Does Grub2 booted live load itself into a cache?(Solved)

[baldronicus]

Hi. I am not sure if this really the correct place to post this topic. I selected this area as things were noticed after using a USB that had been setup using the Fatdog64-811 usb-mbr.img (I might have this name round about as my memory isn't the best). However, I suspect it might be a more generic thing. So, if it is thought that it should go elsewhere, please feel free to move it.

Also apologies for the long-winded description.

I doubt that this will arise very often, but I thought I should ask.

Using F8 during the initial startup, so as to select the boot device, I had booted the USB that I call a multi-boot Fatdog64-811 drive on an ASUS Prime-B450-Plus motherboard, in CSM mode. This was to try out Slacko64-8.2.1. I ran into a problem after the system reached the Quick Setup screen (no keyboard or mouse interaction). Anyway, I thought I would try a CD-RW so that all the menu options would be available. It should be mentioned that this computer is resting on it's side, so that the optical drive is in a vertical orientation rather than horizontal. The first test was just booting the CD-RW (again using F8) as normal, to check that I hadn't messed up copying files. The CD-RW loaded the Slacko menu, ready for selection. As expected, the end result was the same.

Upon rebooting, and, again, selecting the optical drive as the boot device (via F8), the menu that loaded was that from the multi-boot Fatdog64-811 USB drive. I tried again with the same result. I then removed the CD-RW and rebooted again. This time the system fell back to the default boot device Grub2 menu, as normal.

I, kind of, suspect that the CD-RW may have moved and, although it was still identifiable as a boot device, the Slacko grub.cfg file may not have been readable, so the system fell back to the Fatdog one.

However, how was the Fatdog one available, since, as far as I can recall (unless I had messed up somewhere), it had only been used live? Of course, I can't recall which machine I originally used to copy the image to the USB.

I just seems strange. Is it normal for Grub2 to automatically load itself into some boot area, even though it is not being installed? Would the UEFI BIOS (even though in CSM mode) automatically save various boot configuration files? Although I usually boot in CSM mode the USB drive can boot in either UEFI or CSM, so it could have been booted in UEFI mode at some stage.
Thanks.

[bigpup]

When computers boot.
The UEFI bios activates the hardware and then looks for a boot loader, on one of the drives, to boot and load the operating system.
This boot loader is on the drive, the operating system is on.

The UEFI bios or any bios, when it starts the boot process, looks for and finds, bootable drives.
If you go into the UEFI setup, usually under the boot section.
There will be option to choose the boot device order.
What device to look at first, second, third, etc..... for a boot loader.
The first one is the default boot device.
If that one has no boot loader, it looks at the next one, and so on.
So, the order of drives listed here, is controlling device, to boot from.

Usually the boot device order is setup as:
CD drive
Internal HDD's
USB drive or SD card drive
etc.....
But you can change this to any order.

So no disk in the CD or does not see the boot loader on it.
It goes to the next drive in the list, looking for a boot loader.
When it finds a boot loader.
That one gets used.

When you press F8 key.
You are bringing up a different manual way to select the boot device to use.
You are bypassing, the above auto method device order, in the UEFI setup.
But if you choose a device and the boot loader is not found on it.
It may just go to looking on the next device.
Sometimes, computers just do things, because they can!

[baldronicus]

Hi @bigpup . Thank you for your advice. I think you should send some more laughing faces this way, as it appears that it may not just be computers that will do strange things because they can! Blind as a bat Baldronicus will too (shaking head) !
Whilst trying again, I realised that the disk was being read OK. I wasn't reading the menu properly on the restarts, and was selecting the UEFI entry for the optical drive, rather than the SATA entry. D'oh.
Presumably the UEFI had saved a copy of the grub configuration from the USB for some reason (at some stage) and then was resorting to that when I was making an erroneous selection. Apologies for all the reading and writing.
Thanks again.

[Clarity]

I have a similar computer issue with one of my 64bit PCs. Mine is an HP and I MUST poweroff before ANY reboot attempts. Its the ONLY PC I MUST do this to. All other PCs in the house allow reboots and function-key access as expected.

The BIOS & UEFI over the years are very inconsistent...no matter the manufacturer. AND, most of us have never upgraded the BIOS/UEFI per the manufacturer's releases which corrects many problems. In my case this is true as most of my PCs are discards given to me.

Try power off each time you need to reboot that PC.

[baldronicus]

Hi @bigpup and @Clarity . I think I might have found out how I did it.

Big note to self: don't leave a USB drive plugged in when you are going to access a UEFI BIOS, regardless of whether it is in full UEFI, or CSM mode, unless you are deliberately intending to use it for some set-up mechanism.

Yes, bumbling Baldronicus, Bean, Magoo did it again (another shake of the head) .
Thanks.

[Clarity]

In my case: This ONLY happens on 1 of my PCs. Other models do not exhibit this behavior.

It is important to note, though, what to look for when this problem is seen.

We may need to make a checklist somewhere for others to reference on the many boot problems we, PUP-DOG users, encounter.