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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.

6 Likes

Fantastic!
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

What provides the isohybrid package? I’m thinking syslinux.

BalenaEtcher hasn’t failed me yet. Three-step bootable distro.

Balena sure works for me too. But it’s a close to 200M Download for something that i can do with no extra software in 99% of cases. Feels unnecesary.

I’ve run into problems with getting a working usb stick from both etcher and rufus in the past, on windows. Usually with debian based distros (OMV), which I think had something screwy going on with UEFI support, but to be perfectly honest the area of booting is all black magic to me so I have no good idea what the real problem was.

Fedora Media Writer was my solution. It also makes it easy to “reset” a usb stick back to normal.

I just ran into this issue using win32 on a Windows Server 2012 R2 IOS I recently downloaded. I had to burn the image to DVD to get it to boot. I thought it might have to do with using a USB 3.0 drive. I then tried a Ubuntu IOS on the same drive and it worked. What is the real issue and how do I solve it in windows? Should I try rufus or something other than win32?

Thanks John