[SOLVED] OpenVPN Tun\Tap device - Cannot open TUN/TAP dev /dev/net/tun: No such file or directory (errno=2)

[is-max]

Hi,

We use LXC (and had used OpenVZ) mainly for openvpn, I got a problem wich a lot of people are encontering with LXC, the error message:
Cannot open TUN/TAP dev /dev/net/tun: No such file or directory (errno=2)

Today I had and hard day, with the Ubuntu 12.04 and debian 8 template for LXC,
because OpenVPN refuses to start during the boot, despite the device was there, when you log-in.

After an entire day, I found the problem and a solution.

The problem:
OpenVPN SysV Startup script is called before the Upstart /etc/init/mounted-dev.conf .

The solution I had to use was to write a configuration file in:

File: /usr/share/lxc/config/common.conf.d/02-openvpn-auto-tun.conf

lxc.hook.autodev = /usr/share/lxc/hooks/openvpn-auto-tun

Then copy the script I've found on Archlinux website in:

File: /usr/share/lxc/hooks/openvpn-auto-tun

#!/bin/bash
cd ${LXC_ROOTFS_MOUNT}/dev
mkdir net
mknod net/tun c 10 200
chmod 0666 net/tun

Set the right permission to the script file:

chmod 755 /usr/share/lxc/hooks/openvpn-auto-tun

Then, stop\shutdown (don't reboot) and start again the LXC Container, and it will magically work.

I hope, that it will be usefull for someone else, who will arrive here for the same problem.

Regards

-- For future reference the used version of ProxMox is 4.1-1/2f9650d4 --

 

[eth]

Warning!!! Do not use this solution - it will cause your proxmox to break - you will loose SSH access to your system.
For some reason using autodev causes a bug to appear: https://forum.proxmox.com/threads/pct-start-killed-my-whole-proxmox-server-again.26468/

 

[fabian]

That probably interferes with our own autodev hook. The workaround posted by eth in https://forum.proxmox.com/threads/tun-devices-in-ve-4-lxc.23473/#post-132952 seems to work, but be careful what device nodes you allow your container to create and use, because you might create security risks there.