Ubuntu – Doesn’t a Bootable USB Boot


This question is asked often in Ask Ubuntu, sometimes with few hints about the situation.

Please provide a list of possible reasons to help troubleshoot the problem.

Best Answer

  • I know from experience that if a GUI USB creator like Rufus or Startup Disk Creator doesn't work then dd won't work either for the same (usually hardware-specific) reason. Sometimes it is possible to troubleshoot why a bootable USB doesn't boot if it is hardware specific (see below screenshots). For example, safe graphics is not working is a clue to an underlying hardware-specific problem. In this case enabling the nomodeset kernel boot option might work. Otherwise it is often possible to circumvent a hardware issue by installing Ubuntu using the lightweight, text-based Ubuntu minimal CD/USB.

    More reasons not on the original list:

    1. Bad USB flash drive. This could even be a new flash drive which I assume to be not corrupted. Ubuntu will boot after making the Ubuntu live USB on a different USB flash drive. It's worth a try if you have two or more USB flash drives.

    2. Reformat the flash drive and reload the Ubuntu ISO from an application for making a live USB.

    3. Voltage irregularities that affect the smooth amount of voltage delivered from the motherboard to the USB flash drive. Possible causes of this are motherboard, power supply and even irregular house current. A very old computer is more likely than a new computer to have issues with the motherboard or power supply that affect booting to a live USB session.

      Here are a few suggestions that worked when I tried them.

      1. Don't plug in USB devices like mouse and keyboard next to each other. Plug in one USB device at the front and one at the back.

      2. Disconnect unnecessary devices when booting the USB to reduce the power load, for example disconnect one HDD if there are two drives. If you have a 4-port USB splitter with switches on each port this is ideal, because you can turn the USB mouse off when you don't need it and you don't need to open the computer case to disconnect an internal drive in order to reduce the power load.

      3. The Ubuntu live USB will sometimes be able to boot if the same computer is moved to another location that has a more controlled source of current or connected to an uninterruptible power supply (UPS).

    4. Overheating may cause the computer to power off when trying to start the Ubuntu installer. The CPU temperature can be checked by accessing the UEFI/BIOS setup utility when the computer is booting.

    5. Some applications for making Ubuntu live USBs seem to work better than others. For example, the built-in Startup Disk Creator application is better than most.

    6. In case the BIOS Boot options do not recognize the USB device at all, some older BIOSs do not even correctly label USB flash drives in the Boot options. Instead they use some non-standard nomenclature for flash drives like USB-FDD or USB-HDD. USB-FDD stands for "floppy disk drive" which never works with USB flash drives, so in this case you should choose USB-HDD instead. Even though a USB flash drive is not a hard disk drive choosing this option frequently works.

    (Click images to enlarge)