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I'm not new to Ubuntu (have been running linux since the 90's) but now that I'll upgrade my computer to a new one again I'm wondering a bit about UEFI and Legacy boot.

On the whole, it seems that it is more 'modern' to run on UEFI than Legacy and that it will be phased out at some point later. So I'm thinking of switching to UEFI, but I do NOT want secure boot. I don't use dual boot though with Windows.

Now I wonder several things: Is it possible to run UEFI without secure boot, and if so, how do I set it up? Has so far always run Legacy.

I will have an ASUS TUF X570-plus motherboard with the latest BIOS software.

Wondering if it's as simple as disabling CSM in Bios to have UEFI fully. And to put 'Other OS' under the secure boot settings, does this turn off secure boot, or do I also have to delete the PK key under 'Key management'?

I do not think there is any way to directly disable secure boot though in the BIOS.

Would like an explanation of what settings are needed in an ASUS BIOS to use UEFI without secure boot.

Will use Ubuntu 20.04 on the new computer.

Thanks

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  • We test Lubuntu with both BIOS/legacy, uEFI & Secure uEFI. I use the same hardware in testing both uEFI modes (changing a setting in the machine uEFI/setup) as do others so yes you can use uEFI without secure uEFI (if your hardware/firmware allows it). Some hardware allows you to flip to BIOS/legacy or uEFI and/or Secure-uEFI, others do not (some hardware I have I can only use for uEFI/Secure-uEFI QA-testing). Note: I"m using Lubuntu as example; the same hardware is also used to test Ubuntu, Xubuntu... It's largely firmware specific in my experience.
    – guiverc
    Jun 22, 2021 at 9:15
  • In better UEFI BIOS you may simply add/install your own custom key for a "secure" OS. Otherwise you may simple deactivate secure boot in your UEFI BIOS.
    – paladin
    Jun 22, 2021 at 9:56
  • Thanks for the comments. But I also wondered how this can be done when there is no special button to disable secure boot but must be done in another way. Perhaps the best thing is to ask on an ASUS forum. I also do not really know what is the most common way 2021 to install Ubuntu, in UEFI or Legacy. Maybe continue with Legacy, but it's not really future-proof.
    – pelm
    Jun 22, 2021 at 15:02
  • My older Asus x97 said to change to "other OS" if installing Windows 7, as Windows 7 did not support UEFI Secure Boot. So that is really the Secure Boot on/off setting. While much older, Asus uses similar screens with newer systems. Asus-ar screenshots oldfred ubuntuforums.org/showthread.php?t=2258575&page=2 I had to save screens & list of settings as every UEFI update reset to defaults & I had to redo most of them. It only remembered boot entries in UEFI and boot order.
    – oldfred
    Jun 22, 2021 at 15:59
  • But are the preferred way of installing Ubuntu 20.04 under Legacy BIOS? Or is it with UEFI nowadays?
    – pelm
    Jun 22, 2021 at 18:25

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