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I installed elementary os onto a usb using legacy settings, and I can boot it using legacy bios options. However, I would like to switch the boot to UEFI so that I dont have to change my PC's firmware setting everytime I want to boot windows from my hard drive, or switch it again when I want to boot elementary off the USB. Is this possible, and how would I go about doing it?

marked as duplicate by muru, sudodus, Zanna, Eliah Kagan, Eric Carvalho Sep 23 '17 at 12:15

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • What kind of install is on the USB? Live, Persistent or Full install? If you are using a Persistent install, you can save your casper-rw file to your windows desktop, do a UEFI install and replace the casper-rw file when done. You may need to add the word "persistent" to your boot configuration. – C.S.Cameron Sep 23 '17 at 15:18
  • Not sure what this question has to do with the "duplicated" question, which concerned switching the internal drive to UEFI, this question concerns getting a USB drive to boot UEFI. – C.S.Cameron Sep 23 '17 at 16:01
  • For a UEFI only USB device you can simply extract the Ubuntu ISO to the FAT32 formatted USB device using 7Zip and set the boot flag. Add your casper-rw file and the word "persistent" before "quiet splash" in /boot/grub/grub.cfg. – C.S.Cameron Sep 23 '17 at 16:18
  • Ben Sakac, are you asking about an installed system (installed like into an internal drive, but into a USB drive) or about a live or persistent live system)? -- If a live or persistent live system, @C.S.Cameron's comments are relevant, and marking it 'duplicate' is wrong. – sudodus Sep 23 '17 at 16:22
  • @sudodus it is an installed system, but it is installed on a usb as opposed to an internal drive – Ben Sakac Sep 23 '17 at 20:26
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If a live or persistent live system

@C.S.Cameron's comments are relevant.

  • Save the casper-rw file or the content of the casper-rw partition.

  • The method he is describing is explained with more details at the following link,

    https://help.ubuntu.com/community/Installation/iso2usb

  • If you want a persistent live system with a casper-rw partition, you can use mkusb to create it from the same Ubuntu iso file as the previous one. Then the content of the old casper-rw partition will work.

If an installed system (installed like into an internal drive)

It is possible to convert the boot mode from BIOS (alias legacy) mode to UEFI according to this link (as suggested by @MichaelBay in the comment to your question),

Which commands to convert a Ubuntu BIOS install to EFI/UEFI without boot-repair on single boot hardware?


An alternative (for other users, who read this in the future) is to create an installed system (or modify your current system) such that it can boot both in UEFI mode and BIOS mode. See the following link,

help.ubuntu.com/community/Installation/UEFI-and-BIOS

This way you make a system, that is portable between newer and older computers.

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    It does not sound like the op needs BIOS mode, only to boot the USB in UEFI mode, so he does not need to adjust the computer each boot. – C.S.Cameron Sep 23 '17 at 15:59
  • @C.S.Cameron, You are right. I was thinking about other users, who might benefit from the alternative. But it can be misunderstood. After a short time (enough to let you read this) I will remove this answer. – sudodus Sep 23 '17 at 16:09
  • Thanks Sudodus, I'm wondering how this question got marked as duplicate? I think this would be the perfect question to propose The Simple Method. – C.S.Cameron Sep 23 '17 at 16:21
  • Until we know better, I edited my answer to add a paragraph (if the original question is about live and persistent live system). – sudodus Sep 23 '17 at 16:39
  • @sudodus I have an installed system on 32 GB pendrive. What you describe, modifying my system to be able to boot in BIOS and in UEFI sounds like what I want, but the link you provide for that seems to be for creating an install in this way, not modifying a current system to be able to boot in both modes? – Ben Sakac Sep 23 '17 at 20:38

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