[oclug] Re: Bootable flag on USB drive?

[Andy Civil]

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


Andy Civil wrote:
> I confess to being a bit frustrated here. I've made a bootable USB flash 
> drive according to these instructions:
> http://www.pendrivelinux.com/ubuntu-810-install-using-the-built-in-usb-installer/ 
> 
> 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 
> bootable.
> 
> 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.
> 
> Thanks
>