELEC-RPi4.aarch64-12.0.0.img.gz .

Running container

1. find out video, render and input image gids

$ podman run -t --rm --entrypoint=/bin/ash localhost/libreelec:rpi4-12.0.0 -c "egrep '(video|render|input)' /etc/group"
video:x:39:pipewire
input:x:104:
render:x:105:

2. start Kodi:

podman run --rm --replace --init --privileged \ #as privileged as the user running podman
  --name kodi \ #keep it obvious
  --hostname kodi \
  --group-add keep-groups \ #keep the groups host user is in
  --gidmap="+g39:@666:1" \ #but also map this container gid to that host gid
  --gidmap="+g105:@69:1" \
  --gidmap="+g104:@420:1" \
  -v /dev/input:/dev/input:ro \ #r/o mount /dev/input
  -v /run/udev:/run/udev:ro \ #r/o mount /run/udev
  -v <path-to-kodi-storage-dir>:/storage \ #mount LibreElec /storage on a local dir
  -v $XDG_RUNTIME_DIR/pulse/native:/tmp/pulse-socket \ #mount host PulseAudio socket
  -e KODI_HOME=/usr/share/kodi \ #Kodi setup
  -e KODI_TEMP=/storage/.kodi/temp \
  -e HOME=/storage \
  -e PULSE_SERVER=unix:/tmp/pulse-socket \
  -p 8080:8080 \ #Kodi web UI ports
  -p 9090:9090 \
  libreelec:rpi4-12.0.0

Tradeoff

You get the same great LibreElec Kodi build only with enhanced security and usability, running on the GNU/Linux flavour of your choice. However, LibreElec settings addon is useless in this case. Meaning all hardware configuration is done on the underlying OS level. Kodi 'power' button does nothing, Kodi built-in services can be forwarded but setting up e.g samba and shairport on host (or in other containers) would be a better option.