List-generations and rollback to any configuration

[danbst]

Issue description

I'd like to nixos-rebuild switch --rollback system to an old configuration, but current interface allows rollback only to previous one.

In NixOps, for-example, you can specify the generation number you'd like to rollback to. The generations and their numbers are shown with nixops list-generations

Doing things manually show an error:

# ln -sf /nix/store/5y0ypnyz6mrh95a71qk82kx5cwxfy1dl-nixos-system-nixos-16.09.773.b8ede35 /nix/var/nix/profiles/system
ln: failed to create symbolic link '/nix/var/nix/profiles/system/5y0ypnyz6mrh95a71qk82kx5cwxfy1dl-nixos-system-nixos-16.09.773.b8ede35': Read-only file system

Technical details

• System: nixos-16.09

[danbst]

#24280 is a bit related. Strange part is ln -s works, but ln -sf - doesn't.

[RonnyPfannschmidt]

there is a -T missing so ln will not resolve the target as a folder

[jonas-schievink]

This would still be really nice to have

[JosephLucas]

Yes this would be a nice feature

[thanegill]

You can list system generations with this:

sudo nix-env --list-generations --profile /nix/var/nix/profiles/system

[Atemu]

@thanegill awesome, thank you!

Is it possible to list a bit more information like NixOS channel of the generation and Kernel version like it's shown in the bootloader?

Edit: Found a way.

/nix/var/nix/profiles/system contains links to all the generations, you can just ls -l it and the nix store paths they point to each contain channel and version.

These nix store paths then contain a kernel link which you can also ls -l or readlink to print that generation's kernel's nix store path which contains the kernel version of course.

[stale]

Thank you for your contributions.
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[lboklin]

I'd still like to see a way to switch between existing generations. Last night I had to get back to a generation associated to a different profile and what I had to do was build a new generation of that profile and then rollback over and over until I reached the desired one. That was not a smooth experience.

[miallo]

I would love to be able to revert to absolute generations (e.g. nixos-rebuild switch --rollback=2) or relative (maybe in a git style nixos-rebuild switch --rollback=current~2).

[mixmixmix]

Is there a technical challenge in getting that implemented, anyone knows?

[miallo]

I took a short look into the code and as far as I can see, nixos-rebuild --rollback uses nix-env --rollback, which has a hardcoded relative previous generation. There is also nix-env --switch-generation which could go to an absolute generation instead. So from what I can see, at least going to absolute generations should be relatively straight forward. For a unified interface, rollback to a fixed generation should be done with nixos-rebuild --switch-generation <generation> as well I think

[miallo]

I have just implemented an untested version and I will try it out tomorrow or so. Be carefull if you use it - it was just done by copying the --rollback option and it has been some months since I wrote my last bigger shell script!

[miallo]

Seems to work :)
If you don't want to fiddle with your core system, you could use this for now:

sudo nix-env --switch-generation 12345 -p /nix/var/nix/profiles/system
sudo /nix/var/nix/profiles/system/bin/switch-to-configuration switch

(Replace the 12345 with the generation you want)

[miallo]

I added list-generations action in #105910 as well which has some additional output like Kernel version and NixOS version compared to the solution by @thanegill.
Many ideas come from the script that builds the grub-menu

[stale]

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

[miallo]

Is anyone here in for a review of #105910?

[edrex]

For those looking for a way to do this now:

• Boot into the desired generation via the boot menu
• Run /run/current-system/bin/switch-to-configuration boot (source code)

This sets the current generation as the active one, with the advantage that you've just tested it's bootable.

via: https://www.reddit.com/r/NixOS/comments/ni9u5l/nixos_rollback_questions/

Added to wiki: https://nixos.wiki/wiki/NixOS#Generations

[stale]

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

[Sepero]

Seems to work :) If you don't want to fiddle with your core system, you could use this for now:

sudo nix-env --switch-generation 12345 -p /nix/var/nix/profiles/system
sudo /nix/var/nix/profiles/system/bin/switch-to-configuration switch

(Replace the 12345 with the generation you want)

Also to list generations.

sudo nix-env --list-generations -p /nix/var/nix/profiles/system

Thank you. This fix works with a headless system. Until this is implemented officially, I will have to put these commands in a script.

[tobiasBora]

Also it would be great if nixos-rebuild boot could be set to an old derivation. For some reasons I can't always choose that I startup (not sure why the raspberry pi does not always recognize the keyboard) and it would be great to have.

[Sepero]

Also it would be great if nixos-rebuild boot could be set to an old derivation. For some reasons I can't always choose that I startup (not sure why the raspberry pi does not always recognize the keyboard) and it would be great to have.

Use this to boot to a previous generation. Replace 28 with your generation.

nix-env --switch-generation 28 -p /nix/var/nix/profiles/system

[euonymos]

Use this to boot to a previous generation. Replace 28 with your generation.

nix-env --switch-generation 28 -p /nix/var/nix/profiles/system

Didn't work for me for some reason. It said it did switch, but I still saw a newer version from the last profile. nixos-rebuild switch --rollback did the job.

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/docker-run-and-docker-exec-error/30848/4

[miallo]

The list-generations is now merged into master #250501 🎉
Next step is the specific generation #105910 😄