Investigate guestfstools for mounting as unprivileged user

[maringuu]

For btrfs.img in this repo:

virt-filesystems -a ./fact_extractor/plugins/unpacking/generic_fs/test/data/btrfs.img
guestmount -m /dev/sda -a  ./fact_extractor/plugins/unpacking/generic_fs/test/data/btrfs.img ~/mnt

I haven't looked in depth what filesystems are supported and how it works

[maringuu]

As @jstucke noticed this still needs SYS_ADMIN for finally mounting the filesystem via FUSE.
Apparently this is not needed anymore in Linux 4.18 and can be replaced by mount namespaces. This comment nicely explains how to do this.