Proxmox-passing-device-in-LXC.md

Proxmox: Passing Host Devices into LXC Containers

This document explains common ways to pass host devices into Proxmox LXC containers. Examples use /dev/net/tun.

Applies to: Proxmox VE with LXC (cgroup v2)

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Option 1: Bind-mount a Device (Classic / Manual Way)

This method is useful for advanced or legacy setups. For most cases, Option 2 is recommended.

1. Check device information on the host

ls -lah /dev/net

Example output:

total 0
drwxr-xr-x  2 root root      60 Jan 11 08:37 .
drwxr-xr-x 22 root root    4.9K Jan 11 08:37 ..
crw-rw-rw-  1 root root 10, 200 Jan 11 09:37 tun

• Major number: 10
• Minor number: 200
• Type: c (character device)

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2. Modify the LXC config

Edit /etc/pve/lxc/<lxc-id>.conf, add:

lxc.cgroup2.devices.allow: c 10:200 rwm

lxc.mount.entry: /dev/net dev/net none bind,optional,create=dir
# or
lxc.mount.entry: /dev/net/tun /dev/net/tun none bind,optional,create=file

Explanation

lxc.cgroup2.devices.allow

• Allows the container to access a specific device.
• c → character device
• 10:200 → major:minor number
• rwm permissions:
  • r = read
  • w = write
  • m = mmap (required by many drivers)

lxc.mount.entry

• Bind-mounts the host’s /dev/net directory into the container at /dev/net (or /dev/net/tun file).
• optional: Do not fail container startup if the source path is missing. (useful for hot-plug or non-critical devices).

3. Restart the container

pct restart <lxc-id>

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Option 2: Proxmox Device Passthrough (Recommended / New Way)

Proxmox provides a simpler syntax that automatically handles:

• cgroup permissions
• bind mounts
• ownership inside the container

Edit /etc/pve/lxc/<lxc-id>.conf, add:

dev0: /dev/net/tun,gid=0,uid=0

Explanation

• dev0
  • Arbitrary index (dev0, dev1, …)
• /dev/net/tun
  • Device path on the host
• uid (optional)
  • User ID owning the device inside the container
• gid (optional)
  • Group ID owning the device inside the container

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References

• Proxmox GPU sharing with multiple LXCs
• Debian LXC bind mounts