[Libguestfs] [PATCH FOR DISCUSSION ONLY] Allow setting of user:group for qemu subprocess.

This is an experimental (not working) patch which would allow you to set the user and group of the qemu process, assuming the main program is running as root. The reason for this is to allow access as root to disk images which are located on "root-squashed" NFS volumes. This is a particular concern for virt-v2v. The most immediate problem with the patch (which can be fixed easily) is that the non-root qemu cannot access the appliance: qemu: could not load kernel '/tmp/libguestfsj2CItc/kernel': Permission denied In terms of the bigger picture I'm not convinced that this patch is really going to be useful. Firstly various commands currently try to access the disk image from the main process (notably guestfs_add_drive). Secondly any serious program using libguestfs will want to touch the disk image elsewhere, so the root-squashing problem will have to be tackled there too. It sounds as if for virt-v2v the whole program should just setuid itself to a non-root user as early as possible, rather than pushing this into libguestfs. On the other hand, not running qemu as root even when libguestfs itself is root, is an appealing idea if the permissions issues could be resolved. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into Xen guests. http://et.redhat.com/~rjones/virt-p2v