Re: [libvirt] [Qemu-devel] [PATCH v2] Add support for fd: protocol

> Incremental support is fine by me, but we'll need it sooner or later. Qemu currently opens the specified copy-on-write file, finds a backing file name in the opened file's header, opens that backing file, and repeats. So it seems that either a backingN= would be needed or a way to map a file descriptor to the file name in the header. I think the latter is along the lines of what was discussed here with -blockdev: http://lists.gnu.org/archive/html/qemu-devel/2011-05/msg02417.html Repeating the syntax specified in that thread, you'd have: -blockdev id=foo-base,path=fd:4,format=raw -blockdev id=foo,path=fd:3,format=qcow2,backing_file=foo-base where id is the file name. This chains the backing files on the command line.