Public bug reported:
Description: Ubuntu 20.04.4 LTS
Release: 20.04
grub-pc 2.04-1ubuntu26.15
Booting Ubuntu 20.04.4 from a 4TiB partition partition on a 4TiB GPT disk.
I have grub bootblocks installed in a bios-grub partition, sectors 34-2047,
bios-grub flag.
The Ubuntu bootable partition is a plain 4TB ext4.
Suddenly, after a routine automatic Ubuntu kernel update, the boot started to
break with message:
"error: attempt to read or write outside of disk (hd0)."
Boot-Repair didn't find nor fix anything.
fscheck found nothing bad.
After a painful search, I realized that part of the new kernel file had been
allocated by the filesystem above the 2TiB limit...
Some more investigation in the Grub documentation suggested that by default,
Grub uses BIOS drivers to load files from the target partition. This is tersely
documented in the Grub 2.06 documentation, in the "nativedisk" command
paragraph.
And the BIOS drivers are limited to 32-bit sector addresses, i.e. 2TiB.
The native Grub drivers don't have this limitation (empirical find, when they
are used, the same kernel file loads - and using them fixes the problem for
good).
So when using native grub drivers (ahci in my case), everything works.
Native drivers can be activated from Grub Rescue using
nativedisk
But a better and longer-lasting solution is to insert them into the bootblocks
by running grub-install with a parameter such as
--disk-module=ahci
(could be ahci, ehci, ATA, ohci or uhci according to harware).
So I solved the problem by re-running a grub-install on that disk with parameter
--disk-module=ahci
The problem with that approach is that any further grub-install without those
parms (like an Ubuntu software update or upgrade might decide to do?) will zap
the native driver from the Grub partition, and break the boot again.
grub-install (and/or update-grub) should never generate a potential broken boot
when it can avoid it:
Couldn't it (shouldn't it) detect when one of the boot partitions in the boot
menu crosses the 2TiB mark, give a warning, and generate a grub-install with
the appropriate --disk-module=MODULE parameter?
4TB SSD disk prices dropping fast (below 350€ these days). This problem
might increasingly show up...
** Affects: grub2 (Ubuntu)
Importance: Undecided
Status: New
** Tags: grub grub-pc
** Description changed:
Description: Ubuntu 20.04.4 LTS
Release: 20.04
+ grub-pc 2.04-1ubuntu26.15
+
Booting Ubuntu 20.04.4 from a 4TiB partition partition on a 4TiB GPT disk.
I have grub bootblocks installed in a bios-grub partition, sectors 34-2047,
bios-grub flag.
The Ubuntu bootable partition is a plain 4TB ext4.
Suddenly, after a routine automatic Ubuntu kernel update, the boot started to
break with message:
"error: attempt to read or write outside of disk (hd0)."
Boot-Repair didn't find nor fix anything.
After a painful search, I realized that part of the new kernel file had been
allocated by the filesystem above the 2TiB limit...
Some more investigation in the Grub documentation suggested that by default,
Grub uses BIOS drivers to load files from the target partition. This is tersely
documented in the Grub 2.06 documentation, in the "nativedisk" command
paragraph.
And the BIOS drivers are limited to 32-bit sector addresses, i.e. 2TiB.
The native Grub drivers don't have this limitation (empirical find, when they
are used, the same kernel file loads!)
So when using native grub drivers (ahci in my case), everything works.
- Native drivers can be activated from Grub Rescue using
- nativedisk
+ Native drivers can be activated from Grub Rescue using
+ nativedisk
But a better a longer-lasting solution is to insert them into the bootblocks
by running grub-install with a parameter such as
--disk-module=ahci
(could be ehci, ATA, ohci or uhci according to harware).
So I solved the problem by re-running a grub-install on that disk with
parameter
--disk-module=ahci
The problem with that approach is that any further grub-install without those
parms (like an Ubuntu software update or upgrade might decide to do?) will zap
the native driver from the Grub partition, and break the boot again.
grub-install (and/or update-grub) should never generate a potential broken
boot when it can avoid it:
Couldn't it (shouldn't it) detect when one of the boot partitions in the boot
menu crosses the 2TiB mark, give a warning, and generate a grub-install with
the appropriate --disk-module=MODULE parameter?
4TB SSD disk prices dropping fast (below 350€ these days). This problem
might increasingly show up...
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https://bugs.launchpad.net/bugs/1970236
Title:
Grub2 bios-install defaults to BIOS disk drivers
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