Using memtest86 with UEFI

[gene heskett]

On Thursday, 14 April 2022 12:17:16 EDT Robert Heller wrote:
> At Thu, 14 Apr 2022 17:57:12 +0200 "Ubuntu user technical support,? not 
for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:
> > On Thu, 14 Apr 2022 at 17:33, gene heskett <gheskett at shentel.net> 
wrote:
> > > That line of users is already quite long, Liam, I am in it too. If
> > > memtest86 is incompatible with UEFI, or vice-versa, that needs to
> > > have
> > > been fixed, 6 years ago?
> > > 
> > > Why has it not been?
> > 
> > If it is a 16-bit binary, that might be why. I know that people have
> > problems with early MacBooks that have 32-bit UEFI firmware but
> > 64-bit
> > processors. No normal 32-bit-only PCs had UEFI, so all Linux distros
> > expect UEFI to be 64-bit and 32-bit machines to not be UEFI. The
> > combination of 2 things that should not be found together apparently
> > makes it hard to install Linux on certain now-old MacBooks.
> > 
> > More info, merely as an example:
> > https://mattgadient.com/linux-dvd-images-and-how-to-for-32-bit-efi-ma
> > cs-late-2006-models/
> > 
> > If 32-bit UEFI is a problem, then a 16-bit UEFI payload is probably
> > next to impossible. :-( And if they made memtestx86+ fully 64-bit it
> > would stop working on older 32-bit and BIOS-only PCs.
> > 
> > Damned if you do, damned if you don't. :-/
> > 
> > > Take care abd stay well, Liam.
> 
> memtest86 appears to a somewhat strange beast:
> 
> sauron% file /boot/memtest86/memtest.bin
> /boot/memtest86/memtest.bin: DOS/MBR boot sector
> sauron% file /boot/memtest86/memtest.img
> /boot/memtest86/memtest.img: DOS/MBR boot sector
> sauron% file /boot/memtest
> /boot/memtest: DOS/MBR boot sector
> sauron% fdisk -l /boot/memtest
> Disk /boot/memtest: 161 KiB, 164864 bytes, 322 sectors
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: dos
> Disk identifier: 0x52c3ebe2
> 
> Device         Boot    Start        End    Sectors  Size Id Type
> /boot/memtest1      12124343 3284782550 3272658208  1.5T 5a unknown
> /boot/memtest2       6778473    6778473          0    0B 4c unknown
> /boot/memtest4             0          0          0    0B  0 Empty
> 

> Partition table entries are not in disk order.

I've seen that too, Robert, and it generally means near future trouble.
And hoping you have backups. You are gonna need them to fix it.
gparted was for a while a step in the right direction, as it could move 
partitions at one time w/o data loss, but that ability seems to have 
disappeared 3 or 4 years ago.

Take care and stay well Robert.

> > You too!
> 
> --
> Robert Heller             -- Cell: 413-658-7953 GV: 978-633-5364
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> 
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Cheers, Gene Heskett.
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis