[systemd-devel] what does --ephemeral really do on btrfs?

[Johannes Ernst]

If I run systemd-nspawn with —ephemeral, it creates a new temporary btrfs subvolume, the documentation says.

Mine takes an awful long time — blocking IO on the device in the awful long meantime — and I’m puzzled why. Does it perhaps copy (deep? references only?) the entire drive? 

Should I put the original directory on a separate subvolume, or how can I speed this up? If I just copied the image / directory, this might be faster.

Thanks,



Johannes.