Support "nix-collect-garbage -d --keep-generations 2"

[domenkozar]

Would be very useful to be able to keep last X generation when doing garbage collection.

[musteresel]

Has there ever been any work to implement this feature? What parts of nix would one need to touch?

Adding this for reference:

nix-env --list-generations | head -n -3 | while read num date; do echo "$num"; done | xargs nix-env --dry-run --delete-generations

[mogorman]

i actually wrote a pr for that #767

[jackjennings]

This was added in the previously linked PR: #767

[bbigras]

Does nix-collect-garbage has something like --keep-generations?

It seems that the PR added --keep-generations to nix-env. I have no idea how to use it with nix-collect-garbage to clean system stuff.

[alarsyo]

Could this be reopened as it would be really useful in nix-collect-garbage? Currently the only way to delete the k last NixOS generations is to run the following command:

nix-env --delete-generations +k --profile /nix/var/nix/profiles/system

making this usage incompatible with all the nix.gc NixOS module options, which only allow passing flags to nix-collect-garbage.

[OleMussmann]

It could be dangerous for systems that have longer down-times to have their generations scrubbed by time. A buffer of a certain number of generations could prevent that. Please consider re-opening this issue.

[EternityForest]

If this is already solved, could we get some documentation on how to use it?

[zk395]

Would really love to see this kind of feature.

[miku86]

Any news on this?

I have a system that gets updated only once every some months.
Using --delete-older-than is not very practical here, because most config changes are at the same day, so I can either delete all of them or none.

[Pandapip1]

I'd recommend just opening a new issue. It seems unlikely that a maintainer will just stumble across this issue and reopen it.

[Ericson2314]

#9894 should help, and I am sorry to say I am just behind on reviewing that because of other tasks.

[Pandapip1]

It seems unlikely that a maintainer will just stumble across this issue and reopen it.

I stand corrected.