[lxc-devel] Overlayfs multiple lower layers support in LXC

[Tobby Banerjee]

Hi All,

Overlayfs was merged 3.18 and overlayfs in 4.0.4 adds support for multiple
lower layers.

Current LXC snapshot can so single layers, is there any plan to support
mulitple lower layers?

The main advantage I see is you can do snapshot of base OS and then add an
app and snapshot that, and these 2 can be your seed container. You then
mount the rootfs of base OS and delta0 of snapshot1 with 2 overlays lower
layers as the rootfs of your deploy container.

I have put together a small script that does exactly that including a
pre-mount hook for the 2 lower overlayfs layers and it seems to work well
enough.

The limitation of one lower layer is if you want to deploy 5 apps across
lets say 50 containers,  then having a single level snapshot will force you
to have 5 base level OS containers for each of the apps. With 2 lower
layers you can have a single base OS container and 5 overlay snapshots for
each of the apps.

Thanks

Tobby
www.flockport.com
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