Declarative Package Management¶
With declarative package management, you specify which packages you want on
your system by setting the option
environment.systemPackages. For instance, adding the
following line to configuration.nix enables the Mozilla
Thunderbird email application:
environment.systemPackages = [ pkgs.thunderbird ];
The effect of this specification is that the Thunderbird package from Nixpkgs will be built or downloaded as part of the system when you run nixos-rebuild switch.
Note
Some packages require additional global configuration such as D-Bus or systemd service registration so adding them to environment.systemPackages might not be sufficient. You are advised to check the list of options whether a NixOS module for the package does not exist.
You can get a list of the available packages as follows:
$ nix-env -qaP '\*' --description
nixos.firefox firefox-23.0 Mozilla Firefox - the browser, reloaded*...*
The first column in the output is the attribute name,
such as nixos.thunderbird.
Note: the nixos prefix tells us that we want to get the
package from the nixos channel and works only in CLI tools.
In declarative configuration use pkgs prefix (variable).
To “uninstall” a package, simply remove it from environment.systemPackages and run nixos-rebuild switch.