Linux – What are the nuisances of creating a bootable Windows 7 USB drive from linux with ms-sys or dd

bootable-medialinuxusb-flash-drivewindows 7

I have been reading some web pages and posts (here and in other forums) about how to create a Windows 7 installation USB media from linux (to install Windows 7)

I asked in TechNet about this, and I got a reply with general information on how to do it:

"I personally am not very familiar with
linux, but basicaly all that you need
to do… in whatever way you do it is
the following:

  1. Format a usb flash drive, either fat32
    or ntfs create a partition that is
    large enough to host the windows
    installation (give or take 3GB for
    64bit, aroudn 2.5gb for 32bit) and
    mark that partition as
    active/bootable. Since this can be
    done with windows, but just as well
    with a tool like gparted, you should
    be able to do the same in debian.

  2. Once you have created that partition,
    mount the iso that you download, and
    copy all files starting from the root,
    into the root of the usb flash drive.

That's all there's to it."

I found another method in various places, that is almost the same what was mentioned at TechNet. However, there seems to be a missing step in this method and/or a step that I'm not sure is necessary.

dd doesn't always work. Basically, the missing step was to write a proper boot sector to the usb stick, which can be done from linux with ms-sys. This works with the retail version of Windows 7.

Here is the complete rundown, see serverfault question for more details:

  1. Install ms-sys.
  2. Check what device your usb media is assigned ( fdisk -l ) here we will assume it is /dev/sdb.

  3. Delete all partitions, create a new one taking up all the space, set type to NTFS, and set it bootable:

    cfdisk /dev/sdb

  4. Create NTFS filesystem:

    mkfs.ntfs -f /dev/sdb1

  5. Mount iso and usb media:

    mount -o loop win7.iso /mnt/iso
    mount /dev/sdb1 /mnt/usb

  6. Copy over all files:

    # cp -r /mnt/iso/* /mnt/usb/

  7. Write Windows 7 MBR on usb stick:

    # ms-sys -7 /dev/sdb

  8. Make sure the write is flushed (be patient it can take a few minutes):

    # sync

  9. open gparted, select the USB drive, right-click on the file system, then click on "Manage Flags". Check the 'boot' checkbox, then close

…and you're done.

Questions

  • Shouldn't the usb work without doing the last step # ms-sys -7 /dev/sdb ? Or is it to make the usb bootable? Does it only to mark the partition as bootable?

  • Wouldn't it be better use rsync instead of cp -r ?

  • Do all this steps have to be done as root? If not, do I need to chmod all files to 664 and chown all the directories that are used to mount the USB device and the ISO image? I suppose that it's just easier to copy the data as root and it not affect the data.

  • Has anyone tried this method or some similar like copying the iso with dd ?

Best Answer

The ms-sys command is important. With the -7 option it creates a Windows 7 compatible boot sector on your flash drive.

You can't use dd because ISO's use an ISO Filesystem such as UDF or ISO9660, where-as your USB drive only properly supports disk file systems such as ext3, FAT32, or NTFS

Would be better use rsync instead of cp -r ?

Not really. cp -r works perfectly fine. Just realize that NTFS handles permissions differently to Linux, so using rsync to keep everything intact doesn't matter too much. All that really matters is that the files from the ISO are on the USB and that the boot sector is formatted correctly using ms-sys -7

You can do all the steps as root if you want. The only 2 steps that really require root are mkfs and the 2 mount's

If you're getting permission problems even as root, you may need to mount your USB using ntfs-3g /dev/sdb1 as some Linux Distributions only supply a Read-Only driver for NTFS.

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