Due to built-in security of LXC, trying to setup a tunnel interface inside a container is by blocked by default.
ERROR: Cannot open TUN/TAP dev /dev/net/tun
To allow this for a specific container in Proxmox, we need to make a few tweaks to allow this interface to work in a specific container (we don’t want to allow all containers to be able to setup a tunnel – hackers can hide their tracks using it).
How to do this:
ADD these lines to /etc/pve/lxc/<container-id>.conf
lxc.cgroup.devices.allow = c 10:200 rwm
lxc.hook.autodev = sh -c "modprobe tun; cd ${LXC_ROOTFS_MOUNT}/dev; mkdir net; mknod net/tun c 10 200; chmod 0666 net/tun"
