[Lxc-users] lxc containers as backup 'replicas'

[Fajar A. Nugraha]

On Wed, Jun 5, 2013 at 6:50 PM, Rory Campbell-Lange
<rory at campbell-lange.net> wrote:
> There are 4 parts to a running machine that I will need to replicate to
> a lxc container, which I intend to do nightly. These are:
>
>     1. etc configuration (we back config files up through etckeeper)
>     2. binaries (we're happy with a dpkg -l listings here)
>     3. run-time config for web apps (we back up through a file backup)
>     4. database backup (backed up via log shipping)
>
> I'd be grateful to know if it is possible to sync 1. and 3. into the
> container when it is not running. In other words, to simply update the
> config files in /var/lib/lxc/<container>/rootfs/etc, for example?

Should be possible.

However, personally I'd just forget for a moment that the backup will be
run on lxc and do the same things I'd do on a normal machine.

In my case, I'd use zfs snapshot and send|receive (yes, you can use zfs
for root). In your case it'd probably be rsync or whatever you're happy with.

>
> On another point I'd also like to know of the recommended way of using
> another mount point for lxc containers and the dpkg cache. For example,
> I wish to hold my containers in /dev/sdb/ mounted on /containers. Should
> I symlink /var/lib/lxc/ to this mount point?

I'm pretty sure there were problems wiith that on some versions on lxc
(can't remember the exact details, sorry). A bind mount would probably
be safer.

>
> Finally I'd be grateful to learn of people's experiences with btrfs for
> snapshotting and managing containers. I personally use it for my laptop
> backups, but my host server is on a 3.2.0-4-amd64 kernel which is pretty
> old by btrfs standards.

Is there a particular requirement for that version of kernel? In
RHEL/Centos/Ubuntu you can often use prebuilt latest vanilla kernel
with only minimum change required (although the distro won't offically
support it, obviously).

If you're stuck with kernel 3.2 then I'd say use zfs. The devs take extra
care to make sure it works well on RHEL6 (with its ancient 2.6.32 kernel),
and should work on all kernel from that version up to 3.9.

-- 
Fajar