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Tips / Solutions for settings up OpenVPN on Debian 9 within Proxmox / LCX containers

by robert on September 21, 2017

When I tried to migrate my OpenVPN setup to a container on my new Proxmox server I run into multiple problems, where searching through the Internet provided solutions that did not work or were out of date. So I thought I put everything one needs to setup OpenVPN on Debian 9 within a Proxmox / LXC container together in one blog post.

Getting a TUN device into the unprivileged container

As you really should run container in unprivileged mode the typical solutions with adding/allowing

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

won’t work. And running a container in privileged mode is a bad bad idea, but gladly there is a native LXC solution.

Stop the container with

pct stop <containerid>

Add following line to /etc/pve/lxc/<containerid>.conf

lxc.mount.entry = /dev/net/tun dev/net/tun none bind,create=file

start the container with

pct start <containerid>

OpenVPN will now be able to create a tun device. Just do a test run with

openvpn --config /etc/openvpn/blabla.conf

Add OpenVPN config files to the “autostart”

You need to put the OpenVPN files into /etc/openvpn/ with the extension .conf. And if you add a new file you need to run

systemctl daemon-reload

before doing a service openvpn restart.

Changes in existing config files don’t need the systemd reload.

Getting systemd to start openvpn within a unprivileged container

So OpenVPN works now manually but not with the “init” script. You see following error message in the log file
daemon() failed or unsupported: Resource temporarily unavailable (errno=11)

To solve this edit

/lib/systemd/system/[email protected]

and but a # in front of

LimitNPROC=10

now reload systemd with

systemctl daemon-reload

and it should work.

Hope that info/tips helped you to solve the problems faster than I did. If you know some other tips / solutions for running OpenVPN in a Debian 9 container withing LXC / Proxmox write a comment! Thx!