List and delete NixOS generations

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1

Hi everybody,

This seems like an obvious questions but I can’t find in manual / on discourse how to list all NixOS generations on my laptop and delete some.

I know about nix store gc but I’d like to for example delete generations from yesterday when I was experimenting but keep a generation from the day before.

I found some mention of nix-env that can do that but I’d prefer to use nix (the new version) if possible.

Thank you.

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2

Go to /nix/var/nix/profiles/ and remove symlinks for generations you want to delete, then nix store gc.

Indeed I didn’t see an obvious place where this is documented - either I didn’t look in the right place yet or that might be something that’s worth improving :slight_smile:

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List generations: nix profile history --profile /nix/var/nix/profiles/system
Delete generations: sudo nix profile wipe-history --profile /nix/var/nix/profiles/system --older-than 14d.
Manuals: man nix3-profile-history and man nix3-profle-wipe-history.

15 Likes
4

Thank you very much both! I’ve just rebuilt twice in a row and nix profile history is showing only one new number - not two. So it’s working as I hoped it will.

Is it possible to see if I’m on the latest generation? For example if I run nixos-rebuild boot --flake ... I shouldn’t be and if I run nixos-rebuild switch --flake ... I should be.

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You could check if /run/current-system/ and /run/booted-system/ point to the same system as /nix/var/nix/profiles/system

1 Like
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Maybe something like this:

diff <(ls -l /run/current-system/ | sort) <(ls -l /run/booted-system/ | sort)
7

Hi folks,

Could you please confirm that this is supported / safe method? Asking since this is not a CLI command and I worry that I that brake something by messing with symlinks.

And I don’t want to use sudo nix profile wipe-history --profile /nix/var/nix/profile/system --older-than 14d since I want to keep a few older generations.

Thank you.

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Deleting symlinks from /nix/var/nix/profiles/ is mostly safe. It might leave you with some broken entries in Grub, but those should be cleaned up with the next nixos-rebuild {boot|switch}.

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Thank you very much!