How to (un-)install & upgrade software in NixOS.
Like any other distro, NixOS has its own package manager, called Nix. Below is a lunar-orbit view of package management in NixOS.
Nix is NixOS's workhorse, so it's a good idea to do some background reading about it. The essentials:
- Introduction. Getting the what and the how.
- Basic Package Management. Using
nix-envto (un-)install, upgrade, and query packages. - Profiles. Or what's going on under the hood. Think of a profile as whole system environment (config + packages) you can switch to.
- Channels. Where packages come from.
If you still have some time to spare, why not learning about
- Nix Expressions. A purely functional language for building and configuring packages. Wow!
Knowing the language comes handy when dealing with NixOS configuration. Also, you'll need to know it if you want to put together your own packages. (Not as difficult as it sounds!)
Packages come from repos called "channels". If you subscribe to a channel, you can install packages from that channel. The NixOS installer subscribes you to the "nixos" (stable) channel of the NixOS release you've installed, as you can see from
$ nix-channel --list | grep nixos
Use nix-env to see what packages are available to install, e.g.
$ nix-env -qaP '.*emacs.*' --description
System-wide packages should normally go in the NixOS system config, e.g.
environment.systemPackages = [ pkgs.emacs ];
As usual, nixos-rebuild switch implements your config, taking care of
the packages you've declared:
- Installation. Any package you've added will be installed.
- Removal. Any package you've removed will be uninstalled.
To upgrade your existing packages and NixOS to the latest available in the channels you've subscribed to:
$ nixos-rebuild switch --upgrade
Keeping packages in your system configuration makes it possible to easily
reinstall the system from scratch with a single nixos-rebuild switch.
For user-specific packages, each user can manage their own set using
nix-env. For example,
$ nix-env -iA nixos.emacs
installs Emacs only in the current user's environment. Installed packages
get recorded in ~/.nixpkgs/config.nix, so you could alternatively use a
configuration-based approach where you edit this file to add and/or remove
packages, then
$ nix-env -i all
to realise your configuration. As a user, you can have as many environments
(Nix profiles) as you like and use nix-env to switch to any of them.
There's a NixOS wiki page you can read to find out more about updating packages and using the configuration-based approach (a.k.a. package collections) outlined above.
So you've taken the whirlwind tour. Now you may want to read the NixOS manual to learn how to fine-tune what gets installed when and how:
- Upgrading NixOS. Keeping your system up-to-date using NixOS channels.
- Package Management. (Un-)Installing, upgrading, and customising packages.
- Cheat sheet. Handy comparison with Debian-like package management.
Also don't forget to do some background reading about Nix: basic package management, profiles, and channels.