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I have an Ubuntu 10.10 / Windows 7 dual boot environment. Occasionally, I want to boot directly off a USB stick or USB-connected portable HD and either by-pass the dual-boot GRUB loader or add a boot option for the bootable USB device(s).

Note: The USB boot option is set as a higher prior than the HD option in the BIOS, and the USB devices boot as expected in a single OS environment.

Problem: In a dual boot GRUB environment, the BIOS priority setting is essentially ignored.

What is the best approach to booting off a USB device in this scenario, adding "cdrom-detect/try-usb=true" to an existing GRUB entry...or another solution?

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The BIOS priority setting is not ignored. Your USB is likely registering as a HD in the BIOS - try reordering which HD device boots first (usually labelled USB-something) rather than setting USB to boot first.

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I don't think it has anything to do with dual-booting grub. I have Xp & Mint and I just tested setting USB as default boot entry and it worked. Maybe you should try restore BIOS setting and then give it another shot.

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The BIOS loads before grub, and it is the BIOS that selects the device to boot from, so it has nothing to do with grub.

That said, your usb device can register as a HDD (as another poster said). Quite often, you can press a button during the BIOS splash to select you boot device manually (often F12). I find this way easier, as it is the exception that I boot off a usb, and therefore don't want my computer to boot from it if I forget a usb key in there.

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Sorry, responded to the wrong response! Reposting...Thanks for your response. That makes sense for the occasional boot-up from a USB stick or portable USB drive. Is there a method, though, for adding an option line in the GRUB loader that directs the boot specifically to a named USB device? This is for use in an office environment where people would prefer to select their options from a menu. – Phil Hopkins Nov 26 '10 at 19:33

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