A FOB STORY: some notes on bootable flash drives

Preparing the flash drive

It’s pretty easy to build single-boot flash drives – even for Windows 7 or 8.  They can serve as installers or as live devices that can run an OS or repair utility without being installed to a hard drive or SSD.   Drive formatting varies somewhat depending on whether it will be booted in legacy (BIOS) or UEFI mode or if it’s going to be a Windows flash drive.  I’ve found it’s almost always necessary to prep the flash drive, even if already seems to be formatted appropriately.  These things often come from the manufacturer with a strange formatting scheme.

I’ll give a generic example of drive prep using Windows 7 DISKPART.  This can also be done from Linux using any of several tools.  Run DISKPART from a command prompt.  This is an example and will look different on other machines.  The red (notes) aren’t part of the command line conversation and try to flag the different requirements for the two boot schemes – and offer a warning.  Please see below for details.


Microsoft DiskPart version 6.1.7601
Copyright (C) 1999-2008 Microsoft Corporation.
On computer: Z77

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online          238 GB      0 B
  Disk 1    Online          465 GB  1024 KB
  Disk 2    Online         1863 GB      0 B
  Disk 3    Online           29 GB      0 B

DISKPART> select disk 3  (note 1)
Disk 3 is now the selected disk.
DiskPart succeeded in cleaning the disk.
DISKPART> create partition primary
DiskPart succeeded in creating the specified partition.
DISKPART> select partition 1
Partition 1 is now the selected partition.
DISKPART> format quick fs=fat32  (note 2)
  100 percent completed
DiskPart successfully formatted the volume.
DISKPART> active  (note 3)
DiskPart marked the current partition as active.
DISKPART> assign
DiskPart successfully assigned the drive letter or mount point.

Notes: 1) Be absolutely certain you select the flash drive.  Otherwise you’ll b0rk one of your system drives.  2)  Use fs=ntfs when preparing a Windows 7  legacy boot installer.  Use fs=fat32 for Windows or Linux UEFI and Linux legacy booting. 3) The active command isn’t needed for UEFI boot (it won’t hurt anything, although it may confuse a UEFI+legacy BIOS into booting in legacy mode) but is necessary for legacy booting – either legacy only or UEFI and legacy.

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One Response to A FOB STORY: some notes on bootable flash drives

  1. Pingback: FOB Story II | GeezBlog

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