Making a Bootable Windows Install Flash Drive in Linux

2013-11-13

Making a bootable flash drive for installing Windows is a bit more involved than you would think, but it’s still easy. Making a bootable linux flash drive is as simple as using dd to write the iso image directly to the flash drive. Here are the steps involved to make it work with a Windows install.

Partition the drive.

Create a single NTFS partition on the drive, and make it bootable.

sudo fdisk /dev/sdc

Assuming /dev/sdc is your flash drive of course.

In fdisk, first do o to create a new empty partition table. Second, n to create a new partition. Use the defaults for anything it asks. Then t to change the type. Change the type to 7 for NTFS. Last step is a to make the partition bootable. Then w to write the changes to the drive.

Format and copy data.

Now that the drive is partitioned, it’s time to create an NTFS filesystem and copy the data over.

sudo mkntfs -f -L Win7 /dev/sdc1

The -f option is for fast format. Otherwise it writes zeroes to the whole drive. We don’t want to wait for that. The -L option allows you to specify a volume label. Make it whatever you want. Enclose in quotes if you want spaces in your label. Personally I avoid spaces whenever possible. Finally /dev/sdc1 is the partition we created with fdisk.

Next you will need to copy the contents of the install disc to your flash drive. I usually mount the iso as loopback, but of course a physical disc will work just as well.

Create directory to mount to if using loop.

mkdir loop

Mount the iso.

sudo mount -o loop windows7.iso loop

I usually just unplug and replug the flash drive so it will automatically mount. Then copy the contents over.

rsync -av loop/ /media/win7/

Where loop/ is where the iso or disc is mounted. The trailing slash is important. And /media/win7/ is where the flash drive is mounted.

After it’s done copying, you can unmount the flash drive and iso or disc.

sudo umount loop
sudo umount /media/win7

Write a bootloader.

The last step is to use ms-sys to write a bootloader to the flash drive. You can download the source code from their website.

http://ms-sys.sourceforge.net/

Download and compile it. You shouldn’t need to install any dependencies.

Finally, the command to write the bootloader.

sudo ms-sys-2.2.1/bin/ms-sys -7 /dev/sdc

Note that here I’m running the ms-sys binary directly from the tree the source was extracted to, without installing it on the system. If you install it, replace ms-sys-2.2.1/bin/ms-sys with ms-sys.

The -7 option is for a Windows 7 bootloader. You can use -m instead for an XP bootloader.

That’s it. You should be able to boot from the flash drive and install Windows much faster than from an optical disc.