Some question about nix-channel git commit version and packages

varvir · April 13, 2019, 3:03am

Is there any benefit using nix-channel than git clone [nixpkgs-unstable github repository](https://github.com/NixOS/nixpkgs-channels)?
→ well, i think if cloning, i can’t use cache.nixos.org… and can’t find nix expression like <nixpkgs>… and anything else?
when i nix-env -u <package>, for instance, openjdk8u is upgraded to openjdk11 not latest cache’s openjdk8u. how can i upgrade package to latest cache’s pre-built binary?

acowley · April 15, 2019, 2:33pm

If you are using NixOS, nix channels are, I think, the driver of interactions like this,

$ lsof
The program ‘lsof’ is currently not installed. It is provided by
several packages. You can install it by typing one of the following:
  nix-env -iA nixos.busybox
  nix-env -iA nixos.lsof

That is, a missing executable is tied to a package name (which I typically pull in with nix-shell, rather than nix-env). I find this quite handy, so even though my NIX_PATH points to a normal git clone, I still have a channel set up just for this feature.

roni · May 11, 2019, 4:20pm

This is amazing! But it seems to only work in bash by default. If I prefer to use zsh as my shell, do you know how I can enable this feature there?

lilyball · May 11, 2019, 10:10pm

I just tested on my NixOS machine and I don’t get this behavior even in bash.

> bash -l
$ lsof
lsof: command not found

$

Do I have to do something to enable this?

roni · May 11, 2019, 10:50pm

Good question, I hope someone can weigh in. As far as I can remember, I didn’t do anything to enable that feature, but my NixOS system was installed a long time ago…

ryantm · May 11, 2019, 11:03pm

github.com

NixOS/nixpkgs/blob/c2570ef907129c89e7482770ad9b0d044452574b/nixos/modules/programs/command-not-found/command-not-found.nix

# This module provides suggestions of packages to install if the user
# tries to run a missing command in Bash.  This is implemented using a
# SQLite database that maps program names to Nix package names (e.g.,
# "pdflatex" is mapped to "tetex").

{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.programs.command-not-found;
  commandNotFound = pkgs.substituteAll {
    name = "command-not-found";
    dir = "bin";
    src = ./command-not-found.pl;
    isExecutable = true;
    inherit (pkgs) perl;
    inherit (cfg) dbPath;
    perlFlags = concatStrings (map (path: "-I ${path}/${pkgs.perl.libPrefix} ")
      [ pkgs.perlPackages.DBI pkgs.perlPackages.DBDSQLite pkgs.perlPackages.StringShellQuote ]);

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Should be on by default.

Ryan

roni · May 11, 2019, 11:31pm

Ah, I do have that enable flag set to true, which explains why it works in bash. Any idea why it may not be working for me in zsh?

Thanks!

matthewbauer · May 12, 2019, 1:54am

This might happen if you’re on the nixpkgs channel instead of the nixos one. Check if this file exists:

/nix/var/nix/profiles/per-user/root/channels/nixos/programs.sqlite

lilyball · May 12, 2019, 4:06am

Looks like it’s on for me, it’s just that the database doesn’t contain lsof. If I try e.g. gifasm then it works. Pretty weird that my /nix/var/nix/profiles/per-user/root/channels/nixos/programs.sqlite doesn’t list lsof.

matthewbauer · May 12, 2019, 6:50pm

You can also use nix-index which gives you a little more control over how the db is generated:

$ nix-env -iA nixpkgs.nix-index
$ nix-index

then adding this to your profile:

source $HOME/.nix-profile/etc/profile.d/command-not-found.sh

matthewbauer · May 12, 2019, 6:55pm

You can also do some neat things with the programs.sqlite table. For instance, get all of the 3 letter commands in Nixpkgs:

nix run nixpkgs.sqlite -c sqlite3 /nix/var/nix/profiles/per-user/root/channels/nixos/programs.sqlite 'select * from programs where length(name) = 3 and system = "x86_64-linux";'

roni · May 19, 2019, 10:58pm

BTW, I figured out how to get this working in zsh. It’s just a matter of invoking command-not-found when the shell detects that a command failed, which is done by defining the command_not_found_handler function in zsh:

function command_not_found_handler () {
    command-not-found "$1"
}

JohnAZoidberg · May 20, 2019, 12:41pm

For me it works in fish, too.
And you don’t even need a channel.

I have nixpkgs pinned for my system and make command-not-found work with this configuration: programs.command-not-found.dbPath = "${pinnedNixpkgs.src}/programs.sqlite";.

Note that you can’t use the git tree, you have to use the tarball from https://releases.nixos.org/nixos/unstable/${channelRelease}/nixexprs.tar.xz