[Libguestfs] [PATCH] Add virtio-scsi support to febootstrap.

[Richard W.M. Jones]

This patch is the minimum possible to add virtio-scsi support to
febootstrap.

Problem: SCSI devices are detected asynchronously after the Linux
kernel module is loaded.

The usual solutions to this involve scsi_wait_scan (deprecated
apparently) or udev.  However febootstrap doesn't use udev, and adding
it is a ton of work with a very uncertain outcome.

So the minimum possible change is to have libguestfs pass in the
appliance device on the Linux command line (eg. root=/dev/sdb) and
then busy-wait until it becomes available in the initramfs.

Rich.