Proper way to delete the latest system configuration and Grub entry, not the old ones?

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I recently broke my NixOS system (system-4), and rolled back to the previous working version (system-3) using:

/run/current-system/bin/switch-to-configuration boot

That correctly set my Grub default to system-3, but it didn’t delete system-4 from the Grub “All Configurations” menu.

I’d like to completely delete system-4, both from /nix/var/nix/profiles/system and from the Grub “All Configurations” menu. I don’t want to bother debugging it, just want to start over again with system-3 as the current generation system.

The manual only tells how to delete old generations. But what’s the proper way to delete the current system?

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The manual only tells how to delete old generations. But what’s the proper way to delete the current system?

You can delete the various symlinks under /nix/var/nix/profiles and then garbage collect, but why bother? Just fix up the configuration and create a new generation.

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Thanks. I didn’t keep a backup of the known working configuration.nix, so all I have is the broken one. I’m not sure what broke it, so I’m not sure how easy it will be to recreate a new working generation.

I’ve since decided to rebuild my configuration.nix from the default working one, one bit at a time, using the system.copySystemConfiguration setting to keep backups of each build’s configuration.nix.

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general tip: just run git init in your /etc/nixos, don’t have to upload it anywhere, but is kind of helpful.

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Thanks. I didn’t keep a backup of the known working configuration.nix

But the configuration.nix isn’t stored as part of the generation, so even if you were to remove the non-working one, that still wouldn’t get you back to a working state. I cannot strongly enough recommend keeping the configuration in $VCS, use frequent, small commits and tag working configurations.

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with git in /etc/nixos
you are working on it with root rights …

I prefer a git repo anywhere and Symbolic Links to /etc/nixos

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Ah Yeah, I just changed the permissions of /etc/nixos so it is owned by my user; forgot that Part. But now I also use a symlink, just wanted to with the easiest solution.