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Thread: Howto Flip Removable Media Bit (RMB)

  1. #1
    Join Date
    Jul 2007
    Ubuntu Development Release

    Howto Flip Removable Media Bit (RMB)

    I bought a 16GB PNY SD card to use on my Dell mini. It works fine in Ubuntu (naturally) but I want to switch the Removable Media Bit (RMB) so that windows will see it as a fixed disk. This allows multiple partitions to be visible and configurable in Windows.

    I have googled extensively, and found only the Lexar Bootit utility (didn't see my SD card). Surely there has to be a way to do this in linux. Perhaps even just dd'ing /dev/zero to the whole drive?

    The RMB is apparently the 7th bit of the first byte on a disk. It needs to be 0 for a fixed disk.

  2. #2
    Join Date
    May 2008

    Re: Howto Flip Removable Media Bit (RMB)

    You know 20 years ago I think I could have pulled that off in DOS with a good hex editor but not anymore. I would like to know if you find a way.
    Ultimate Edition Links

  3. #3
    Join Date
    Apr 2007
    Eastern USA

    Re: Howto Flip Removable Media Bit (RMB)

    No one?

  4. #4
    Join Date
    Jun 2010

    Re: Howto Flip Removable Media Bit (RMB)

    I know how to do that and the cause of the problem ..
    On all windoze-OS a disk that has the RMB set to "1"(actually it seems like m$ and the chip-mfg's don't always agree on this !)
    will be identified as a "removable disk" and windoze does not allow multi-partitioning of "removable disks"
    or accessing more than the first partition by design .

    Linux doesn't care about this, neither does your BIOS .
    It's probably designed that way because windows previously didn't create properly aligned partitions
    and this has a noticeable negative performance-influence on all flash-based media ..
    Besides, on flash-media partitions don't "exist" in the same physical manner as they do on a "normal" HDD,
    the data is all over the place, being moved around by wear-levelling and all the other neat tricks controllers have up their sleeve
    to allow the use of inferior MLC -flash . Some of these controllers are Multi-lun capable btw.. That's even better !!
    You could have up to 8 primary partitions on one of those .
    Anyway, it's done "in hardware", this isn't correct :
    The RMB is apparently the 7th bit of the first byte on a disk.
    The RMB does not reside on the disk, it's coded in to the controller .
    The removable media device setting is a flag contained within the SCSI Inquiry Data response to the SCSI Inquiry command.
    Bit 7 of byte 1 (indexed from 0) is the Removable Media Bit (RMB).
    A RMB set to zero indicates that the device is not a removable media device.
    A RMB of one indicates that the device is a removable media device.
    Drivers obtain this information by using the StorageDeviceProperty request.
    Some cards (and/or readers) can present the media as a "Fixed" disk to windows,
    allowing multiple,usable partitions, but usually it's hard finding the software that allows
    "flipping the removable media-bit" .
    It is worth going through the trouble of finding the tools for doing this in hardware,
    if possible, because it will work on all windows-machines .
    The HID/PID of your controller may lead to something useful on google

    In case the specific card/controller you use can not be "flipped" in hardware
    there are also a couple software-solutions,
    the "Hitachi Microdrive Filterdriver"
    or "dummydisk.sys"
    Your device(s) will need to be configured to use the Hitachi-driver whereas "dummydisk.sys" makes all "removable disks" "fixed" ..
    There's a very good guide on how to configure the Hitachi-driver available here :

    Obviously, this will only work on boxes that have either driver installed and
    admin-rights are required to install ..

    Hope that helps you out ..
    Last edited by Peter Peterssonn; June 5th, 2010 at 10:49 PM.

  5. #5
    Join Date
    Jan 2011

    Re: Howto Flip Removable Media Bit (RMB)

    Incredibly sorry to dig up an old post, but I've seen some questions on how to do this in linux out on the interweb.
    I think that simply using DD will produce the desired results. A bit of a hammer approach, but can be narrowed down. You don't need to wipe the whole disk, just the first byte.
    dd if=/dev/zero of=/dev/sdx bs=1 count=1
    That should do it. I had a big fat32 partition on mine when I did it and I don't appear to have suffered any data loss.

    Again, sorry for digging around in a graveyard.

  6. #6
    Join Date
    Jul 2011

    Re: Howto Flip Removable Media Bit (RMB)

    Yours is an Excellent thread. Most other web articles cite WINDOWS OS tools (1) BootIt - Lexar USB Flip the Removable Media Bit Tool from "" and (2) HP USB Disk Storage Format Tool from "". Neither tools changed the Windows OS Recognised Removable status in my USB Pen sticks.

    This article seems to be more universal, even if Bit 7 RMB only refers to some USB pen sticks / Flash Drives without Controller supplied RMB.

    It seems to me if one can distinguish the two implementations, one can see if the Linux / cygwin (Unix OS) dd method will work.

    Does anyone know how to distinguish pen drives with CONTROLLER emulated RMB from Implementations with explicit Bit 7, Byte 1 ?

  7. #7
    Join Date
    Jul 2011

    Re: Howto Flip Removable Media Bit (RMB)

    It occurs to me if one completely obliterated the Media Byte 1 with all zeroes using dd, could one lose access to the entire drive ?

    Could some Host OS fail to distinguish the now ‘all zero’ USB Stick media byte from say a USB mounted Floppy disk ?

    Perhaps some caution is required here. Fortunately, the dd command had no effect on my USB pen Sticks regarding use and Removable Status.

  8. #8
    Join Date
    Nov 2011

    Talking Flip Removable Media Bit (RMB)

    Quote Originally Posted by 2hot6ft2 View Post
    You know 20 years ago I think I could have pulled that off in DOS with a good hex editor but not anymore. I would like to know if you find a way.
    I got myself a good Hex Disk Editor (HxD)
    How could I flip it (cannot work out how to find bit 1 of byte 7)

    (I am new to Hex Editing)


  9. #9
    Join Date
    Jun 2006
    Ubuntu 16.04 Xenial Xerus

    Re: Howto Flip Removable Media Bit (RMB)

    Old thread. Closed.

    @saleemrashid1, the software you link to runs only in Windows. This is an Ubuntu forum. If you need help running a Linux hex editor please start a fresh thread.
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