Home Manager using Nix

This project provides a basic system for managing a user environment using the Nix package manager together with the Nix libraries found in Nixpkgs. Before attempting to use Home Manager please read the warning below.

Words of warning

This project is under development. I personally use it to manage several user configurations but it may fail catastrophically for you. So beware!

In some cases Home Manager cannot detect whether it will overwrite a previous manual configuration. For example, the Gnome Terminal module will write to your dconf store and cannot tell whether a configuration that it is about to be overwrite was from a previous Home Manager generation or from manual configuration.

Home Manager targets NixOS unstable and NixOS version 17.09 (the current stable version), it may or may not work on other Linux distributions and NixOS versions.

Also, the home-manager tool does not explicitly support rollbacks at the moment so if your home directory gets messed up you'll have to fix it yourself. See the rollbacks section for instructions on how to manually perform a rollback.

Now when your expectations have been built up and you are eager to try all this out you can go ahead and read the rest of this text.

Installation

Currently the easiest way to install Home Manager is as follows:

Make sure you have a working Nix installation. If you are not using NixOS then you may here have to run
```
$ mkdir -m 0755 -p /nix/var/nix/{profiles,gcroots}/per-user/$USER
```
since Home Manager uses these directories to manage your profile generations. On NixOS these should already be available.

Also make sure that your user is able to build and install Nix packages. For example, you should be able to successfully run a command like nix-instantiate '<nixpkgs>' -A hello. For a multi-user install of Nix this means that your user must be covered by the allowed-users Nix option. On NixOS you can control this option using the nix.allowedUsers system option.
Assign a temporary variable holding the URL to the appropriate archive. Typically this is
```
$ HM_PATH=https://github.com/rycee/home-manager/archive/master.tar.gz
```
or
```
$ HM_PATH=https://github.com/rycee/home-manager/archive/release-17.09.tar.gz
```
depending on whether you follow Nixpkgs unstable or version 17.09.

Create an initial Home Manager configuration file:

$ cat > ~/.config/nixpkgs/home.nix <<EOF
{
  programs.home-manager.enable = true;
  programs.home-manager.path = $HM_PATH;
}
EOF

Install Home Manager and create the first Home Manager generation:
```
$ nix-shell $HM_PATH -A install
```
Home Manager should now be active and available in your user environment.
If you do not plan on having Home Manager manage your shell configuration then you must source the
```
"$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"
```
file in your shell configuration. Unfortunately, we currently only support POSIX.2-like shells such as Bash or Z shell.

For example, if you use Bash then add
```
. "$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"
```
to your ~/.profile file.

Note, because the HM_PATH variable above points to the live Home Manager repository you will automatically get updates whenever you build a new generation. If you dislike automatic updates then perform a Git clone of the desired branch and instead do the above steps with HM_PATH set to the absolute path of your clone.

Usage

Home Manager is typically managed through the home-manager tool. This tool can, for example, apply configurations to your home directory, list user packages installed by the tool, and list the configuration generations.

As an example, let us expand the initial configuration file from the installation above to install the htop and fortune packages, install Emacs with a few extra packages enabled, install Firefox with the IcedTea plugin enabled, and enable the user gpg-agent service.

To satisfy the above setup we should elaborate the ~/.config/nixpkgs/home.nix file as follows:

{ pkgs, ... }:

{
  home.packages = [
    pkgs.htop
    pkgs.fortune
  ];

  programs.emacs = {
    enable = true;
    extraPackages = epkgs: [
      epkgs.nix-mode
      epkgs.magit
    ];
  };

  programs.firefox = {
    enable = true;
    enableIcedTea = true;
  };

  services.gpg-agent = {
    enable = true;
    defaultCacheTtl = 1800;
    enableSshSupport = true;
  };

  programs.home-manager = {
    enable = true;
    path = "…";
  };
}

To activate this configuration you can then run

$ home-manager switch

or if you are not feeling so lucky,

$ home-manager build

which will create a result link to a directory containing an activation script and the generated home directory files.

To see available configuration options with descriptions and usage examples run

$ man home-configuration.nix

Rollbacks

While the home-manager tool does not explicitly support rollbacks at the moment it is relatively easy to perform one manually. The steps to do so are

Run home-manager generations to determine which generation you wish to rollback to:

$ home-manager generations
2018-01-04 11:56 : id 765 -> /nix/store/kahm1rxk77mnvd2l8pfvd4jkkffk5ijk-home-manager-generation
2018-01-03 10:29 : id 764 -> /nix/store/2wsmsliqr5yynqkdyjzb1y57pr5q2lsj-home-manager-generation
2018-01-01 12:21 : id 763 -> /nix/store/mv960kl9chn2lal5q8lnqdp1ygxngcd1-home-manager-generation
2017-12-29 21:03 : id 762 -> /nix/store/6c0k1r03fxckql4vgqcn9ccb616ynb94-home-manager-generation
2017-12-25 18:51 : id 761 -> /nix/store/czc5y6vi1rvnkfv83cs3rn84jarcgsgh-home-manager-generation
…

Copy the Nix store path of the generation you chose, e.g.,
```
/nix/store/mv960kl9chn2lal5q8lnqdp1ygxngcd1-home-manager-generation
```
for generation 763.

Run the activate script inside the copied store path:

$ /nix/store/mv960kl9chn2lal5q8lnqdp1ygxngcd1-home-manager-generation/activate
Starting home manager activation
…

Keeping your ~ safe from harm

To configure programs and services Home Manager must write various things to your home directory. To prevent overwriting any existing files when switching to a new generation, Home Manager will attempt to detect collisions between existing files and generated files. If any such collision is detected the activation will terminate before changing anything on your computer.

For example, suppose you have a wonderful, painstakingly created ~/.gitconfig and add

{
  # …

  programs.git = {
    enable = true;
    userName = "Jane Doe";
    userEmail = "jane.doe@example.org";
  };

  # …
}

to your configuration. Attempting to switch to the generation will then result in

$ home-manager switch
…
Activating checkLinkTargets
Existing file '/home/jdoe/.gitconfig' is in the way
Please move the above files and try again

Graphical services

Home Manager includes a number of services intended to run in a graphical session, for example xscreensaver and dunst. Unfortunately, such services will not be started automatically unless you let Home Manager start your X session. That is, you have something like

{
  # …

  services.xserver.enable = true;

  # …
}

in your system configuration and

{
  # …

  xsession.enable = true;
  xsession.windowManager.command = "…";

  # …
}

in your Home Manager configuration.