Creating container from rootfs tgz

RobMar · September 28, 2021, 11:42am

What’s the best way to create an lxd container from an arbitrary rootfs tgz file?

My colleagues are working with Yocto Linux and generating root filesystems in tgz format. I’ve been able to import these files directly into Docker and WSL. But I still haven’t worked out how to do the equivalent in LXD.

I suspect the best way today is to use distrobuilder --pack-lxd, but I haven’t been able to find any usage examples. Do I need to create the .yaml file? Can someone provide a real example?

Dnegreira · September 28, 2021, 2:18pm

Hi,

When using distrobuilder to build custom images I usually borrow the .yaml from the LXD CI repository.
An example for Ubuntu: https://github.com/lxc/lxc-ci/blob/master/images/ubuntu.yaml but you have a couple others in there as well.

RobMar · September 28, 2021, 3:49pm

Thanks. It seems that using distrobuilder would be more complicated than I had hoped: there’s lots to understand in the yaml files. But I stumbled on this alternative approach:

Create an empty container using the REST API (LXD: How to create an empty container (rootfs empty) - #3 by stgraber)
Mount the storage (e.g. sudo zfs mount poolname/containername)
Untar into the rootfs folder
Fix the permissions: chgrp -R 100000:100000 rootfs
Unmount the storage
Start the container

This works for me (so far!)

tomp · September 28, 2021, 4:30pm

You can also then export that as an image using lxc publish.