ppc64el Trixie Alpha 1 /boot may be ext2 not ext4

Hi Cyril,

the installer components that implement those choices.

thanks for pointing me on this.
I have just pushed a fix for this, reverting back to ext2:
https://salsa.debian.org/installer-team/partman-auto/-/commit/a87cccbe0198b4dea2cc46a39d5f5b99501aa095

Regards
Holger

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Pascal Hambourg

2025-01-12 13:20:02 UTC

Hello,

the installer components that implement those choices.

The move from ext2 to ext4 for /boot was in response to bug #985463
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=985463> after it was
considered that bootloaders such as GRUB and U-Boot currently used with
Debian supported ext4.

Inndeed it is unfortunate that a modern boot loader like Petitboot does
not support ext4. It is even unexpected from a boot loader based on a
Linux kernel, as mentioned in
<https://open-power.github.io/petitboot/overview.html>.

Post by Holger Wansing
thanks for pointing me on this.
https://salsa.debian.org/installer-team/partman-auto/-/commit/a87cccbe0198b4dea2cc46a39d5f5b99501aa095

Partitioning recipes for ppc64el create a separate /boot partition only
when using LVM (and this was never changed). When using plain
partitions, /boot is on the ext4 root partition so the above fix will
have no effect.

According to
<https://github.com/open-power/petitboot/blob/master/README.md> and
<https://open-power.github.io/petitboot/platforms.html>, Petitboot is
also available for arm64 platforms. Partitioning recipes for arm64 also
use ext4 for /boot, so it would not work either.

Holger Wansing

2025-01-12 14:10:02 UTC

Hi,

Hello,

the installer components that implement those choices.

The move from ext2 to ext4 for /boot was in response to bug #985463
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=985463> after it was
considered that bootloaders such as GRUB and U-Boot currently used with
Debian supported ext4.
Inndeed it is unfortunate that a modern boot loader like Petitboot does
not support ext4. It is even unexpected from a boot loader based on a
Linux kernel, as mentioned in
<https://open-power.github.io/petitboot/overview.html>.

Post by Holger Wansing
thanks for pointing me on this.
https://salsa.debian.org/installer-team/partman-auto/-/commit/a87cccbe0198b4dea2cc46a39d5f5b99501aa095

The report was for guided partitioning with encrypted LVM.
So I assumed the above would fit.
Am I missing something?

According to
<https://github.com/open-power/petitboot/blob/master/README.md> and
<https://open-power.github.io/petitboot/platforms.html>, Petitboot is
also available for arm64 platforms. Partitioning recipes for arm64 also
use ext4 for /boot, so it would not work either.

Hmm, is it widely used on arm64, or only a cornercase?
Is it worth to change the default on arm64 just for petitboot?

Holger

--
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Pascal Hambourg

2025-01-12 15:20:01 UTC

the installer components that implement those choices.

The move from ext2 to ext4 for /boot was in response to bug #985463
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=985463> after it was
considered that bootloaders such as GRUB and U-Boot currently used with
Debian supported ext4.
Inndeed it is unfortunate that a modern boot loader like Petitboot does
not support ext4. It is even unexpected from a boot loader based on a
Linux kernel, as mentioned in
<https://open-power.github.io/petitboot/overview.html>.

Post by Holger Wansing
thanks for pointing me on this.
https://salsa.debian.org/installer-team/partman-auto/-/commit/a87cccbe0198b4dea2cc46a39d5f5b99501aa095

The report was for guided partitioning with encrypted LVM.
So I assumed the above would fit.
Am I missing something?

No, I just wanted to make sure everyone is aware that the revert fixes
only this specific use case (guided partitioning using LVM with or
without encryption). The issue already existed and remains when using
guided partitioniong without LVM (ext4 root, no separate /boot).

Post by Pascal Hambourg
According to
<https://github.com/open-power/petitboot/blob/master/README.md> and
<https://open-power.github.io/petitboot/platforms.html>, Petitboot is
also available for arm64 platforms. Partitioning recipes for arm64 also
use ext4 for /boot, so it would not work either.

Hmm, is it widely used on arm64, or only a cornercase?
Is it worth to change the default on arm64 just for petitboot?

One could ask the same about ppc64el. Is Petitboot provided by IBM as
part of this platform firmware ? The recipes for ppc64el create a PReP
partition which, as far as I know, is intended for OpenFirmware + GRUB.

I have no clue about Petitboot on arm64, I didn't know anything about
Petitboot before today. A quick web search shows that Petitboot is used
on arm64-based Odroid boards. An article [1] (in french, sorry) suggests
that it supports ext4, so I wonder why it does not on the OP's machine.

[1]
<https://linuxfr.org/users/pied/journaux/petitboot-sur-arm-le-bon-le-bad-et-le-ugly>

Holger Wansing

2025-01-12 15:50:01 UTC

Hi,

the installer components that implement those choices.

The move from ext2 to ext4 for /boot was in response to bug #985463
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=985463> after it was
considered that bootloaders such as GRUB and U-Boot currently used with
Debian supported ext4.
Inndeed it is unfortunate that a modern boot loader like Petitboot does
not support ext4. It is even unexpected from a boot loader based on a
Linux kernel, as mentioned in
<https://open-power.github.io/petitboot/overview.html>.

Post by Holger Wansing
thanks for pointing me on this.
https://salsa.debian.org/installer-team/partman-auto/-/commit/a87cccbe0198b4dea2cc46a39d5f5b99501aa095

The report was for guided partitioning with encrypted LVM.
So I assumed the above would fit.
Am I missing something?

Ok, so that's fine.
With this fix in place, there is at least the LVM partitioning scheme
(with or without encryption), which works out of the box with default
choice.
And assuming we got no complains before about this situation on this machine,
I guess it's fine this way.

Hmm, is it widely used on arm64, or only a cornercase?
Is it worth to change the default on arm64 just for petitboot?

One could ask the same about ppc64el. Is Petitboot provided by IBM as
part of this platform firmware ? The recipes for ppc64el create a PReP
partition which, as far as I know, is intended for OpenFirmware + GRUB.
I have no clue about Petitboot on arm64, I didn't know anything about
Petitboot before today. A quick web search shows that Petitboot is used
on arm64-based Odroid boards. An article [1] (in french, sorry) suggests
that it supports ext4, so I wonder why it does not on the OP's machine.

Maybe the OP has some information on this...

Holger

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Pascal Hambourg

2025-01-12 18:20:01 UTC

Post by Pascal Hambourg
I just wanted to make sure everyone is aware that the revert fixes
only this specific use case (guided partitioning using LVM with or
without encryption). The issue already existed and remains when using
guided partitioniong without LVM (ext4 root, no separate /boot).

There is too much inconsistency here for me to say it is fine.

On one hand, the recipes for ppc64el create an optional ext2 /boot
partition only with LVM, which means that booting with Petitboot will
fail if the user chooses guided partitioning without LVM.

On the other hand, the recipes for arm64 uselessly create a mandatory
ext4 /boot partition even without LVM.

In between, the recipes for amd64 create an optional ext4 /boot
partition only with LVM and the default recipes create a mandatory ext2
/boot partition in all cases.

Either a common boot loader for a given architecture does not support
/boot on ext4 and then the recipes for this architecture should create a
mandatory ext2 /boot partition in all cases (like default recipes), or
all common boot loaders are known to support /boot on ext4 and then the
recipes should create an optional ext4 /boot partition only with LVM
(like recipes for amd64).

Holger Wansing

2025-01-12 18:50:01 UTC

Hi again,

There is too much inconsistency here for me to say it is fine.

"Is fine" was rather meant as "ok, I understand what you meant".

Post by Pascal Hambourg
On one hand, the recipes for ppc64el create an optional ext2 /boot partition only with LVM, which means that booting with Petitboot will fail if the user chooses guided partitioning without LVM.
On the other hand, the recipes for arm64 uselessly create a mandatory ext4 /boot partition even without LVM.
In between, the recipes for amd64 create an optional ext4 /boot partition only with LVM and the default recipes create a mandatory ext2 /boot partition in all cases.
Either a common boot loader for a given architecture does not support /boot on ext4 and then the recipes for this architecture should create a mandatory ext2 /boot partition in all cases (like default recipes), or all common boot loaders are known to support /boot on ext4 and then the recipes should create an optional ext4 /boot partition only with LVM (like recipes for amd64).

What you describe would be the perfect world.
But what we have here leads to a trade-off anyway.
We cannot do it perfectly right for all cases.

Holger

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Pascal Hambourg

2025-01-12 22:50:01 UTC

There is too much inconsistency here for me to say it is fine.

"Is fine" was rather meant as "ok, I understand what you meant".

Ah, I read it as "the risk of boot failure when using guided
partitioning without LVM is acceptable while nobody complains".

What you describe would be the perfect world.
But what we have here leads to a trade-off anyway.
We cannot do it perfectly right for all cases.

In a perfect world, all boot loaders would support /boot on ext4 and we
would not have to make trade-offs. Indeed we must make a trade-off
between robustness (ext4 vs ext2), convenience (/boot in root filesystem
vs small separate /boot) and compatibility with boot loaders. And I
believe we can do it right at least for use cases we know about. You
addressed the case of guided partitioning without LVM on ppc64el, why
not do the same for guided partitioning without LVM ? Do you think that
the robustness or convenience gain of not having a separate ext2 /boot
partition is worth the loss of compatibility with Petitboot ?

Holger Wansing

2025-01-13 06:50:01 UTC

Hi,

In a perfect world, all boot loaders would support /boot on ext4 and we would not have to make trade-offs. Indeed we must make a trade-off between robustness (ext4 vs ext2), convenience (/boot in root filesystem vs small separate /boot) and compatibility with boot loaders. And I believe we can do it right at least for use cases we know about. You addressed the case of guided partitioning without LVM on ppc64el, why not do the same for guided partitioning without LVM ? Do you think that the robustness or convenience gain of not having a separate ext2 /boot partition is worth the loss of compatibility with Petitboot ?

I cannot judge on this, because it depends on, how much Petitboot
is used on that arch.
If it's only some few percent, you would force much other people to
a ext2 /boot without a reason.
And the same for arm64, if we roll back to ext2 there too.

I had hoped that the OP would give some statistics about this...

Holger

--
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Pascal Hambourg

2025-01-13 08:40:01 UTC

Post by Pascal Hambourg
Indeed we must make a trade-off
between robustness (ext4 vs ext2), convenience (/boot in root filesystem
vs small separate /boot) and compatibility with boot loaders. And I
believe we can do it right at least for use cases we know about. You
addressed the case of guided partitioning without LVM on ppc64el, why
not do the same for guided partitioning without LVM ? Do you think that
the robustness or convenience gain of not having a separate ext2 /boot
partition is worth the loss of compatibility with Petitboot ?

I cannot judge on this, because it depends on, how much Petitboot
is used on that arch.
If it's only some few percent, you would force much other people to
a ext2 /boot without a reason.

I agree. Petitboot is mentioned on IBM's website [1] so I suspect it is
rather standard on IBM POWER machines.

[1]
<https://www.ibm.com/docs/en/linux-on-systems?topic=systems-petitboot-bootloader>

Post by Holger Wansing
And the same for arm64, if we roll back to ext2 there too.

AFAIK the only implementation of Petitboot on arm64 (Odroid) supports
ext4 so there is no need to rollback to ext2. I did not mean to roll
back to ext2 but to create a separate /boot partition only with LVM, as
I do not see the benefit of a separate ext4 /boot partition without LVM.

Post by Holger Wansing
I had hoped that the OP would give some statistics about this...

So do I...

Diederik de Haas

2025-01-13 13:40:01 UTC

I cannot judge on this, because it depends on, how much Petitboot
is used on that arch.
If it's only some few percent, you would force much other people to
a ext2 /boot without a reason.

I agree. Petitboot is mentioned on IBM's website [1] so I suspect it is
rather standard on IBM POWER machines.
[1]
<https://www.ibm.com/docs/en/linux-on-systems?topic=systems-petitboot-bootloader>

Post by Holger Wansing
And the same for arm64, if we roll back to ext2 there too.

Post by Holger Wansing
I had hoped that the OP would give some statistics about this...

So do I...

FWIW, I hadn't heard about Petitboot before this bug either, so I looked
on their Github repo and found "and ARM64 with ACPI" ... and I think the
"with ACPI" is significant.
So going back to ext2 on arm64 just for Petitboot users seems a bit
heavy handed to me (but I may not fully understand it all).

My 0.02

Pascal Hambourg

2025-01-13 20:20:02 UTC

Post by Diederik de Haas

Post by Pascal Hambourg
AFAIK the only implementation of Petitboot on arm64 (Odroid) supports
ext4 so there is no need to rollback to ext2. I did not mean to roll
back to ext2 but to create a separate /boot partition only with LVM, as
I do not see the benefit of a separate ext4 /boot partition without LVM.

Do I need to repeat that I did no suggest to revert the /boot partition
to ext2 on arm64 ? I found other evidence that Petitboot supports ext4:

<https://discourse.nixos.org/t/newbie-installs-nixos-on-an-arm-sbc-or-how-patience-is-a-virtue/35020>
Odroid ARM64
"Additionally when making a new installation, Petitboot supports ext2,
ext3 and ext4 and a couple other filesystems like vfat and iso9660, so
/boot should be on one of those."

<https://forum.odroid.com/viewtopic.php?p=251632>
Odroid ARM64
"OS in the memory card can boot from Petitboot if the type of the root
file system is ext2/3/4."

This one is even more interesting:

<https://www.reddit.com/r/ps3homebrew/comments/18mzyvu/petitboot_ext4/?rdt=46856>
PS3 POWER
"I noticed that petitboot can boot from ext4, but only if it was created
inside petitboot itself. For some reason if I create it using Gentoo,
petitboot is not able to mount it. What could be the difference that
makes it unsupported?"

Maybe some Petiboot instances use older kernels which do not support new
ext4 features enabled by default in more recent e2fsprogs ?

Diederik de Haas

2025-01-13 20:30:01 UTC

Post by Diederik de Haas

Do I need to repeat that I did no suggest to revert the /boot partition

Not AFAIC. My post was basically a +1 on yours + some possible extra
arguments to support using ext4 on arm64 and not reverting to ext2.
And FWIW, I also found 'hints' that ext4 not working was to be
considered an anomaly itself.

Holger Wansing

2025-01-14 21:50:01 UTC

Hi,

Post by Pascal Hambourg
In a perfect world, all boot loaders would support /boot on ext4 and we
would not have to make trade-offs. Indeed we must make a trade-off
between robustness (ext4 vs ext2), convenience (/boot in root filesystem
vs small separate /boot) and compatibility with boot loaders. And I
believe we can do it right at least for use cases we know about. You
addressed the case of guided partitioning without LVM on ppc64el, why

without -> with ^^^

Post by Pascal Hambourg
not do the same for guided partitioning without LVM ? Do you think that
the robustness or convenience gain of not having a separate ext2 /boot
partition is worth the loss of compatibility with Petitboot ?

Ok, so I have now changed that, to create a separate ext2 /boot partition
for the non-lvm case as well.

Holger

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John Paul Adrian Glaubitz

2025-01-13 08:50:01 UTC

Hello,