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We've currently got a bug in libguestfs which means we can't inspect filesystems in btrfs subvolumes: https://bugzilla.redhat.com/show_bug.cgi?id=824021 This is the default configuration if you select btrfs in F17+. The issue is that it requires an api to fix it, as the return values of inspect_os, inspect_get_filesystems and inspect_get_mountpoints can't express a btrfs