Playing audio in a LXC container

[LouisM]

Hello everybody,
I'm using Proxmox since a year, and I can't figure out what I am missing in my configuration.
I want to play audio files into a unprivileged container.
What I done :

1) Allowing access to the onboard soundcard in the container file :

lxc.cgroup2.devices.allow: c 116:* rwm
lxc.mount.entry: /dev/snd dev/snd none bind,optional,create=dir

After that I can see the card on my LXC container :

total 0
drwxr-xr-x 3 nobody nogroup     300 Dec 17 20:46 .
drwxr-xr-x 7 root   root        500 Dec 17 21:29 ..
drwxr-xr-x 2 nobody nogroup      60 Dec 17 20:46 by-path
crw-rw---- 1 nobody nogroup 116, 11 Dec 17 20:46 controlC0
crw-rw---- 1 nobody nogroup 116,  9 Dec 17 20:46 hwC0D0
crw-rw---- 1 nobody nogroup 116, 10 Dec 17 20:46 hwC0D2
crw-rw---- 1 nobody nogroup 116,  3 Dec 17 20:46 pcmC0D0c
crw-rw---- 1 nobody nogroup 116,  2 Dec 17 21:00 pcmC0D0p
crw-rw---- 1 nobody nogroup 116,  4 Dec 17 20:46 pcmC0D2c
crw-rw---- 1 nobody nogroup 116,  5 Dec 17 20:46 pcmC0D3p
crw-rw---- 1 nobody nogroup 116,  6 Dec 17 20:46 pcmC0D7p
crw-rw---- 1 nobody nogroup 116,  7 Dec 17 20:46 pcmC0D8p
crw-rw---- 1 nobody nogroup 116,  8 Dec 17 20:46 pcmC0D9p
crw-rw---- 1 nobody nogroup 116,  1 Dec 17 20:46 seq
crw-rw---- 1 nobody nogroup 116, 33 Dec 17 20:46 timer

Now I'm stuck.
I understand that I should map UID and GID... But i'm completely lost with it.
Both users are root, so the UID and GID are 0.

Thanks in advance for the help

 

[fschauer]

In unprivileged containers uids and gids in the container are mapped to different ids on the host. If you aim to access files on the host from within a container, the uid or gid of the file in the container needs to be mapped to the same id on the host. A detailed explanation is provided in the wiki: https://pve.proxmox.com/wiki/Unprivileged_LXC_containers

Since PVE 8.1 there is a much simpler way to pass devices through to a container. No need to manually bind mount the device nodes.

pct set <container id> -dev<n> /dev/snd/pcmC0D0c

n is just an arbitrary number from 0 to 255 to identify the device

 

[LouisM]

Thanks a lot for your help!
So it works
My final config file is :

arch: amd64
cores: 1
dev1: /dev/snd/controlC0
dev2: /dev/snd/hwC0D0
dev3: /dev/snd/hwC0D2
dev4: /dev/snd/pcmC0D0c
dev5: /dev/snd/pcmC0D0p
dev6: /dev/snd/pcmC0D2c
dev7: /dev/snd/pcmC0D3p
dev8: /dev/snd/pcmC0D8p
dev9: /dev/snd/pcmC0D9p
dev10: /dev/snd/seq
dev11: /dev/snd/timer
features: nesting=1
hostname: intercom
memory: 512
net0: name=eth0,bridge=vmbr0,firewall=1,hwaddr=BC:24:11:62:08:E8,ip=dhcp,type=veth
onboot: 1
ostype: debian
rootfs: local-lvm:vm-102-disk-0,size=8G
swap: 512
unprivileged: 1

With this configuration, I can't play a sound when another sound is playing on the machine. That's not a problem now but maybe in the future...
Thanks a lot!