GPT, MBR, UEFI, and Secure Boot

Discussion
1

I believe I know the definition of all 4 of them. Yet I get confused,
The desktop I am working on is UEFI and secure boot. I go to boot a Ventoy USB and it will not boot unless I turn off UEFI and secure boot. I get the same problem with Clonezilla.

When installing MX from the Ventoy UBS, I get a warning that my PC may not be boot-able if I proceed.

Then my PC would not boot until UEFI and secure boot was turned back on. I don’t understand why my PC cares about a bootable USB drive.

I don’t believe I have seen where I can make a UEFI boot USB for Ventoy or Clonezilla if that’s is the problem. Also I believe a disk has to be in the format of GPT to have UEFI.

My sda1 partition is /boot/efi and partitions are GUID Partition Table.

What am I doing wrong?

Update;
I used this same Ventoy USB on my laptop which I thought was UEFI and had no problem booting it nor a problem with the MX install. But maybe it is not UEFI? The 1st partition is
/media/easyt/5673-CF1B and inside that partition is a folder called EFI.

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Does this or will this tie in to my question for the bios update in jure

Glad you asked as I changé these to get something to boot then if it works leave alone, if not change it back after an install. Dont use ventoy as I broke the usb, stood on it by accident, I tend to have at least one key for each version of mint, due, mate, 32bit etc

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Howard, I think the first thing to do is to take Ventoy out of the equation.
Can you make a plain usb drive of MX with dd

dd if=xxxxxx.iso of=/dev/<name of usb drive> conv=fsync

Then try to install MX from that.

If a disk has a GPT partition table, one can

  • use UEFI boot provided the disk has an EFI partition containing grub
  • use legacy boot provided the disk has a BIOS BOOT partition containing grub

If a disk has an MSDOS partition table, one can

  • use legacy boot with grub written to the MBR

I am not sure how/if secure boot interacts with the above

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UEFI vs Legacy Bios (~MBR)

UEFI- Secure boot On or Off- If it is On computer firmware checks boot-loader (on booting device) it looks to see if it was signed by a trusted key before allowing boot. The Trusted keys are in computer firmware (You can add keys to the firmware)

Many UEFI boot-loaders (booting device) are unsigned or self-signed -If not signed by trusted key, secure boot will not work.

GPT is effectively required for reliable UEFI booting on internal system drives.

USBs do not necessarily have to be GPT, they can be MBR. Most UEFI firmwares are very flexible with USBs. They look at a fallback path: \EFI\BOOT\BOOTX64.EFI (which exist on a FAT32 partition)

USBs CAN also be hybrid and support both MBR or UEFI - They include both sets of boot components, so the firmware picks the one that matches its current mode.-

Personally, I like UEFI but I do not use secure boot. Makes life a lot easier (more flexibility). In my case, pros outweigh cons.

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You can do that on a hard disk too. I have a hybrid internal hard disk … I can boot it with either legacy of uefi. It has a GPT partition table and it contains 2 copies of grub … one in the ESP partition and one in the bios-grub partition.

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Something was strange with my laptop and the live MX ISO. After I booted the ISO and selected which MX I wanted to install, MX could not find the USB. I was able to solve that problem by loading the MX ISO onto a Ventoy USB.

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Well, that is part of my confusion. I thought secure boot was required with UEFI.

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8

Switch it off, if it works thats the answer,

if not

Switch it on if that works you have your answer

If not go to answer one

9

Thanks @JoelA. Turning off secure boot fixed the problem.

Also thanks to @nevj and @callpaul.eu for your input.

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10

We should all read @JoelA 's reply… No 4

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