I've got a dual boot Ubuntu18.04/Win10 system with the BIOS set to 'Legacy Boot'. I can boot fine into this system. However my mkusb live USB (also 18.04 with persistence) won't boot if I leave the BIOS in 'Legacy Boot' mode.

I can swap the BIOS toggle to 'UEFI Boot' and my mkusb live USB will proceed to boot without issue. When I try to boot normally to Ubuntu/Win hard drives the system throws an error along the lines error: no operating system, and I have to change the BIOS back to 'Legacy Boot'.

What is going on with my system?

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    Are you using default settings in mkusb? does the drive work on other computers in BIOS and UEFI? – C.S.Cameron Feb 12 at 3:11
  • Is this in your hp computer? In that case it could be a problem, that is typical for some hp computers: they are unwilling to boot USB drives via grub in BIOS mode, if there is a GUID partition table, GPT. -- You can make a persistent live drive with the MSDOS partition table (which is not the default setting), and try it in your computer. – sudodus Feb 12 at 7:48
  • @C.S. Cameron I am using the dus command of mkusb and utilize all the default settings. On other computers this mkusb live USB will boot in either UEFI and Legacy modes. @sudodus this is different than the other issue I posted. This is a different computer. – Jason Hunter Feb 13 at 3:24
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    I had a similar occurrence the other day, the persistent drive had the word persistent in the grub.cfg file but would only boot UEFI. I also added the word persistent to /isolinux/txt.cfg and it booted in BIOS OK after. – C.S.Cameron Feb 15 at 5:12

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