Usage Notes

Pete Batard edited this page Sep 3, 2015 · 9 revisions
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Rufus usage notes

The goal of this page is to provide answers and details on topics that aren't really suited for the FAQ.

Table of Contents


Why the increase in size between Rufus 1.4.12 and Rufus 2.0?

Rufus 2.0 adds the following features:

  • Grub 2.0 support (including Grub 2.0 system files)
  • Grub4DOS support (including Grub4DOS system files)
  • Windows To Go support
  • Decompression of .Z, .gz, .bz2, .xz and .lzma image files
  • additional translations
  • new messages for existing translations, including fairly verbose messages aimed at clarifying Windows To Go restrictions
It also upgrades Syslinux from 5.10 to 6.03, which is much bigger in size.

Considering this, the size increase is actually quite minimal for the amount of new features that were integrated.

Windows To Go

Why do I need Windows 8 or later to create a Windows To Go drive?

Unlike regular ISO → UFD creation, where one can just extract the ISO files, the creation of a Windows To Go drive requires the application of a Windows Image (sources\install.wim), which is a completely different process from a regular extraction. Because there is no small sized Open Source library that does WIM image application, we are forced to use the WIM API from Microsoft.

Moreover, the Microsoft WIM API requires the install.wim image to be accessible as a regular file before it can process (we can't just point the WIM API to the ISO, or part of the ISO that contains the image), which means that, to be able to do that without having first to extract a ~4GB file to a temporary drive (and make sure it gets deleted when we're done with it), we need the capability to mount an ISO as virtual drive, which is something that only Windows 8 and later offers natively (and of course, there again, there are no Open Source solutions we can use to create a virtual drive). Because Windows 7 and earlier do not provide native ISO mount capabilities, we simply can not support these OSes at this stage.

Can I create a Windows To Go drive using a Windows 7 ISO?

Yes. But as explained above, you will only be able to create a Windows 7 To Go drive in Rufus is you run it on Windows 8 or later.

What partition type and target should I use when creating a Windows To Go UFD

  • If you want _Restricted_ Boot (a.k.a. Secure Boot), you should use GPT for UEFI. This will create a drive that can only be booted on an UEFI computer, in UEFI mode, and that uses a boot chain that should be signed by Microsoft all the way. Note that this mode definitely requires a FIXED USB drive.
  • If you want dual BIOS + UEFI boot, you should use MBR for BIOS + UEFI. This mode also allows you to use a REMOVABLE USB drive (though I have had ZERO success booting from REMOVABLE - Only FIXED drives seem to work with Windows To Go).
  • If you want to boot in UEFI mode, but don't care about Secure Boot and want minimize the wastage incurred by the MSR and EFI partitions (as well as try your luck with a REMOVABLE UFD), you should use MBR for UEFI.

What's the deal with the MSR on Windows To Go GPT drives?

Due to an antiquated boot process that they are too scared to change (namely hiding stuff in the hope users won't notice it), Microsoft requires every GPT drive that Windows will run from to have an MSR, so we follow suit. Note that Windows installation GPT media don't have this requirement (since they don't run Windows but merely install it). Read more about MSR here.

What's the deal with the EFI system partition on Windows To Go GPT drives?

The UEFI specs hint (but aren't entirely explicit) that a FAT32 partition should be used for FIXED media to boot stuff in EFI mode. And indeed, Windows To Go will not boot on GPT drives unless you installed BCD on a FAT formatted EFI system partition (which should be created without a label!). But then that means you are restricted with the FAT32 minimum partition size, which is tied to the minimum cluster size that you can create a FAT32 FS with which itself is tied to the disk sector size. This means for instance that, for a 4k drive, you must create a ~300MB EFI system partition if you want to be able to format it as FAT32.