Installing grub on root.img require some space before the filesystem.
Create it by adding partition table to root.img. This commit take care
of assembling dmroot device when such partition table is present, while
preserving compatibility with partition-less images.
QubesOS/qubes-issues#2577
This hook require new device nodes to appear in /dev. If devtmpfs is
used, it's not a problem ("simple" initramfs case), but otherwise udevd
is needed - and it isn't running in pre-udev hook yet.
QubesOS/qubes-issues#2577
New version of sfdisk have different syntax for other units (suffixes
beside the numbers, instead of global --unit). The only common unit is
sector, so use that.
FixesQubesOS/qubes-issues#1427
This makes is possible to modify /lib/modules content - especially
install other kernel packages, without unmounting the whole
/lib/modules. Since dom0-provided modules will no longer conflict with
VM kernel packages (assuming kernel versions are different), there is no
need for qubes-kernel-vm-placeholder anymore.
Having only one subdirectory of /lib/modules mounted is somehow tricky,
because:
1. Directory name isn't always the same - it depends on kernel version.
This means that mountpoint must be created dynamically (so $NEWROOT must
be mounted in R/W for a moment).
2. There is one-command way to mount only a subdirectory of some
filesystem. So use a trick: mount it in some temporary directory, get
interesting subdir with `mount --bind`, then unmount temporary
directory.
QubesOS/qubes-issues#1354
