Knowing how to boot from a usb key or an external hard drive can allow you to install an operating system on a computer without a CD / DVD drive, or allow you to use a “live” system. The method described here involves entering BIOS and changing the order of the boot sequence.
Boot from a USB key or hard drive
In general, booting from a USB stick or hard drive is possible on all computers less than ten years old. The most recent computers allow you to boot directly from a USB volume in an automated way, but if you are reading this article, it is probably because at home, in fact, it is not automatic …
If you are on Mac follow this tutorial to create an OS X USB drive and boot from it. We will therefore have to change the order of the boot sequence via the BIOS.
- Switch off your computer: on some machines, it is not possible to access the configuration screens of the BIOS when restarting.
- Turn on your computer and observe what is displayed on the screen: somewhere a message similar to this is displayed
- In this case, press the DEL (Del). That could very well be another key – and sometimes there just isn’t a message: in this case, do a glissendo with the finger of the button ESCAPE at the touch F12 just after ignition!
- You should see a screen similar to this one in front of you
- If you are lucky, the section Boot will be visible as soon as you enter the BIOS
- Navigate to the section Boot with the right and left arrows of the keyboard
- You now have access to the boot sequence
- In this case, to boot from a USB volume, just put + Removable Devices at the top of the list. In other cases, the configuration can be more explicit: all you have to do is bring up “USB”
- When finished, insert your key into a USB port, then press the key. F10 then Y to exit and save the changes.
BIOS models are plentiful, and yours might give you a bit more of a problem. Do not despair ! On the contrary, navigate in the BIOS menus which are not so numerous in the end.
The list system is generally the same on PCs (a semblance of standard, just like the F10 key to save and exit): the devices at the top of the list take precedence over the next ones, in order. Finally, follow the instructions built into the BIOS – they’re here to help you better understand how it works!
What if you are using UEFI instead of BIOS?
If this method does not work, and you are on Windows 10, it may be because you are using UEFI instead of BIOS. It is still possible to change the Boot sequence, but the method is different and perhaps less intuitive.
- Close your session
- From the login screen, press the button to display the options for shutting down or restarting the computer.
- By holding the key Shift. pressed, click To restart
- A menu will appear when restarting: click on Troubleshoot> Advanced options> UEFI settings
- The computer will restart again
You should now see a screen with options similar to the Bios described above. You can then change the boot order as if it were a question of BIOS! A faster method is to choose your boot device without changing the Bios or UEFI settings. It is also the most suitable method if you want to boot on a USB key or external hard drive on an ad hoc basis.
In this case, there is no need to permanently disrupt the order. Here too, you have to press a key very quickly after switching on the PC. Usually this is the F2 or F10 key.. If one of the two does not display the choice of boot device screen, try the other keys between F1 and F12 or check the manufacturer’s website.