Mounting overlay filesystems with libguestfs

libguestfs is a set of tools for accessing and modifying virtual machine (VM) disk images. It can typically inject files in VM images, create or modify partitions, set partition labels and even expose the VM image content on a host mountpoint all this without root access.

Under the hood, libguestfs spawns a Qemu/KVM virtual machine with all needed tools and relies on Fuse to expose the filesystem to a non privileged user mountpoint.