diff, overlay, and space reuse

[ultranity]

Currently enroot seems to be inflating the sqsh image every time when it's created if they are under different name, which means the space usages will grow as the instance num since we are duplicating the content file system everytime.

I have found some relavant overlayfs mount code in

enroot/src/runtime.sh

Line 158 in 1cebc0c

fuse-overlayfs -f -o "lowerdir=${rootfs}/lower,upperdir=${rootfs}/upper,workdir=${rootfs}/work" "${rootfs}" &

, but when I'm using the $ENROOT_RUNTIME_PATH only consists of some empty folder and all file changes inside the container happens in $ENROOT_DATA_PATH. I'm not sure if there are some missing configs that caused this situation?

furthermore, is it possible to implement something like volume overlay so we can share the root filesystem and track changes like docker diff?