The main command for package management is nix-env. You can use it to install, upgrade, and erase packages, and to query what packages are installed or are available for installation. In Nix, different users can have different “views” on the set of installed applications. That is, there might be lots of applications present on the system (possibly in many different versions), but users can have a specific selection of those active — where “active” just means that it appears in a directory in the user’s PATH. Such a view on the set of installed applications is called a user environment, which is just a directory tree consisting of symlinks to the files of the active applications. Components are installed from a set of Nix expressions that tell Nix how to build those packages, including, if necessary, their dependencies. There is a collection of Nix expressions called the Nix Package collection that contains packages ranging from basic development stuff such as GCC and Glibc, to end-user applications like Mozilla Firefox. (Nix is however not tied to the Nix Package collection; you could write your own Nix expressions based on it, or completely new ones.) You can download the latest version from . Assuming that you have downloaded and unpacked a release of Nix Packages, you can view the set of available packages in the release: $ nix-env -qaf nixpkgs-version '*' ant-blackdown-1.4.2 aterm-2.2 bash-3.0 binutils-2.15 bison-1.875d blackdown-1.4.2 bzip2-1.0.2 ... where nixpkgs-version is where you’ve unpacked the release. The flag -q specifies a query operation; -a means that you want to show the “available” (i.e., installable) packages, as opposed to the installed packages; and -f nixpkgs-version specifies the source of the packages. The argument '*' shows all installable packages. (The quotes are necessary to prevent shell expansion.) You can also select specific packages by name: $ nix-env -qaf nixpkgs-version gcc gcc-3.4.6 gcc-4.0.3 gcc-4.1.1 It is also possible to see the status of available packages, i.e., whether they are installed into the user environment and/or present in the system: $ nix-env -qasf nixpkgs-version '*' ... -PS bash-3.0 --S binutils-2.15 IPS bison-1.875d ... The first character (I) indicates whether the package is installed in your current user environment. The second (P) indicates whether it is present on your system (in which case installing it into your user environment would be a very quick operation). The last one (S) indicates whether there is a so-called substitute for the package, which is Nix’s mechanism for doing binary deployment. It just means that Nix knows that it can fetch a pre-built package from somewhere (typically a network server) instead of building it locally. So now that we have a set of Nix expressions we can build the packages contained in them. This is done using nix-env -i. For instance, $ nix-env -f nixpkgs-version -i subversion will install the package called subversion (which is, of course, the Subversion version management system). When you do this for the first time, Nix will start building Subversion and all its dependencies. This will take quite a while — typically an hour or two on modern machines. Fortunately, there is a faster way (so do a Ctrl-C on that install operation!): you just need to tell Nix that pre-built binaries of all those packages are available somewhere. This is done using the nix-pull command, which must be supplied with a URL containing a manifest describing what binaries are available. This URL should correspond to the Nix Packages release that you’re using. For instance, if you obtained a release from , then you should do: $ nix-pull http://nixos.org/releases/nixpkgs/nixpkgs-0.12pre11712-4lrp7j8x/MANIFEST If you then issue the installation command, it should start downloading binaries from nixos.org, instead of building them from source. This might still take a while since all dependencies must be downloaded, but on a reasonably fast connection such as a DSL line it’s on the order of a few minutes. Naturally, packages can also be uninstalled: $ nix-env -e subversion Upgrading to a new version is just as easy. If you have a new release of Nix Packages, you can do: $ nix-env -f nixpkgs-version -u subversion This will only upgrade Subversion if there is a “newer” version in the new set of Nix expressions, as defined by some pretty arbitrary rules regarding ordering of version numbers (which generally do what you’d expect of them). To just unconditionally replace Subversion with whatever version is in the Nix expressions, use -i instead of -u; -i will remove whatever version is already installed. You can also upgrade all packages for which there are newer versions: $ nix-env -f nixpkgs-version -u '*' Sometimes it’s useful to be able to ask what nix-env would do, without actually doing it. For instance, to find out what packages would be upgraded by nix-env -u '*', you can do $ nix-env ... -u '*' --dry-run (dry run; not doing anything) upgrading `libxslt-1.1.0' to `libxslt-1.1.10' upgrading `graphviz-1.10' to `graphviz-1.12' upgrading `coreutils-5.0' to `coreutils-5.2.1'