buildFHSEnv

buildFHSEnv provides a way to build and run FHS-compatible lightweight sandboxes. It creates an isolated root with bound /nix/store, so its footprint in terms of disk space needed is quite small. This allows one to run software which is hard or unfeasible to patch for NixOS -- 3rd-party source trees with FHS assumptions, games distributed as tarballs, software with integrity checking and/or external self-updated binaries. It uses Linux namespaces feature to create temporary lightweight environments which are destroyed after all child processes exit, without root user rights requirement. Accepted arguments are:

name Environment name.
targetPkgs Packages to be installed for the main host's architecture (i.e. x86_64 on x86_64 installations). Along with libraries binaries are also installed.
multiPkgs Packages to be installed for all architectures supported by a host (i.e. i686 and x86_64 on x86_64 installations). Only libraries are installed by default.
extraBuildCommands Additional commands to be executed for finalizing the directory structure.
extraBuildCommandsMulti Like extraBuildCommands, but executed only on multilib architectures.
extraOutputsToInstall Additional derivation outputs to be linked for both target and multi-architecture packages.
extraInstallCommands Additional commands to be executed for finalizing the derivation with runner script.
runScript A command that would be executed inside the sandbox and passed all the command line arguments. It defaults to bash.
profile Optional script for /etc/profile within the sandbox.

One can create a simple environment using a shell.nix like that:

{ pkgs ? import <nixpkgs> {} }:

(pkgs.buildFHSEnv {
  name = "simple-x11-env";
  targetPkgs = pkgs: (with pkgs;
    [ udev
      alsa-lib
    ]) ++ (with pkgs.xorg;
    [ libX11
      libXcursor
      libXrandr
    ]);
  multiPkgs = pkgs: (with pkgs;
    [ udev
      alsa-lib
    ]);
  runScript = "bash";
}).env

Running nix-shell would then drop you into a shell with these libraries and binaries available. You can use this to run closed-source applications which expect FHS structure without hassles: simply change runScript to the application path, e.g. ./bin/start.sh -- relative paths are supported.

Additionally, the FHS builder links all relocated gsettings-schemas (the glib setup-hook moves them to share/gsettings-schemas/${name}/glib-2.0/schemas) to their standard FHS location. This means you don't need to wrap binaries with wrapGAppsHook.

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buildFHSEnv

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