LXD container ALSA audio support

LXD
1

host: Ubuntu 18.04 LXD/LXC 3.0.3

I am trying to use ALSA in my ubuntu 18.04 container. ALSA on host works. I have seen this post but it doesn’t work for me.

My configuration:

lxc config set mycontainer raw.lxc "lxc.cgroup.devices.allow = c 116:* rwm"
lxc config set mycontainer raw.lxc "lxc.mount.entry = /dev/snd dev/snd none bind,optional,create=dir 0 0"

aplay: aplay -l aplay: device_list:270: no soundcards found…

ALSA on the host works perfectly well.

I need it for a home automation text-to-speech functionality.

What else do I need to do to get it working?

Thank you in advance.

2

Hi!
Does your host have Pulseaudio?

If the software can use Pulseaudio instead, then you can share the Pulseaudio’s Unix socket. It’s a single thing to do. See more on this at https://blog.simos.info/how-to-easily-run-graphics-accelerated-gui-apps-in-lxd-containers-on-your-ubuntu-desktop/

3

@simos,

Thank you for this info. I would prefer not to install pulseaudio on my host/server, it would be much simpler to use ALSA if it is possible of course.

4

I guess, I have managed to get it working.
Found this post

lxc config device add <container> pcmC0D2c unix-char path=/dev/snd/pcmC0D2c
I have added all devices listed in /dev/snd:

controlC0 hwC0D0 hwC0D2 pcmC0D0c pcmC0D0p pcmC0D10p pcmC0D1p pcmC0D2c pcmC0D3p pcmC0D7p pcmC0D8p pcmC0D9p seq timer

It is important to add seq and timer, as well.

2 Likes
5

It seems that /dev/snd/pcmXXXX are random. When reboot the host, all /dev/snd/pcmXXXX changes. So I think mount /run/user/<uid>/pulse/native to container is easier.

6

Have you managed to find “permanent” flexible solution for it, if pcmXXX are indeed random as mentioned by @abcfy2?

7

I do not think that they are random. Check this article. I have restarted my server numerous times and those pcm’s have never been changed.

1 Like
8

@lk7777, have you had to manualy change group for container’s /dev/snd/* devices? Mine were owned by root and not audio so I couldn’t get aplay to work till I reworked my audio profile to include gid.
Also, it appeared that lxc config set mycontainer raw.lxc is not required, at lest speaker-test works without it.

So for anyone interested (I’m using RaspberryPi 4, so it probably should work for others)

config:
  user.user-data: |
    #cloud-config
    packages:
      - alsa-utils
description: ALSA LXD profile
devices:
  controlC0:
	gid: "29"
    path: /dev/snd/controlC0
    type: unix-char
  controlC1:
	gid: "29"
    path: /dev/snd/controlC1
    type: unix-char
  pcmC0D0p:
	gid: "29"
    path: /dev/snd/pcmC0D0p
    type: unix-char
  pcmC1D0p:
    gid: "29"
    path: /dev/snd/pcmC1D0p
    type: unix-char
  seq:
	gid: "29"
    path: /dev/snd/seq
    type: unix-char
  timer:
	gid: "29"
    path: /dev/snd/timer
    type: unix-char
name: audio-alsa
used_by:
9

On my host /dev/snd root:audio and I do use mounting:
lxc config set mycontainer raw.lxc "lxc.mount.entry =

One thing that I added to the configuration is mode: "0666"

So it looks like this:

  seq:
    mode: "0666"
    path: /dev/snd/seq
    type: unix-char
10

:slight_smile: "mode: “0666” - that explains.
It works, but, probably, not inline with recommendations, as host’s policy is “0660” for those. Ok, tnx!

11

I know it is dirty but I trust my container, there is nothing to worry about, it is just a /snd :wink:

12

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