The only ftypes supported by Incus are:
incus.tar.xz
(metadata tarball)squashfs
(preferred for container images)squashfs.vcdiff
(used for delta images)root.tar.xz
(fallback for container images)incus_combined.tar.gz
(very rarely used, allows for a single file per image)disk-kvm.img
(preferred for VM images)disk1.img
(fallback for VM images)uef1.img
(fallback for VM images)
So in most cases, a valid container image should have an incus.tar.xz
ftype and either squashfs
or root.tar.xz
. A valid VM image should have an incus.tar.xz
ftype and a disk-kvm.img
.