Grub menu access

[Don]

I am beginning to suspect that my box (and me, for that matter) may have a memory problem. But when I restart and press <ESC>, I get the grub menu but without the memtest program. All it gives me is Kubuntu and Kubuntu (Advanced options), the latter of which merely allows me to boot to a previous kernel. I'm sure I'm missing something simple.
Thanks.

[Don]

I think I found the answer. I'm installing memtester. After it runs, I'll come back and either mark the post solved or myself as hopeless.

[jlittle]

The free memtest86+ utility that grub used to give an entry for is BIOS only. You can run it by booting a USB that has it in BIOS mode. You can get one from memtest86.com, but they try really hard to divert you to the paid version. I've always used "systemrescue" (formerly known as "systemrescuecd"), though I haven't for a long time.

Memtester runs in "userspace" on top of Linux, so it can't do write tests to memory the OS is using, and maybe some other places.

[claydoh]

As jlittle mentioned memtest only works in older BIOS firmware systems, not the current EFI firmware ones. Well, the open source version doesn't
There is a free-as-in-price version that does work on EFI systems, so this is an option if you need/want an 'offline' memory tester. But. yeah, that website sure feels like one of those dodgy freeware sites.

Some system firmwares allow you to boot using an emulated "Legacy" BIOS, CSM, or some other fancy name, which is one option to get memtest running from the live USB. It can be more work than it is worth, depending on your system's options, but it may be useful since a *buntu iso can boot to either BIOS or UEFI firmware, and iirc memtest should appear in grub when booting it using the Legacy/BIOS/CSM option.

[Don]

Looking in /boot/grub, I see that memtest86+ is there (3 files actually, all dated 2/6/22). I also saw a site that advised just editing the grub.cfg file to include memtest. But since the second line of grub.cfg says (in all caps) "Do not Edit This File," I can take the hint. So how do I edit the grub menu? I see Snowhog's post from 2/19/22 about changing the Timeout setting, but he was talking about a different problem, and I don't see anything in there about the menu.

I also saw online a reference to a beta of memtest86 said to work with a UEFI system. Anyone know anything about that?

[claydoh]

See my link above
The open-source/free memtest is explicitly BIOS-only, so assuming your system is UEFI (and the vast majority of systems are), you can't run memtest86 unless your computer can be set to boot in a legacy BIOS mode. Not all can, but you have to poke around in your firmware (aka bios) settings.
It might be worth poking around there anyway, your firmware might have a tool like this built-in.

You can download a freeware/proprietary version that you can use on UEFI. It burns to a USB just like a Linux ISO image.

[jlittle]

If a computer has done a UEFI boot, it cannot run memtest86+, so when grub generates grub.cfg, it leaves it out. There's various ways to add it back, but there's no point, it cannot work in UEFI mode. Boot a USB in BIOS mode instead. You could buy the "pro" version that supports UEFI, but it wants you to install it to USB anyway.