This can be used to mount an OCI+squashfs image. If you are host root, then squashfs will be mounted by the kernel. If you are container root but not host root, then squashfuse will be used.

Example:

atomfs mount containers/oci:minbase:latest mnt
atomfs umount mnt

Longer example:

$ lxc-usernsexec -s
$ atomfs mount zothub:busybox-squashfs dest
$ ls dest
bin  dev  etc  home  lib  lib64  root  tmp  usr  var
$ atomfs umount dest
$ mkdir upper
$ atomfs mount --upper=./upper zothub:busybox-squashfs dest
$ ls dest
bin  dev  etc  home  lib  lib64  root  tmp  usr  var
$ touch dest/ab
$ atomfs umount dest
$ ls upper/
ab

We create $mountpoint/meta and pass that to stacker/atomfs as the Metadatapath. We do the readonly stacker/atomfs molecule mount onto $metadir/ro. Then if a readonly mount is requested $metadir/ro is bind mounted onto $metadir. Otherwise, we create $metadir/work and $metadir/upper, and use these to do a rw overlay mount of $metadir/ro onto $mountpoint.

Note that if you simply call umount on the mountpoint, then you will be left with all the individual squashfs mounts under dest/mounts/*/.

Note that you do need to be root in your namespace in order to do the final bind or overlay mount. (We could get around this by using fuse-overlay, but creating a namespace seems overall tidy).