I have an external hdd with multiple operating systems on it (Ubuntu, Centos, etc). On newer computers, the drive is recognized as a USB HDD and I can boot it directly just fine.

However on an older computer, the BIOS allows me to boot from a USB key, but not a USB HDD. Go figure. The BIOS cannot be updated. Therefore I want to use the USB key like an intermediate BIOS, to redirect the boot to the USB HDD.

The bootloader on the USB key is UNetBootin but I cannot find the showcustom commands to boot to the external HDD. I don't need to install anything, I just want to find a way to boot to the Ubuntu partition (or any partition) on the external HDD.

Alternatively since the USB key boots into its own Ubuntu just fine, and sees all the partitions on the external HDD, can I somehow point to a partition and reload it?

I don't have grub


Have a look at Plop Boot Manager. It's a very small ISO, which you can burn to CD or USB, from which you can boot it.

Besides other things, it enables you to boot some devices which your BIOS can't. E.g. I use it to boot an Ubuntu USB on computers without the support of booting from USB devices. Before you boot Plop, make sure that USB Legacy Emulation is disabled in your BIOS setup.

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  • Thanks for the suggestion. It unfortunately didn't work, on two different computers. I did find the mysterious recovery partition for windows for the first time though, but otherwise it ignores the external HDD. This was tried with a standard USB 2.0 connection as well as a AKE esata/usb3 PCCARD. Both failed with Plop. Interestingly the external HDD works on USB 2 on one of the computers but not the other. Neither computer works with Plop at all. The Plop screen blinks and that's it. So it doesn't work with a known working system either. Don't know what I did. – sf2k Oct 16 '14 at 20:58
  • Separately, the esata/usb3 AKE pccard I have that doesn't load in windows works fine under Ubuntu! I just can't boot from it, as the driver is obviously not loaded yet. That's got to be a first that something works on Ubuntu but not Windows. This might be an avenue to pursue though. Maybe if I could just send ASMEDIA driver to UNetBootin or Plop or some other usb key iso boot manager and load the driver that might work. Any suggestions appreciated. ;) – sf2k Oct 16 '14 at 20:59

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