I installed a Linux distro on an external hard drive mounted on a USB 3.0 adapter. I could boot from the external hard drive before disconnecting the adapter from my computer. Currently the external HDD:

  • doesn't show up in BIOS/UEFI settings (and as a consequence I can no longer boot the Linux operating system from the BIOS menu),
  • doesn't show up in Windows Explorer,
  • shows up in Windows Disk Management utility, but none of the partitions can be formatted.

How do I make this external hard drive useful again by either:

  • making it detectable from within the BIOS/UEFI settings and menu, or
  • formatting it as an external storage device?
  • Are you still able to select the [your Linux OX here] EFI entry? Where exactly is your ESP (EFI System Partition) located, in the external HDD itself or any other internal drive (the more typical scenario)? Are the EFI files pertaining to to OS installed in the external drive still there?
    – user772515
    Commented Apr 29, 2018 at 23:27
  • @MichaelBay The external HDD had a partition labeled EFI [something]. I pressume this ESP was located in the external HDD.
    – useranonis
    Commented Apr 30, 2018 at 8:10

1 Answer 1


Formatting as an external storage device

There are free, third-party, disk management utility software that are typically able to format a drive when Windows Disk Management utility can't. If it shows up in Disk Management utility within Windows, it'll probably show up in one of these apps. Begin by installing one of these apps. From there format the drive in a file system, if you can, taking care to choose a file system format that is both compatible with Microsoft Windows and admits large file sizes (suitable for a large external memory). The external hard drive doesn't show up in Windows Explorer because none of its partitions, it seems, are now compatible with Microsoft Windows after installing the Linux distro.

Making it detectable via BIOS/UEFI settings and menu

Here I'll leave my answer incomplete in wait of a knowledgeable expert to contribute. (As a «quick fix»: I recommend installing the Ubuntu Linux distro preferably to the external HDD in order to mitigate the prospect of that problem. I did not have the same problem with Ubuntu 18.04 LTS installed on the same external HDD).

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