OpenVPN (server) in Linux containers

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Revision as of 09:50, 29 December 2016 by Graysky (talk | contribs) (Host setup: list)
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This article describes how to setup a Linux Container to run OpenVPN in server mode for secure/private internet use. Doing so offers a distinct advantage over using full-blown virtualization like VirtualBox or QEMU in that the resource overhead is minimal by comparison and able to run on low powered devices.

Host setup

  1. The host OS needs a bridge ethernet setup to allow the container to run. Refer to Linux_Containers#Host_network_configuration for this.
  2. One needs to enable packet forwarding. Refer to Internet_sharing#Enable_packet_forwarding for this.
  3. Although not strictly required, a firewall is highly recommended.

Container setup

Basic setup and understanding of Linux Containers is required. This article assumes that readers have a base LXC setup and operational. New comers to these are directed to the aforementioned article.

LXC config

The container's config should be modified to include several key sections in order run OpenVPN.

For the example, the lxc is named "playtime" and a full config is shown:

/var/lib/lxc/playtime/config
# Template used to create this container: /usr/share/lxc/templates/lxc-archlinux
# Parameters passed to the template:
# For additional config options, please look at lxc.container.conf(5)

lxc.rootfs = /var/lib/lxc/playtime/rootfs
lxc.utsname = playtime
lxc.arch = x86_64
lxc.include = /usr/share/lxc/config/archlinux.common.conf

## network
lxc.network.type = veth
lxc.network.link = br0
lxc.network.flags = up
lxc.network.name = eth0

## systemd within the lxc
lxc.autodev = 1
lxc.hook.autodev = /var/lib/lxc/playtime/autodev
lxc.pts = 1024
lxc.kmsg = 0

## mounts
lxc.mount.entry = /var/cache/pacman/pkg var/cache/pacman/pkg none bind 0 0

## for openvpn
lxc.cgroup.devices.allow = c 10:200 rwm
Note: This example requires the use of the autodev hook which calls the corresponding /var/lib/lxc/playtime/autodev script which users need to create and make executable. For the sake of completeness, this script is provided below. Refer to Linux Containers for additional discussion if needed.
/var/lib/lxc/playtime/autodev
#!/bin/bash
cd ${LXC_ROOTFS_MOUNT}/dev
mkdir net
mknod net/tun c 10 200
chmod 0666 net/tun

Needed packages within the container

In addition to the base system, openvpn is required and available from the official repositories. A properly configured firewall to run within the container is highly recommended. This guide uses ufw which is very easy to configure, but other examples can certainly be used.

Package setup

OpenVPN

Refer to the OpenVPN article to properly setup the home server. Verify openvpn functionality within the container; start openvpn via openvpn@myprofile.service and once satisfied enable it to run at boot.

ufw

Refer to OpenVPN#Firewall configuration to setup the routes and firewall within the container. Failure to do so or to implement with an alternative will prevent openvpn from functioning properly in the container.

Start ufw and enable ufw.service to start at boot.

# ufw enable