[oclug] Re: Bootable flag on USB drive?
andycivil at gmail.com
Fri Feb 6 22:06:35 EST 2009
Update. I've read man syslinux, used the package manager to get gparted on my
Ubuntu. I can see the boot flag with gparted. It seems like on this one
computer, unetbootin will boot, and syslinux won't. Don't know why.
Andy Civil wrote:
> I confess to being a bit frustrated here. I've made a bootable USB flash
> drive according to these instructions:
> but it won't boot. It doesn't even try to boot. Another bootable drive
> in the same computer boots OK (puppy linux).
> I don't know how to debug the existence of an MBR or a bootable flag on
> this drive, to identify what is wrong.
> The windows tools that I use for CD's that will handle boot records
> (e.g. magicISO) don't seem to work on flash drives.
> The windows disk management tool (diskmgmt.msc) doesn't even mention
> The Ubuntu disk tool doesn't mention boot sectors or bootable flags either.
> I recall that I can at least see the bootable flag in fdisk or cfdisk,
> but neither will work on the flash drive, as far as I can tell. If I say
> "cfdisk /dev/sda" it gives me an error, and if I eject the drive but
> leave it physically plugged in, it still gives me an error.
> Does an ISO file include the boot record? It seems that if I use one of
> the windows tools to extract an image, it's not included; but if I
> deliberately suck the boot record off the CD (in this case) then I can
> store it in the ISO. Is that because the boot code is dependent on the
> medium, and the ISO should be medium independent?
> Does a USB flash drive even have a bootable flag?
> Are there any key words that I should be googling for (e.g. go look up
> 'syslinux')? What tools (Ubuntu or XP) could I be using to view/check
> this stuff?
> Any basic tutorial on boot sequence would be handy; I think the BIOS
> checks for the bootable flag on the drives listed in the boot order,
> then loads and executes code in a specific location (MBR?) which is not
> a file, per se. MBR code loads and runs a specific file, or possibly
> reads some config file and loads whatever's listed there. Am I right?
> Hints welcome.
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