supporting multiple tries per partition (boot counter) in GRUB

[davidhuwyler]

I was not able to find an example of a GRUB configration to allow more than one try per rauc slot.
Maybe with "test" and "eval" or something?
Or is only one try per slot possible with GRUB?

[jluebbe]

If I remember correctly, the main issue was decrementing the TRY counters. If that's possible in new grub versions, we'd be happy to take a PR implementing that (and adding a second example script to contrib).

[mbessler]

I'm using the following patch for grub that implements a increment/decrement command:
0253-Reimplement-boot_counter.patch from https://src.fedoraproject.org/rpms/grub2/c/db4a99687c8306760702abda9c01a2e74d19a3f3
Direct link: https://src.fedoraproject.org/rpms/grub2/blob/db4a99687c8306760702abda9c01a2e74d19a3f3/f/0253-Reimplement-boot_counter.patch

I also have a patch for rauc that creates a boot loader type "grubalt" to work with this feature. The grub bootscript is basically a port of the rauc u-boot boot selection script.

If there is any interest, I can share both.

[davidhuwyler]

thanks mbessler, very interesting!
I'll try the patch if it works for me.

Ive got a double for loop working now in the grub bootscript to implement a 3 try a b system.
Not very pretty but functional...

[mbessler]

Before I found this patch, I had used some "not very pretty" code to increment/decrement using an if/then/else construct that handled numbers from around 0-10. However should the value be something outside that range, it could not handle it well.
Having the proper increment and decrement functions really helps.

[jluebbe]

I'm using the following patch for grub that implements a increment/decrement command: 0253-Reimplement-boot_counter.patch from https://src.fedoraproject.org/rpms/grub2/c/db4a99687c8306760702abda9c01a2e74d19a3f3 Direct link: https://src.fedoraproject.org/rpms/grub2/blob/db4a99687c8306760702abda9c01a2e74d19a3f3/f/0253-Reimplement-boot_counter.patch

@mbessler Do you know it they plan to upstream this change? I've not found it in https://git.savannah.gnu.org/cgit/grub.git/log/ so far.

I also have a patch for rauc that creates a boot loader type "grubalt" to work with this feature. The grub bootscript is basically a port of the rauc u-boot boot selection script.

If there is any interest, I can share both.

I'd be interested! We could at least take a look if it could be integrated into RAUC without too much overhead. As long as a patched GRUB is needed, I'd like to avoid unnecessary extra code.

[jluebbe]

A related discussion can be found at https://pagure.io/fedora-iot/issue/12.

[mbessler]

@jluebbe no idea, I don't run or follow Fedora/RH, just found the patch useful. It would seem that the increment/decrement would not be a controversial change, but I have not looked into Grub upstream (other than checking for the existence of the feature).

Grubalt bootchooser pull request opened: #1275