Convert fhs-environments from DocBook to CommonMark

2020-12-16 14:51:43 -03:00
parent 23d5784770
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+# buildFHSUserEnv {#sec-fhs-environments}
+
+`buildFHSUserEnv` 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`.
+
+One can create a simple environment using a `shell.nix` like that:
+
+```nix
+{ pkgs ? import <nixpkgs> {} }:
+
+(pkgs.buildFHSUserEnv {
+  name = "simple-x11-env";
+  targetPkgs = pkgs: (with pkgs;
+    [ udev
+      alsaLib
+    ]) ++ (with pkgs.xorg;
+    [ libX11
+      libXcursor
+      libXrandr
+    ]);
+  multiPkgs = pkgs: (with pkgs;
+    [ udev
+      alsaLib
+    ]);
+  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.