I'm on stable libguestfs-1.44.1 virt-filesystems (and probably other tools) are now busted. This is the first time I've tried it since upgrading to qemu-6.1.0 $ virt-filesystems -a /mnt/ssd1/VMs/win11.qcow2 libguestfs: trace: set_verbose true libguestfs: trace: set_verbose = 0 libguestfs: create: flags = 0, handle = 0x56112a90d9e0, program = virt-filesystems libguestfs: trace: add_drive "/mnt/ssd1/VMs/win11.qcow2" "readonly:true" libguestfs: creating COW overlay to protect original drive content libguestfs: trace: get_tmpdir libguestfs: trace: get_tmpdir = "/tmp" libguestfs: trace: disk_create "/tmp/libguestfsLWJ0gj/overlay1.qcow2" "qcow2" -1 "backingfile:/mnt/ssd1/VMs/win11.qcow2" libguestfs: command: run: qemu-img libguestfs: command: run: \ create libguestfs: command: run: \ -f qcow2 libguestfs: command: run: \ -o backing_file=/mnt/ssd1/VMs/win11.qcow2 libguestfs: command: run: \ /tmp/libguestfsLWJ0gj/overlay1.qcow2 qemu-img: /tmp/libguestfsLWJ0gj/overlay1.qcow2: Backing file specified without backing format Detected format of qcow2.libguestfs: error: qemu-img: /tmp/libguestfsLWJ0gj/overlay1.qcow2: qemu-img exited with error status 1, see debug messages above It appears qemu-img now errors out instead of giving a warning for this condition: https://gitlab.com/qemu-project/qemu/-/commit/497a30dbb065937d67f6c43af6dd78492e1d6f6d Thanks
Yeah that's unfortunate. It requires modification of libguestfs and virt-v2v in a few places to cope.
In the meantime you can work around the problem by using the --format parameter (eg. virt-filesystems --format=raw -a ...). But you shouldn't need to do that so we'll need to have libguestfs do the autodetection.
Upstream fix is: https://github.com/libguestfs/libguestfs/commit/45de287447bb18d59749fbfc1ec5072413090109 I'll push this for Fedora 34 and Rawhide later today since those are the only versions of Fedora with this qemu.
I mean Fedora 35 and Rawhide.
Closing since this bug is fixed upstream.