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13.3.1 Essential Home Services

There are a few essential home services defined in (gnu services), they are mostly for internal use and are required to build a home environment, but some of them will be useful for the end user.

Scheme Variable: home-environment-variables-service-type

The service of this type will be instantiated by every home environment automatically by default, there is no need to define it, but someone may want to extend it with a list of pairs to set some environment variables. 

(list ("ENV_VAR1" . "value1")
      ("ENV_VAR2" . "value2"))

The easiest way to extend a service type, without defining a new service type is to use the simple-service helper from (gnu services). 

(simple-service 'some-useful-env-vars-service
		home-environment-variables-service-type
		`(("LESSHISTFILE" . "$XDG_CACHE_HOME/.lesshst")
                  ("SHELL" . ,(file-append zsh "/bin/zsh"))
                  ("USELESS_VAR" . #f)
                  ("_JAVA_AWT_WM_NONREPARENTING" . #t)))

If you include such a service in you home environment definition, it will add the following content to the setup-environment script (which is expected to be sourced by the login shell): 

export LESSHISTFILE=$XDG_CACHE_HOME/.lesshst
export SHELL=/gnu/store/2hsg15n644f0glrcbkb1kqknmmqdar03-zsh-5.8/bin/zsh
export _JAVA_AWT_WM_NONREPARENTING

Note: Make sure that module (gnu packages shells) is imported with use-modules or any other way, this namespace contains the definition of the zsh package, which is used in the example above.

The association list (see Association Lists in The GNU Guile Reference manual) is a data structure containing key-value pairs, for home-environment-variables-service-type the key is always a string, the value can be a string, string-valued gexp (see G-Expressions), file-like object (see file-like object) or boolean. For gexps, the variable will be set to the value of the gexp; for file-like objects, it will be set to the path of the file in the store (see The Store); for #t, it will export the variable without any value; and for #f, it will omit variable.

Scheme Variable: home-profile-service-type

The service of this type will be instantiated by every home environment automatically, there is no need to define it, but you may want to extend it with a list of packages if you want to install additional packages into your profile. Other services, which need to make some programs available to the user will also extend this service type.

The extension value is just a list of packages: 

(list htop vim emacs)

The same approach as simple-service (see simple-service) for home-environment-variables-service-type can be used here, too. Make sure that modules containing the specified packages are imported with use-modules. To find a package or information about its module use guix search (see Invoking guix package). Alternatively, specification->package can be used to get the package record from string without importing related module.

There are few more essential services, but users are not expected to extend them.

Scheme Variable: home-service-type

The root of home services DAG, it generates a folder, which later will be symlinked to ~/.guix-home, it contains configurations, profile with binaries and libraries, and some necessary scripts to glue things together.

Scheme Variable: home-run-on-first-login-service-type

The service of this type generates a Guile script, which is expected to be executed by the login shell. It is only executed if the special flag file inside XDG_RUNTIME_DIR hasn’t been created, this prevents redundant executions of the script if multiple login shells are spawned.

It can be extended with a gexp. However, to autostart an application, users should not use this service, in most cases it’s better to extend home-shepherd-service-type with a Shepherd service (see Shepherd Services), or extend the shell’s startup file with the required command using the appropriate service type.

Scheme Variable: home-files-service-type

The service of this type allows to specify a list of files, which will go to ~/.guix-home/files, usually this directory contains configuration files (to be more precise it contains symlinks to files in /gnu/store), which should be placed in $XDG_CONFIG_DIR or in rare cases in $HOME. It accepts extension values in the following format: 

`((".sway/config" ,sway-file-like-object)
  (".tmux.conf" ,(local-file "./tmux.conf")))

Each nested list contains two values: a subdirectory and file-like object. After building a home environment ~/.guix-home/files will be populated with apropiate content and all nested directories will be created accordingly, however, those files won’t go any further until some other service will do it. By default a home-symlink-manager-service-type, which creates necessary symlinks in home folder to files from ~/.guix-home/files and backs up already existing, but clashing configs and other things, is a part of essential home services (enabled by default), but it’s possible to use alternative services to implement more advanced use cases like read-only home. Feel free to experiment and share your results.

Scheme Variable: home-xdg-configuration-files-service-type

The service is very similiar to home-files-service-type (and actually extends it), but used for defining files, which will go to ~/.guix-home/files/.config, which will be symlinked to $XDG_CONFIG_DIR by home-symlink-manager-service-type (for example) during activation. It accepts extension values in the following format: 

`(("sway/config" ,sway-file-like-object)
  ;; -> ~/.guix-home/files/.config/sway/config
  ;; -> $XDG_CONFIG_DIR/sway/config (by symlink-manager)
  ("tmux/tmux.conf" ,(local-file "./tmux.conf")))
Scheme Variable: home-activation-service-type

The service of this type generates a guile script, which runs on every guix home reconfigure invocation or any other action, which leads to the activation of the home environment.

The service of this type generates a guile script, which will be executed during activation of home environment, and do a few following steps:

  1. Reads the content of files/ directory of current and pending home environments.
  2. Cleans up all symlinks created by symlink-manager on previous activation. Also, sub-directories, which become empty also will be cleaned up.
  3. Creates new symlinks the following way: It looks files/ directory (usually defined with home-files-service-type, home-xdg-configuration-files-service-type and maybe some others), takes the files from files/.config/ subdirectory and put respective links in XDG_CONFIG_DIR. For example symlink for files/.config/sway/config will end up in $XDG_CONFIG_DIR/sway/config. The rest files in files/ outside of files/.config/ subdirectory will be treated slightly different: symlink will just go to $HOME. files/.some-program/config will end up in $HOME/.some-program/config.
  4. If some sub-directories are missing, they will be created.
  5. If there is a clashing files on the way, they will be backed up.

symlink-manager is a part of essential home services and is enabled and used by default.

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