dracut-ntfsloop: Mount image on NTFS partition

This dracut module allows you to use a root system located inside a disk image on a NTFS partition, similar to how Wubi worked.

Requirements

• dracut (tested with Fedora 23)
• fuse, ntfs-3g, kpartx, losetup
• fuse and loop kernel modules available

The disk image should contain a full partition table. You'll usually create this by installing your linux distro of choice in qemu.

Installation

• copy the 90ntfsloop directory to /usr/lib/dracut/modules.d
• regenerate your initrd using dracut --force
• add to your kernel command line: rd.ntfsloop=/PATH/TO/DEVICE:PATH/TO/IMAGE/IN/PARTITION where /PATH/TO/DEVICE can be like /dev/sda1 but also UUID=....

You'll want to do this while your system is still running inside qemu.

Booting

To boot the final system, your /boot partition will need to be accessible by your boot loader of choice. You can use grub2's ntfs support combined with its ability to access partitions on a loopback image to make this a breeze.

I installed grub2 onto a flash drive ( grub2-install --no-floppy /dev/sdX --boot-directory=/mount/point/of/sdX) and set up a config file (grub2/grub.cfg) similar to this:

loopback l (hd0,msdos1)/PATH/TO/DISK.img
configfile (l,msdos1)/grub2/grub.cfg

By the way: Your disk image is still bootable in qemu, and could be made bootable in VirtualBox/VMWare too by constructing a suitable vmdk file.

Performance

Not great, because ntfs-3g is involved. Could be improved by calculating the image file offset on the disk and creating the loop device directly, but that is quite risky, especially when the image file is fragmented.