Update Nix to Unstable

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Nix has an option to upgrade to stable
upgrade-nix upgrade Nix to the latest stable version

Is there a way for me to upgrade past that?

There is a bug here that was fixed 2 weeks ago, but even on the latest stable the bug still exists so I’d like to upgrade to so I can use the fix.

Edit: Jump to answer summary

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generally this is done through channels.

You’ll want to set your nixpkgs channel to follow the release you want to “upgrade to”. Then you need to use “re-run” the command which consumes that channel

follow new channel:

nix-channel --add https://channels.nixos.org/nixos-20.09 nixos

“fetch” the channel and related package set

nix-channel --update

then run the command that “applies” a channel

nix-env -u '*'
home-manager switch
nix-shell -p ...

For upgrading your system, you’ll just want to run it as sudo

sudo nix-channel --add https://channels.nixos.org/nixos-20.09 nixos

then

sudo nixos-rebuild switch

EDIT: forgot update command

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@jonringer Thanks for the quick response! Sadly I’m not on nixos (the bug itself is a mac-specific)

I added the channel with
nix-channel --add https://channels.nixos.org/nixpkgs-unstable/ unstable

nix-env -u '*' is the only command that worked for me (I don’t have home-manager either).
I’m not sure what the ... should be for nix-shell command.

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nix-shell just drops you into a shell with certain things present

https://www.youtube.com/watch?v=k7NKBfeYXCk a video on it’s usage

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Thanks for the link! I use nix-shell pretty often, I just wasn’t sure why nix-shell -p would be needed for applying the update.

Sadly It looks like the change wasn’t applied, nix --version is still 2.3.7, and the bug still exists.

Edit: @jonringer oh that’s your video! Haha I actually watched it when I was trying to learn nix-shell, thanks for making it!

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Do you perhaps still have other channels active which might cause the issue?

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$ nix-channel --list
nixos https://channels.nixos.org/nixos-20.09
nixpkgs https://channels.nixos.org/nixpkgs-unstable
unstable https://channels.nixos.org/nixpkgs-unstable

After listing I went ahead and removed unstable and nixos since I was getting this error:

warning: name collision in input Nix expressions, skipping '/Users/jeffhykin/.nix-defexpr/channels_root/nixpkgs'

Removing them, then running nix-channel --update followed again with nix-env -u '*' seems to be doing a whole lot of something (installing), so I’ll add a post once its finished

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Oh yea, I forgot to mention, after you’re tracking the channel, you need to do nix-channel --update to pull down the remote information.

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I’m just now realizing nix-env -u '*' is updating every individual package. I was about to say that wasn’t what I wanted to do, since the bug causes nix-env -qa --json to fail and I thought nix-env itself needed to be updated.

But the bug is gone now! So there must be something interestingly recursive about nix-env I don’t understand.

As a slight downside, I’m now getting the following warning with every command, even though I’m only subscribed to one channel now

warning: name collision in input Nix expressions, skipping '/Users/jeffhykin/.nix-defexpr/channels_root/nixpkgs'

Looks like it has something to do with this,

/Users/jeffhykin/.nix-defexpr/channels_root/nixpkgs@ -> /nix/store/kkym0q1g9cy7hxxdng2ivwlyv530mgqk-nixpkgs-20.09pre234801.1facbd61b17/nixpkgs

Probably from when I added the nixos channel. I’m not sure the best way to delete/remove it

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Answer (summary)

If you’re not running NixOS, then

  1. Give your nix-env access to the latest by running
    sudo nix-channel --update
  2. Update all of your packages (which will probably take awhile)
    nix-env -u '*'

If you are running NixOS

  1. nix-channel --add https://channels.nixos.org/nixos-20.09 nixos
  2. nix-env -u '*'
  3. (if you have home-manager) home-manager switch
  4. (if you want to upgrade your system)
sudo nix-channel --add https://channels.nixos.org/nixos-20.09 nixos
sudo nixos-rebuild switch
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Just to close the circle, the fix for the nix-env -qa --json bug on Darwin doesn’t involve the nix executable at all. Rather, it’s a fix within the nixpkgs collection of Nix expressions.

So just updating nixpkgs to a recent enough version is all you need to get the fix, as you discovered.

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Although this is a bit off topic, if I use the -f option for an older commit (example below) will I basically be re-introducing the bug? (will the nix-env be using the -f packages, or only looking/searching them)

nix-env -qa --json -f https://github.com/NixOS/nixpkgs-channels/archive/8414d8386b9a6b855b291fb3f01a4e3b04c08bbb.tar.gz > ~/testJson.json
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I made the mistake of adding the unstable channel to my user channels. Running sudo nix-channel --list revealed that the system channel was still on 21.11 and updating that fixed the issue.

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Btw, I know this is old but it’s one of the first results on $SEARCH_ENGINE.