Use fallback mechanism in GRUB to automatically recover unbootable system

[bachp]

Issue description

It would be nice if a machine broken configuration would automatically recover into an older generation.
I found that GRUB is supporting fallback which could be used to achieve this.

The machine would try to boot and if the boot fails for some reason it grub would start the previous generation. Other boot loaders probably have similar functionality.

This is especially useful on machines where you don't have access during the boot. For example on AWS I was unable to rollback after a miss configuration because the system couldn't mount the rootfs. A fallback mechanism like would have saved me 😉

[mmahut]

Are there any updates on this issue, please?

[bachp]

I havent' been working on this. But still think it would be nice to be able to use NixOS in a way similar to (Fedora) CoreOS.

[stale]

Thank you for your contributions.

This has been automatically marked as stale because it has had no activity for 180 days.

If this is still important to you, we ask that you leave a comment below. Your comment can be as simple as "still important to me". This lets people see that at least one person still cares about this. Someone will have to do this at most twice a year if there is no other activity.

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[bachp]

This is still relevant

[theduke]

I just ran into a situation where a wrong configuration broke the boot process.

A fallback mechanism would be amazing!

[stale]

I marked this as stale due to inactivity. → More info

[ccie18643]

This is still relevant.

[n8henrie]

Somehow I end up with a non-bootable system semi-frequently (often messing with hardware or kernel options on my several nixos Raspberry Pis). This would be really nice (my Pi4 uses grub, so if grub is required it may still be possible).

EDIT: Currently dealing with this with a remote headless Pi and nixos-rebuild switched without trouble but seems lost after I attempted to reboot. Going to be a few weeks before I can travel to the device and manually revert the boot option.

[dscottboggs]

Just want to leave a note here, this is from K900 in the Matrix chat:

The way this will likely happen is via systemd-boot and automatic boot assessment
We don't support it yet
But we will eventually probably

So for anyone else interested in this, Grub is the wrong place to look.

It also appears that some progress has been made already on this in #84204