[Users] Docker inside an OpenVZ container

[Kir Kolyshkin]

On 03/23/2015 03:12 AM, Benjamin Henrion wrote:
> On Mon, Mar 23, 2015 at 10:55 AM, Narcis Garcia <informatica at actiu.net> wrote:
>> As I read from Ubuntu/Debian package (version 0.9.1):
>>
>> Docker complements kernel namespacing with a high-level API which
>> operates at the process level. It runs unix processes with strong
>> guarantees of isolation and repeatability across servers.
>>
>> Docker is a great building block for automating distributed systems:
>> large-scale web deployments, database clusters, continuous deployment
>> systems, private PaaS, service-oriented architectures, etc.
>>
>> This package contains the daemon and client. *Using docker.io on
>> non-amd64 hosts is not supported at this time*. Please be careful when
>> using it on anything besides amd64.
>>
>> Also, note that *kernel version 3.8 or above is required* for proper
>> operation of the daemon process, and that any lower versions may have
>> subtle and/or glaring issues.
> Redhat backported a lot of LXC features to 2.6.32, so that's one of
> the reasons you can run docker/lxc on top of the openvz kernel.

In addition to that, we did a significant amount of kernel work
to allow running Docker inside our containers.

In general, OpenVZ kernel version (which is 2.6.32) has very little
to do with vanilla 2.6.32, so this number doesn't really mean anything
except that Red Hat kernel team branched their kernel off this
version when they started working on RHEL6.

Currently this is 2.6.32 plus tons of patches from Red Hat plus
a pretty big patchset from OpenVZ. In particular, we make sure all the
recent distros work inside containers, so sometimes we have to backport
some new syscall or other feature from recent kernels.

 From time to time I see people saying OpenVZ kernel is very old and
obsoleted. It happens because the judge by the label, and the label starts
with 2.6.32. Indeed, 2.6.32 is a very old kernel, but as I explained above
our kernel has very little to do with 2.6.32.