Docker inside CT vz7

Since Virtuozzo 7 kernel vzkernel-3.10.0-327.18.2.vz7.14.7 it is possible to run Docker inside containers. This article describes how.
This page is applicable for Virtuozzo 7 (for OpenVZ 6 see here).

Prerequisites

• Kernel 3.10.0-327.18.2.vz7.14.7 or later version
• Kernel modules veth and overlay loaded on host

Note: if you use kernel >= 3.10.0-327.18.2.vz7.14.25, you need to allow using "overlayfs" inside a Virtuozzo Container:

echo 1 > /proc/sys/fs/experimental_fs_enable

Container tuning

• Turn on bridge feature to allow docker creating bridged network:

vzctl set $veid --features bridge:on --save

• Setup Container veth-based network (Container must be veth-based, not venet-based):

vzctl set $veid --netif_add eth0 --save

• Allow all iptables modules to be used in containers:

vzctl set $veid --netfilter full --save

Limitations

• Only overlay and vfs Docker graph drivers are currently supported
• Checkpointing and live migration of a container with Docker containers inside is not supported yet (to be done)