is a mechanism that allows you to automatically stay up-to-date with a set of pre-built Nix Expressions. A Nix channel is just a URL that points to a place containing a set of Nix expressions. page 
status
nix-env -qaP | grep emacs warning: name collision in input Nix expressions, skipping '/Users/rgb/.nix-defexpr/channels_root/darwin' suggestion: remove 'darwin' from either the root channels or the user channels warning: name collision in input Nix expressions, skipping '/Users/rgb/.nix-defexpr/channels_root/home-manager' suggestion: remove 'home-manager' from either the root channels or the user channels error: attribute 'definitionsWithLocations' missing at /nix/store/gawrglfj2lqm1ibj2p7xh43dk6a8rzq1-darwin/darwin/modules/nix/nixpkgs.nix:34:17: 33| ) 34| opt.definitionsWithLocations | ^ 35| ) (use '--show-trace' to show detailed location information)
nix-channel --list darwin https://github.com/LnL7/nix-darwin/archive/master.tar.gz home-manager https://github.com/nix-community/home-manager/archive/master.tar.gz
~/.nix-defexpr:
channels -> /nix/var/nix/profiles/per-user/rgb/channels channels_root -> /nix/var/nix/profiles/per-user/root/channels
nix-channel --add https://github.com/LnL7/nix-darwin/archive/master.tar.gz darwin
nix-channel --add https://github.com/nix-community/home-manager/archive/master.tar.gz home-manager
Remove 'darwin' from the user channels
nix-channel --remove darwin
Note: Run `darwin-rebuild switch` as root logged in.
Remove 'home-manager' from the user channels
nix-channel --remove home-manager
nix-env -qaP | grep emacs nixpkgs.emacs emacs-28.1 nixpkgs.emacs28NativeComp emacs-28.1 nixpkgs.emacs-all-the-icons-fonts emacs-all-the-icons-fonts-5.0.0 nixpkgs.emacsMacport emacs-mac-27.2-8.3 nixpkgs.emacs-nox emacs-nox-28.1 nixpkgs.pinentry_emacs pinentry-1.2.0 nixpkgs.pinentry-emacs pinentry-1.2.0 nixpkgs.qemacs qemacs-0.3.3 nixpkgs.vscode-extensions.tuttieee.emacs-mcx vscode-extension-tuttieee-emacs-mcx-0.37.1