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Booting the Computer from USB

Remove all unneeded USB items, but keep the network cable attached.

Boot menu

Instead of editing BIOS settings, you can choose a boot device from the boot menu. Press the function key to enter the boot menu when your computer is booting. Typically, the boot screen displays which key you need to press. It maybe one of F12, F10, F9.


Insert the bootable USB flash drive that you just created in your target computer and restart it. Most newer computers can boot from a USB flash drive. If your computer does not automatically do so, you might need to edit the BIOS settings.

Restart your computer, and watch for a message telling you which key, hotkey to press to enter the BIOS setup.

  • It will usually be one of F1, F2, F9, F10, DEL, Enter or ESC.
  • The hotkey should be described in the user manual provided by the manufacturer of the computer (a printed or electronic document).
  • You can also search your hardware on

Press this hotkey continuously or tap repeatedly (different between computers) while your computer is booting to edit your BIOS settings. (On HP Mini Netbooks, the correct key is usually F9.)

Edit the BIOS settings

Select 'hard disk/USB-HDD0'

Note: with some motherboards you have to select 'hard disk/USB-HDD0' to choose the USB flash disk. It may work like this because the system sees the USB drive 'a mass storage device' as a hard disk drive, and it should be at the top of the boot order list.

So you need to edit the Boot Order. Depending on your computer, and how your USB key was formatted, you should see an entry for "removable drive" or "USB media". Move this to the top of the list to make the computer attempt to boot from the USB device before booting from the hard disk.

Normally you would enter into the BIOS/UEFI menus directly at boot as described above, but if you are running Windows, you can also get there according to this link.


The 40_custom method

In the particular case, that you have linux and grub installed there is also the 40_custom method. Some pendrives boot from grub even if they won't boot from the computer's own BIOS USB boot menu entry. See the following link for a background about grub Scripts: /etc/grub.d/

Edit the file

sudo nano /etc/grub.d/40_custom

Add the following text to the file 40_custom (notice that it is important to keep the first lines, that come with the file)

menuentry "External drive (on hd1) if no eSATA drive connected. edit if necessary" {
        insmod part_msdos
        insmod part_gpt
        insmod fat
        set root='(hd1)'
        drivemap -s (hd0) ${root}
        chainloader +1

and run the command

sudo update-grub

Then you will get a grub menu option to boot from a second drive (hd1), which could be a USB pendrive. If another drive is hd1, you can edit the line to (hd2) etc.

If there is no grub menu, press the left shift key during boot, and it should appear.

This chainloading method does not work in UEFI mode.

The Chainloader

This method is developed into a method to boot the computer with one USB drive that is a good booter, and chainload to another USB drive, where the operating system resides. See this link Howto help USB boot drives

PLoP Boot Manager

  • For old computers that cannot boot from USB. Some computers can see the USB flash drive and may have the option to boot from USB but cannot actually do so. All hope is not lost.


Just follow the instructions on the PLop website.

A detailed guide to make Plop Boot Manager work from GRUB by installing it on hard drive is available here -

Flow chart for trouble-shooting

There is a flow chart for trouble-shooting and corresponding lists of possible causes of problems to boot from USB at the following link,

Why Doesn't a Bootable USB Boot

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Installation/FromUSBStick/bootUSB (last edited 2020-07-29 13:21:38 by nio-wiklund)