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How to make sure your bootable USB from ISO will actually boot


Have you ever tried “burning” an ISO to a USB device only to be frustrated that IT. JUST. WON’T. BOOT? Here’s how to check if the ISO will be bootable on USB, and how to fix it if it won’t.

Two simple steps:

  1. Check with file if the ISO is a hybrid.

    file [/path/to/ISO]

    If it’s a hybrid, the output will look something like this and the USB should be bootable:

    [/path/to/ISO]: DOS/MBR boot sector; partition 2 : ID=0xef, start-CHS (0x3ff,254,63), end-CHS (0x3ff,254,63), startsector 268, 0 sectors

    If it is not a hybrid, you can expect to see something like this which likely won’t boot from USB:

    ISO 9660 CD-ROM filesystem data '[LABEL]' (bootable)
  2. Make the non-hybrid ISO a hybrid:

    isohybrid [/path/to/ISO]

    Or use flag -u or --uefi to make it UEFI bootable:

    isohybrid -u [/path/to/ISO]

That’s it! Just use your preferred method to get the ISO onto the USB device, such as Gnome Disks, or sudo dd bs=4M if=[/path/to/ISO] of=[/path/to/USB] conv=fdatasync, and enjoy booting.


The small linux problem thread

I’ve run into a couple of distro’s that refused to work with DD, and I’m hoping this magic ju-ju might spare me from having to run random media creation toolkits