gnu: Move (gnu home-services) to (gnu home services).

* gnu/home-services/configuration.scm: Move the content ...
* gnu/home/services/configuration.scm: ... here.
* doc/guix.texi:
Replace (gnu home-services mcron) with (gnu home services mcron).
Replace (gnu home-services) with (gnu home services).
* gnu/home.scm:
Replace (gnu home-services fontutils) with (gnu services fontutils).
Replace (gnu home-services shells) with (gnu home services shells).
Replace (gnu home-services symlink-manager) with
(gnu home services symlink-manager).
Replace (gnu home-services xdg) with (gnu home services xdg).
* gnu/home-services/fontutils.scm: Rename to gnu/services/fontutils.scm.
* gnu/home-services/mcron.scm: Move to gnu/home/services/mcron.scm.
Replace (gnu home-services shepherd) with (gnu home services shepherd).
* gnu/home-services.scm (%service-type-path):
Search home services in "gnu/services".
* gnu/home-services/shells.scm: Replace (gnu home-services configuration) with
(gnu home services configuration).
Rename to gnu/home/services/shells.scm.
Replace (gnu home-services utils) with (gnu home services utils).
* gnu/home-services/shepherd.scm: Move to gnu/home/services/shepherd.scm.
* gnu/home-services/symlink-manager.scm:
Rename to gnu/home/services/symlink-manager.scm.
* gnu/home-services/utils.scm: Rename to gnu/home/services/utils.scm.
* gnu/home-services/xdg.scm: Rename to gnu/home/services/xdg.scm.
* guix/scripts/home/import.scm:
Replace (gnu home-services bash) with (gnu home services bash).
* gnu/home-services.scm: Update documentation string.
* doc/he-config-bare-bones.scm:
Apply new (gnu home-services ...) modules location.
* gnu/local.mk (GNU_SYSTEM_MODULES): Same.

8 files changed, 1887 insertions, 0 deletions

diff --git a/gnu/home/services/configuration.scm b/gnu/home/services/configuration.scm
new file mode 100644
index 0000000000..5e7743e7d6
--- /dev/null
+++ b/gnu/home/services/configuration.scm
@@ -0,0 +1,109 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services configuration)
+  #:use-module (gnu services configuration)
+  #:use-module (guix gexp)
+  #:use-module (srfi srfi-1)
+  #:use-module (ice-9 curried-definitions)
+  #:use-module (ice-9 match)
+  #:use-module (guix i18n)
+  #:use-module (guix diagnostics)
+
+  #:export (filter-configuration-fields
+
+            interpose
+            list-of
+
+            list-of-strings?
+            alist?
+            string-or-gexp?
+	    serialize-string-or-gexp
+	    text-config?
+            serialize-text-config
+            generic-serialize-alist-entry
+            generic-serialize-alist))
+
+(define* (filter-configuration-fields configuration-fields fields
+				      #:optional negate?)
+  "Retrieve the fields listed in FIELDS from CONFIGURATION-FIELDS.
+If NEGATE? is @code{#t}, retrieve all fields except FIELDS."
+  (filter (lambda (field)
+            (let ((member? (member (configuration-field-name field) fields)))
+              (if (not negate?) member? (not member?))))
+          configuration-fields))
+
+
+(define* (interpose ls  #:optional (delimiter "\n") (grammar 'infix))
+  "Same as @code{string-join}, but without join and string, returns an
+DELIMITER interposed LS.  Support 'infix and 'suffix GRAMMAR values."
+  (when (not (member grammar '(infix suffix)))
+    (raise
+     (formatted-message
+      (G_ "The GRAMMAR value must be 'infix or 'suffix, but ~a provided.")
+      grammar)))
+  (fold-right (lambda (e acc)
+		(cons e
+		      (if (and (null? acc) (eq? grammar 'infix))
+			  acc
+			  (cons delimiter acc))))
+	      '() ls))
+
+(define (list-of pred?)
+  "Return a procedure that takes a list and check if all the elements of
+the list result in @code{#t} when applying PRED? on them."
+    (lambda (x)
+      (if (list? x)
+          (every pred? x)
+          #f)))
+
+
+(define list-of-strings?
+  (list-of string?))
+
+(define alist? list?)
+
+(define (string-or-gexp? sg) (or (string? sg) (gexp? sg)))
+(define (serialize-string-or-gexp field-name val) "")
+
+(define (text-config? config)
+  (and (list? config) (every string-or-gexp? config)))
+(define (serialize-text-config field-name val)
+  #~(string-append #$@(interpose val "\n" 'suffix)))
+
+(define ((generic-serialize-alist-entry serialize-field) entry)
+  "Apply the SERIALIZE-FIELD procedure on the field and value of ENTRY."
+  (match entry
+    ((field . val) (serialize-field field val))))
+
+(define (generic-serialize-alist combine serialize-field fields)
+  "Generate a configuration from an association list FIELDS.
+
+SERIALIZE-FIELD is a procedure that takes two arguments, it will be
+applied on the fields and values of FIELDS using the
+@code{generic-serialize-alist-entry} procedure.
+
+COMBINE is a procedure that takes one or more arguments and combines
+all the alist entries into one value, @code{string-append} or
+@code{append} are usually good candidates for this.
+
+See the @code{serialize-alist} procedure in `@code{(gnu home-services
+version-control}' for an example usage.)}"
+  (apply combine
+         (map (generic-serialize-alist-entry serialize-field) fields)))
diff --git a/gnu/home/services/fontutils.scm b/gnu/home/services/fontutils.scm
new file mode 100644
index 0000000000..72a84fdecd
--- /dev/null
+++ b/gnu/home/services/fontutils.scm
@@ -0,0 +1,65 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services fontutils)
+  #:use-module (gnu home-services)
+  #:use-module (gnu packages fontutils)
+  #:use-module (guix gexp)
+
+  #:export (home-fontconfig-service-type))
+
+;;; Commentary:
+;;;
+;;; Services related to fonts.  home-fontconfig service provides
+;;; fontconfig configuration, which allows fc-* utilities to find
+;;; fonts in Guix Home's profile and regenerates font cache on
+;;; activation.
+;;;
+;;; Code:
+
+(define (add-fontconfig-config-file he-symlink-path)
+  `(("config/fontconfig/fonts.conf"
+     ,(mixed-text-file
+       "fonts.conf"
+       "<?xml version='1.0'?>
+<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
+<fontconfig>
+  <dir>~/.guix-home/profile/share/fonts</dir>
+</fontconfig>"))))
+
+(define (regenerate-font-cache-gexp _)
+  `(("profile/share/fonts"
+     ,#~(system* #$(file-append fontconfig "/bin/fc-cache") "-fv"))))
+
+(define home-fontconfig-service-type
+  (service-type (name 'home-fontconfig)
+                (extensions
+                 (list (service-extension
+                        home-files-service-type
+                        add-fontconfig-config-file)
+                       (service-extension
+                        home-run-on-change-service-type
+                        regenerate-font-cache-gexp)
+                       (service-extension
+                        home-profile-service-type
+                        (const (list fontconfig)))))
+                (default-value #f)
+                (description
+                 "Provides configuration file for fontconfig and make
+fc-* utilities aware of font packages installed in Guix Home's profile.")))
diff --git a/gnu/home/services/mcron.scm b/gnu/home/services/mcron.scm
new file mode 100644
index 0000000000..cc6faac47f
--- /dev/null
+++ b/gnu/home/services/mcron.scm
@@ -0,0 +1,115 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services mcron)
+  #:use-module (gnu packages guile-xyz)
+  #:use-module (gnu home-services)
+  #:use-module (gnu services shepherd)
+  #:use-module (gnu home services shepherd)
+  #:use-module (guix records)
+  #:use-module (guix gexp)
+  #:use-module (srfi srfi-1)
+  #:use-module (ice-9 match)
+
+  #:export (home-mcron-configuration
+            home-mcron-service-type))
+
+;;; Commentary:
+;;
+;; Service for the GNU mcron cron job manager.
+;;
+;; Example configuration, the first job runs mbsync once every ten
+;; minutes, the second one writes "Mcron service" to ~/mcron-file once
+;; every minute.
+;;
+;; (service home-mcron-service-type
+;;            (home-mcron-configuration
+;;             (jobs (list #~(job '(next-minute
+;;                                  (range 0 60 10))
+;;                                (lambda ()
+;;                                  (system* "mbsync" "--all")))
+;;                         #~(job next-minute-from
+;;                                (lambda ()
+;;                                  (call-with-output-file (string-append (getenv "HOME")
+;;                                                                        "/mcron-file")
+;;                                    (lambda (port)
+;;                                      (display "Mcron service" port)))))))))
+;;
+;;; Code:
+
+(define-record-type* <home-mcron-configuration> home-mcron-configuration
+  make-home-mcron-configuration
+  home-mcron-configuration?
+  (package home-mcron-configuration-package ; package
+           (default mcron))
+  (jobs home-mcron-configuration-jobs   ; list of jobs
+        (default '())))
+
+(define job-files (@@ (gnu services mcron) job-files))
+(define shepherd-schedule-action
+  (@@ (gnu services mcron) shepherd-schedule-action))
+
+(define home-mcron-shepherd-services
+  (match-lambda
+    (($ <home-mcron-configuration> mcron '()) ; no jobs to run
+     '())
+    (($ <home-mcron-configuration> mcron jobs)
+     (let ((files (job-files mcron jobs)))
+       (list (shepherd-service
+              (documentation "User cron jobs.")
+              (provision '(mcron))
+              (modules `((srfi srfi-1)
+                         (srfi srfi-26)
+                         (ice-9 popen)            ; for the 'schedule' action
+                         (ice-9 rdelim)
+                         (ice-9 match)
+                         ,@%default-modules))
+              (start #~(make-forkexec-constructor
+                        (list #$(file-append mcron "/bin/mcron") #$@files)
+                        #:log-file (string-append
+                                    (or (getenv "XDG_LOG_HOME")
+                                        (format #f "~a/.local/var/log"
+                                                (getenv "HOME")))
+                                    "/mcron.log")))
+              (stop #~(make-kill-destructor))
+              (actions
+               (list (shepherd-schedule-action mcron files)))))))))
+
+(define home-mcron-profile (compose list home-mcron-configuration-package))
+
+(define (home-mcron-extend config jobs)
+  (home-mcron-configuration
+   (inherit config)
+   (jobs (append (home-mcron-configuration-jobs config)
+                 jobs))))
+
+(define home-mcron-service-type
+  (service-type (name 'home-mcron)
+                (extensions
+                 (list (service-extension
+                        home-shepherd-service-type
+                        home-mcron-shepherd-services)
+                       (service-extension
+                        home-profile-service-type
+                        home-mcron-profile)))
+                (compose concatenate)
+                (extend home-mcron-extend)
+                (default-value (home-mcron-configuration))
+                (description
+                 "Install and configure the GNU mcron cron job manager.")))
diff --git a/gnu/home/services/shells.scm b/gnu/home/services/shells.scm
new file mode 100644
index 0000000000..2308371dd0
--- /dev/null
+++ b/gnu/home/services/shells.scm
@@ -0,0 +1,634 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services shells)
+  #:use-module (gnu services configuration)
+  #:use-module (gnu home services configuration)
+  #:use-module (gnu home services utils)
+  #:use-module (gnu home-services)
+  #:use-module (gnu packages shells)
+  #:use-module (gnu packages bash)
+  #:use-module (guix gexp)
+  #:use-module (guix packages)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:use-module (ice-9 match)
+
+  #:export (home-shell-profile-service-type
+            home-shell-profile-configuration
+
+            home-bash-service-type
+            home-bash-configuration
+            home-bash-extension
+
+            home-zsh-service-type
+            home-zsh-configuration
+            home-zsh-extension
+
+            home-fish-service-type
+            home-fish-configuration
+            home-fish-extension))
+
+;;; Commentary:
+;;;
+;;; This module contains shell related services like Zsh.
+;;;
+;;; Code:
+
+
+;;;
+;;; Shell profile.
+;;;
+
+(define path? string?)
+(define (serialize-path field-name val) val)
+
+(define-configuration home-shell-profile-configuration
+  (profile
+   (text-config '())
+   "\
+@code{home-shell-profile} is instantiated automatically by
+@code{home-environment}, DO NOT create this service manually, it can
+only be extended.
+
+@code{profile} is a list of strings or gexps, which will go to
+@file{~/.profile}.  By default @file{~/.profile} contains the
+initialization code, which have to be evaluated by login shell to make
+home-environment's profile avaliable to the user, but other commands
+can be added to the file if it is really necessary.
+
+In most cases shell's configuration files are preferred places for
+user's customizations.  Extend home-shell-profile service only if you
+really know what you do."))
+
+(define (add-shell-profile-file config)
+  `(("profile"
+     ,(mixed-text-file
+       "shell-profile"
+       "\
+HOME_ENVIRONMENT=$HOME/.guix-home
+. $HOME_ENVIRONMENT/setup-environment
+$HOME_ENVIRONMENT/on-first-login\n"
+       (serialize-configuration
+        config
+        (filter-configuration-fields
+         home-shell-profile-configuration-fields '(profile)))))))
+
+(define (add-profile-extensions config extensions)
+  (home-shell-profile-configuration
+   (inherit config)
+   (profile
+    (append (home-shell-profile-configuration-profile config)
+            extensions))))
+
+(define home-shell-profile-service-type
+  (service-type (name 'home-shell-profile)
+                (extensions
+                 (list (service-extension
+                        home-files-service-type
+                        add-shell-profile-file)))
+                (compose concatenate)
+                (extend add-profile-extensions)
+                (default-value (home-shell-profile-configuration))
+                (description "Create @file{~/.profile}, which is used
+for environment initialization of POSIX compliant login shells.  This
+service type can be extended with a list of strings or gexps.")))
+
+(define (serialize-boolean field-name val) "")
+(define (serialize-posix-env-vars field-name val)
+  #~(string-append
+     #$@(map
+         (match-lambda
+           ((key . #f)
+            "")
+           ((key . #t)
+            #~(string-append "export " #$key "\n"))
+           ((key . value)
+            #~(string-append "export " #$key "=" #$value "\n")))
+         val)))
+
+
+;;;
+;;; Zsh.
+;;;
+
+(define-configuration home-zsh-configuration
+  (package
+    (package zsh)
+    "The Zsh package to use.")
+  (xdg-flavor?
+   (boolean #t)
+   "Place all the configs to @file{$XDG_CONFIG_HOME/zsh}.  Makes
+@file{~/.zshenv} to set @env{ZDOTDIR} to @file{$XDG_CONFIG_HOME/zsh}.
+Shell startup process will continue with
+@file{$XDG_CONFIG_HOME/zsh/.zshenv}.")
+  (environment-variables
+   (alist '())
+   "Association list of environment variables to set for the Zsh session."
+   serialize-posix-env-vars)
+  (zshenv
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.zshenv}.
+Used for setting user's shell environment variables.  Must not contain
+commands assuming the presence of tty or producing output.  Will be
+read always.  Will be read before any other file in @env{ZDOTDIR}.")
+  (zprofile
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.zprofile}.
+Used for executing user's commands at start of login shell (In most
+cases the shell started on tty just after login).  Will be read before
+@file{.zlogin}.")
+  (zshrc
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.zshrc}.
+Used for executing user's commands at start of interactive shell (The
+shell for interactive usage started by typing @code{zsh} or by
+terminal app or any other program).")
+  (zlogin
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.zlogin}.
+Used for executing user's commands at the end of starting process of
+login shell.")
+  (zlogout
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.zlogout}.
+Used for executing user's commands at the exit of login shell.  It
+won't be read in some cases (if the shell terminates by exec'ing
+another process for example)."))
+
+(define (add-zsh-configuration config)
+  (let* ((xdg-flavor? (home-zsh-configuration-xdg-flavor? config)))
+
+    (define prefix-file
+      (cut string-append
+        (if xdg-flavor?
+            "config/zsh/."
+            "") <>))
+
+    (define (filter-fields field)
+      (filter-configuration-fields home-zsh-configuration-fields
+                                   (list field)))
+
+    (define (serialize-field field)
+      (serialize-configuration
+       config
+       (filter-fields field)))
+
+    (define (file-if-not-empty field)
+      (let ((file-name (symbol->string field))
+            (field-obj (car (filter-fields field))))
+        (if (not (null? ((configuration-field-getter field-obj) config)))
+            `(,(prefix-file file-name)
+              ,(mixed-text-file
+                file-name
+                (serialize-field field)))
+            '())))
+
+    (filter
+     (compose not null?)
+     `(,(if xdg-flavor?
+            `("zshenv"
+              ,(mixed-text-file
+                "auxiliary-zshenv"
+                (if xdg-flavor?
+                    "source ${XDG_CONFIG_HOME:-$HOME/.config}/zsh/.zshenv\n"
+                    "")))
+            '())
+       (,(prefix-file "zshenv")
+        ,(mixed-text-file
+          "zshenv"
+          (if xdg-flavor?
+              "export ZDOTDIR=${XDG_CONFIG_HOME:-$HOME/.config}/zsh\n"
+              "")
+          (serialize-field 'zshenv)
+          (serialize-field 'environment-variables)))
+       (,(prefix-file "zprofile")
+        ,(mixed-text-file
+          "zprofile"
+          "\
+# Setups system and user profiles and related variables
+source /etc/profile
+# Setups home environment profile
+source ~/.profile
+
+# It's only necessary if zsh is a login shell, otherwise profiles will
+# be already sourced by bash
+"
+          (serialize-field 'zprofile)))
+
+       ,@(list (file-if-not-empty 'zshrc)
+               (file-if-not-empty 'zlogin)
+               (file-if-not-empty 'zlogout))))))
+
+(define (add-zsh-packages config)
+  (list (home-zsh-configuration-package config)))
+
+(define-configuration/no-serialization home-zsh-extension
+  (environment-variables
+   (alist '())
+   "Association list of environment variables to set.")
+  (zshrc
+   (text-config '())
+   "List of strings or gexps.")
+  (zshenv
+   (text-config '())
+   "List of strings or gexps.")
+  (zprofile
+   (text-config '())
+   "List of strings or gexps.")
+  (zlogin
+   (text-config '())
+   "List of strings or gexps.")
+  (zlogout
+   (text-config '())
+   "List of strings or gexps."))
+
+(define (home-zsh-extensions original-config extension-configs)
+  (home-zsh-configuration
+   (inherit original-config)
+   (environment-variables
+    (append (home-zsh-configuration-environment-variables original-config)
+            (append-map
+             home-zsh-extension-environment-variables extension-configs)))
+   (zshrc
+    (append (home-zsh-configuration-zshrc original-config)
+            (append-map
+             home-zsh-extension-zshrc extension-configs)))
+   (zshenv
+    (append (home-zsh-configuration-zshenv original-config)
+            (append-map
+             home-zsh-extension-zshenv extension-configs)))
+   (zprofile
+    (append (home-zsh-configuration-zprofile original-config)
+            (append-map
+             home-zsh-extension-zprofile extension-configs)))
+   (zlogin
+    (append (home-zsh-configuration-zlogin original-config)
+            (append-map
+             home-zsh-extension-zlogin extension-configs)))
+   (zlogout
+    (append (home-zsh-configuration-zlogout original-config)
+            (append-map
+             home-zsh-extension-zlogout extension-configs)))))
+
+(define home-zsh-service-type
+  (service-type (name 'home-zsh)
+                (extensions
+                 (list (service-extension
+                        home-files-service-type
+                        add-zsh-configuration)
+                       (service-extension
+                        home-profile-service-type
+                        add-zsh-packages)))
+                (compose identity)
+                (extend home-zsh-extensions)
+                (default-value (home-zsh-configuration))
+                (description "Install and configure Zsh.")))
+
+
+;;;
+;;; Bash.
+;;;
+
+(define-configuration home-bash-configuration
+  (package
+   (package bash)
+   "The Bash package to use.")
+  (guix-defaults?
+   (boolean #t)
+   "Add sane defaults like reading @file{/etc/bashrc}, coloring output
+for @code{ls} provided by guix to @file{.bashrc}.")
+  (environment-variables
+   (alist '())
+   "Association list of environment variables to set for the Bash session."
+   serialize-posix-env-vars)
+  (bash-profile
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.bash_profile}.
+Used for executing user's commands at start of login shell (In most
+cases the shell started on tty just after login).  @file{.bash_login}
+won't be ever read, because @file{.bash_profile} always present.")
+  (bashrc
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.bashrc}.
+Used for executing user's commands at start of interactive shell (The
+shell for interactive usage started by typing @code{bash} or by
+terminal app or any other program).")
+  (bash-logout
+   (text-config '())
+   "List of strings or gexps, which will be added to @file{.bash_logout}.
+Used for executing user's commands at the exit of login shell.  It
+won't be read in some cases (if the shell terminates by exec'ing
+another process for example)."))
+
+;; TODO: Use value from (gnu system shadow)
+(define guix-bashrc
+  "\
+# Bash initialization for interactive non-login shells and
+# for remote shells (info \"(bash) Bash Startup Files\").
+
+# Export 'SHELL' to child processes.  Programs such as 'screen'
+# honor it and otherwise use /bin/sh.
+export SHELL
+
+if [[ $- != *i* ]]
+then
+    # We are being invoked from a non-interactive shell.  If this
+    # is an SSH session (as in \"ssh host command\"), source
+    # /etc/profile so we get PATH and other essential variables.
+    [[ -n \"$SSH_CLIENT\" ]] && source /etc/profile
+
+    # Don't do anything else.
+    return
+fi
+
+# Source the system-wide file.
+source /etc/bashrc
+
+# Adjust the prompt depending on whether we're in 'guix environment'.
+if [ -n \"$GUIX_ENVIRONMENT\" ]
+then
+    PS1='\\u@\\h \\w [env]\\$ '
+else
+    PS1='\\u@\\h \\w\\$ '
+fi
+alias ls='ls -p --color=auto'
+alias ll='ls -l'
+alias grep='grep --color=auto'\n")
+
+(define (add-bash-configuration config)
+  (define (filter-fields field)
+    (filter-configuration-fields home-bash-configuration-fields
+                                 (list field)))
+
+  (define (serialize-field field)
+    (serialize-configuration
+     config
+     (filter-fields field)))
+
+  (define* (file-if-not-empty field #:optional (extra-content #f))
+    (let ((file-name (symbol->string field))
+          (field-obj (car (filter-fields field))))
+      (if (or extra-content
+              (not (null? ((configuration-field-getter field-obj) config))))
+          `(,(object->snake-case-string file-name)
+            ,(mixed-text-file
+              (object->snake-case-string file-name)
+              (if extra-content extra-content "")
+              (serialize-field field)))
+          '())))
+
+  (filter
+   (compose not null?)
+   `(("bash_profile"
+      ,(mixed-text-file
+        "bash_profile"
+        "\
+# Setups system and user profiles and related variables
+# /etc/profile will be sourced by bash automatically
+# Setups home environment profile
+if [ -f ~/.profile ]; then source ~/.profile; fi
+
+# Honor per-interactive-shell startup file
+if [ -f ~/.bashrc ]; then source ~/.bashrc; fi
+"
+        (serialize-field 'bash-profile)
+        (serialize-field 'environment-variables)))
+
+     ,@(list (file-if-not-empty
+              'bashrc
+              (if (home-bash-configuration-guix-defaults? config)
+                  guix-bashrc
+                  #f))
+             (file-if-not-empty 'bash-logout)))))
+
+(define (add-bash-packages config)
+  (list (home-bash-configuration-package config)))
+
+(define-configuration/no-serialization home-bash-extension
+  (environment-variables
+   (alist '())
+   "Association list of environment variables to set.")
+  (bash-profile
+   (text-config '())
+   "List of strings or gexps.")
+  (bashrc
+   (text-config '())
+   "List of strings or gexps.")
+  (bash-logout
+   (text-config '())
+   "List of strings or gexps."))
+
+(define (home-bash-extensions original-config extension-configs)
+  (home-bash-configuration
+   (inherit original-config)
+   (environment-variables
+    (append (home-bash-configuration-environment-variables original-config)
+            (append-map
+             home-bash-extension-environment-variables extension-configs)))
+   (bash-profile
+    (append (home-bash-configuration-bash-profile original-config)
+            (append-map
+             home-bash-extension-bash-profile extension-configs)))
+   (bashrc
+    (append (home-bash-configuration-bashrc original-config)
+            (append-map
+             home-bash-extension-bashrc extension-configs)))
+   (bash-logout
+    (append (home-bash-configuration-bash-logout original-config)
+            (append-map
+             home-bash-extension-bash-logout extension-configs)))))
+
+(define home-bash-service-type
+  (service-type (name 'home-bash)
+                (extensions
+                 (list (service-extension
+                        home-files-service-type
+                        add-bash-configuration)
+                       (service-extension
+                        home-profile-service-type
+                        add-bash-packages)))
+                (compose identity)
+                (extend home-bash-extensions)
+                (default-value (home-bash-configuration))
+                (description "Install and configure GNU Bash.")))
+
+
+;;;
+;;; Fish.
+;;;
+
+(define (serialize-fish-aliases field-name val)
+  #~(string-append
+     #$@(map (match-lambda
+               ((key . value)
+                #~(string-append "alias " #$key " \"" #$value "\"\n"))
+               (_ ""))
+             val)))
+
+(define (serialize-fish-abbreviations field-name val)
+  #~(string-append
+     #$@(map (match-lambda
+               ((key . value)
+                #~(string-append "abbr --add " #$key " " #$value "\n"))
+               (_ ""))
+             val)))
+
+(define (serialize-fish-env-vars field-name val)
+  #~(string-append
+     #$@(map (match-lambda
+               ((key . #f)
+                "")
+               ((key . #t)
+                #~(string-append "set " #$key "\n"))
+               ((key . value)
+                #~(string-append "set " #$key " "  #$value "\n")))
+             val)))
+
+(define-configuration home-fish-configuration
+  (package
+    (package fish)
+    "The Fish package to use.")
+  (config
+   (text-config '())
+   "List of strings or gexps, which will be added to
+@file{$XDG_CONFIG_HOME/fish/config.fish}.")
+  (environment-variables
+   (alist '())
+   "Association list of environment variables to set in Fish."
+   serialize-fish-env-vars)
+  (aliases
+   (alist '())
+   "Association list of aliases for Fish, both the key and the value
+should be a string.  An alias is just a simple function that wraps a
+command, If you want something more akin to @dfn{aliases} in POSIX
+shells, see the @code{abbreviations} field."
+   serialize-fish-aliases)
+  (abbreviations
+   (alist '())
+   "Association list of abbreviations for Fish.  These are words that,
+when typed in the shell, will automatically expand to the full text."
+   serialize-fish-abbreviations))
+
+(define (fish-files-service config)
+  `(("config/fish/config.fish"
+     ,(mixed-text-file
+       "fish-config.fish"
+       #~(string-append "\
+# if we haven't sourced the login config, do it
+status --is-login; and not set -q __fish_login_config_sourced
+and begin
+
+  set --prepend fish_function_path "
+                        #$fish-foreign-env
+                        "/share/fish/functions
+  fenv source $HOME/.profile
+  set -e fish_function_path[1]
+
+  set -g __fish_login_config_sourced 1
+
+end\n\n")
+       (serialize-configuration
+        config
+        home-fish-configuration-fields)))))
+
+(define (fish-profile-service config)
+  (list (home-fish-configuration-package config)))
+
+(define-configuration/no-serialization home-fish-extension
+  (config
+   (text-config '())
+   "List of strings or gexps for extending the Fish initialization file.")
+  (environment-variables
+   (alist '())
+   "Association list of environment variables to set.")
+  (aliases
+   (alist '())
+   "Association list of Fish aliases.")
+  (abbreviations
+   (alist '())
+   "Association list of Fish abbreviations."))
+
+(define (home-fish-extensions original-config extension-configs)
+  (home-fish-configuration
+   (inherit original-config)
+   (config
+    (append (home-fish-configuration-config original-config)
+            (append-map
+             home-fish-extension-config extension-configs)))
+   (environment-variables
+    (append (home-fish-configuration-environment-variables original-config)
+            (append-map
+             home-fish-extension-environment-variables extension-configs)))
+   (aliases
+    (append (home-fish-configuration-aliases original-config)
+            (append-map
+             home-fish-extension-aliases extension-configs)))
+   (abbreviations
+    (append (home-fish-configuration-abbreviations original-config)
+            (append-map
+             home-fish-extension-abbreviations extension-configs)))))
+
+;; TODO: Support for generating completion files
+;; TODO: Support for installing plugins
+(define home-fish-service-type
+  (service-type (name 'home-fish)
+                (extensions
+                 (list (service-extension
+                        home-files-service-type
+                        fish-files-service)
+                       (service-extension
+                        home-profile-service-type
+                        fish-profile-service)))
+                (compose identity)
+                (extend home-fish-extensions)
+                (default-value (home-fish-configuration))
+                (description "\
+Install and configure Fish, the friendly interactive shell.")))
+
+
+(define (generate-home-shell-profile-documentation)
+  (generate-documentation
+   `((home-shell-profile-configuration
+      ,home-shell-profile-configuration-fields))
+   'home-shell-profile-configuration))
+
+(define (generate-home-bash-documentation)
+  (generate-documentation
+   `((home-bash-configuration
+      ,home-bash-configuration-fields))
+   'home-bash-configuration))
+
+(define (generate-home-zsh-documentation)
+  (generate-documentation
+   `((home-zsh-configuration
+      ,home-zsh-configuration-fields))
+   'home-zsh-configuration))
+
+(define (generate-home-fish-documentation)
+  (string-append
+   (generate-documentation
+    `((home-fish-configuration
+       ,home-fish-configuration-fields))
+    'home-fish-configuration)
+   "\n\n"
+   (generate-documentation
+    `((home-fish-extension
+       ,home-fish-extension-fields))
+    'home-fish-extension)))
diff --git a/gnu/home/services/shepherd.scm b/gnu/home/services/shepherd.scm
new file mode 100644
index 0000000000..1a3e849bb2
--- /dev/null
+++ b/gnu/home/services/shepherd.scm
@@ -0,0 +1,134 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services shepherd)
+  #:use-module (gnu home-services)
+  #:use-module (gnu packages admin)
+  #:use-module (gnu services shepherd)
+  #:use-module (guix sets)
+  #:use-module (guix gexp)
+  #:use-module (guix records)
+
+  #:use-module (srfi srfi-1)
+
+  #:export (home-shepherd-service-type
+            home-shepherd-configuration)
+  #:re-export (shepherd-service
+               shepherd-action))
+
+(define-record-type* <home-shepherd-configuration>
+  home-shepherd-configuration make-home-shepherd-configuration
+  home-shepherd-configuration?
+  (shepherd home-shepherd-configuration-shepherd
+            (default shepherd)) ; package
+  (auto-start? home-shepherd-configuration-auto-start?
+               (default #t))
+  (services home-shepherd-configuration-services
+            (default '())))
+
+(define (home-shepherd-configuration-file services shepherd)
+  "Return the shepherd configuration file for SERVICES.  SHEPHERD is used
+as shepherd package."
+  (assert-valid-graph services)
+
+  (let ((files (map shepherd-service-file services))
+        ;; TODO: Add compilation of services, it can improve start
+        ;; time.
+        ;; (scm->go (cute scm->go <> shepherd))
+        )
+    (define config
+      #~(begin
+          (use-modules (srfi srfi-34)
+                       (system repl error-handling))
+          (apply
+           register-services
+           (map
+            (lambda (file) (load file))
+            '#$files))
+          (action 'root 'daemonize)
+          (format #t "Starting services...~%")
+          (for-each
+           (lambda (service) (start service))
+           '#$(append-map shepherd-service-provision
+                          (filter shepherd-service-auto-start?
+                                  services)))
+          (newline)))
+
+    (scheme-file "shepherd.conf" config)))
+
+(define (launch-shepherd-gexp config)
+  (let* ((shepherd (home-shepherd-configuration-shepherd config))
+         (services (home-shepherd-configuration-services config)))
+    (if (home-shepherd-configuration-auto-start? config)
+        (with-imported-modules '((guix build utils))
+          #~(let ((log-dir (or (getenv "XDG_LOG_HOME")
+                               (format #f "~a/.local/var/log" (getenv "HOME")))))
+              ((@ (guix build utils) mkdir-p) log-dir)
+              (system*
+               #$(file-append shepherd "/bin/shepherd")
+               "--logfile"
+               (string-append
+                log-dir
+                "/shepherd.log")
+               "--config"
+               #$(home-shepherd-configuration-file services shepherd))))
+        #~"")))
+
+(define (reload-configuration-gexp config)
+  (let* ((shepherd (home-shepherd-configuration-shepherd config))
+         (services (home-shepherd-configuration-services config)))
+    #~(system*
+       #$(file-append shepherd "/bin/herd")
+       "load" "root"
+       #$(home-shepherd-configuration-file services shepherd))))
+
+(define (ensure-shepherd-gexp config)
+  #~(if (file-exists?
+         (string-append
+          (or (getenv "XDG_RUNTIME_DIR")
+              (format #f "/run/user/~a" (getuid)))
+          "/shepherd/socket"))
+        #$(reload-configuration-gexp config)
+        #$(launch-shepherd-gexp config)))
+
+(define-public home-shepherd-service-type
+  (service-type (name 'home-shepherd)
+                (extensions
+                 (list (service-extension
+                        home-run-on-first-login-service-type
+                        launch-shepherd-gexp)
+                       (service-extension
+                        home-activation-service-type
+                        ensure-shepherd-gexp)
+                       (service-extension
+                        home-profile-service-type
+                        (lambda (config)
+                          `(,(home-shepherd-configuration-shepherd config))))))
+                (compose concatenate)
+                (extend
+                 (lambda (config extra-services)
+                   (home-shepherd-configuration
+                    (inherit config)
+                    (services
+                     (append (home-shepherd-configuration-services config)
+                             extra-services)))))
+                (default-value (home-shepherd-configuration))
+                (description "Configure and install userland Shepherd.")))
+
+
diff --git a/gnu/home/services/symlink-manager.scm b/gnu/home/services/symlink-manager.scm
new file mode 100644
index 0000000000..d53e8f5046
--- /dev/null
+++ b/gnu/home/services/symlink-manager.scm
@@ -0,0 +1,247 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services symlink-manager)
+  #:use-module (gnu home-services)
+  #:use-module (guix gexp)
+
+  #:export (home-symlink-manager-service-type))
+
+;;; Comment:
+;;;
+;;; symlink-manager cares about configuration files: it backs up files
+;;; created by user, removes symlinks and directories created by a
+;;; previous generation, and creates new directories and symlinks to
+;;; configuration files according to the content of files/ directory
+;;; (created by home-files-service) of the current home environment
+;;; generation.
+;;;
+;;; Code:
+
+(define (update-symlinks-script)
+  (program-file
+   "update-symlinks"
+   #~(begin
+       (use-modules (ice-9 ftw)
+                    (ice-9 curried-definitions)
+                    (ice-9 match)
+                    (srfi srfi-1))
+       (define ((simplify-file-tree parent) file)
+         "Convert the result produced by `file-system-tree' to less
+verbose and more suitable for further processing format.
+
+Extract dir/file info from stat and compose a relative path to the
+root of the file tree.
+
+Sample output:
+
+((dir . \".\")
+ ((dir . \"config\")
+  ((dir . \"config/fontconfig\")
+   (file . \"config/fontconfig/fonts.conf\"))
+  ((dir . \"config/isync\")
+   (file . \"config/isync/mbsyncrc\"))))
+"
+         (match file
+           ((name stat) `(file . ,(string-append parent name)))
+           ((name stat children ...)
+            (cons `(dir . ,(string-append parent name))
+                  (map (simplify-file-tree
+                        (if (equal? name ".")
+                            ""
+                            (string-append parent name "/")))
+                       children)))))
+
+       (define ((file-tree-traverse preordering) node)
+         "Traverses the file tree in different orders, depending on PREORDERING.
+
+if PREORDERING is @code{#t} resulting list will contain directories
+before files located in those directories, otherwise directory will
+appear only after all nested items already listed."
+         (let ((prepend (lambda (a b) (append b a))))
+           (match node
+             (('file . path) (list node))
+             ((('dir . path) . rest)
+              ((if preordering append prepend)
+               (list (cons 'dir path))
+               (append-map (file-tree-traverse preordering) rest))))))
+
+       (use-modules (guix build utils))
+
+       (let* ((config-home    (or (getenv "XDG_CONFIG_HOME")
+                                  (string-append (getenv "HOME") "/.config")))
+
+              (he-path (string-append (getenv "HOME") "/.guix-home"))
+              (new-he-path (string-append he-path ".new"))
+              (new-home (getenv "GUIX_NEW_HOME"))
+              (old-home (getenv "GUIX_OLD_HOME"))
+
+              (new-files-path (string-append new-home "/files"))
+              ;; Trailing dot is required, because files itself is symlink and
+              ;; to make file-system-tree works it should be a directory.
+              (new-files-dir-path (string-append new-files-path "/."))
+
+              (home-path (getenv "HOME"))
+              (backup-dir (string-append home-path "/"
+                                         (number->string (current-time))
+                                         "-guix-home-legacy-configs-backup"))
+
+              (old-tree (if old-home
+                          ((simplify-file-tree "")
+                           (file-system-tree
+                            (string-append old-home "/files/.")))
+                          #f))
+              (new-tree ((simplify-file-tree "")
+                         (file-system-tree new-files-dir-path)))
+
+              (get-source-path
+               (lambda (path)
+                 (readlink (string-append new-files-path "/" path))))
+
+              (get-target-path
+               (lambda (path)
+                 (string-append home-path "/." path)))
+
+              (get-backup-path
+               (lambda (path)
+                 (string-append backup-dir "/." path)))
+
+              (directory?
+               (lambda (path)
+                 (equal? (stat:type (stat path)) 'directory)))
+
+              (empty-directory?
+               (lambda (dir)
+                 (equal? (scandir dir) '("." ".."))))
+
+              (symlink-to-store?
+               (lambda (path)
+                 (and
+                  (equal? (stat:type (lstat path)) 'symlink)
+                  (store-file-name? (readlink path)))))
+
+              (backup-file
+               (lambda (path)
+                 (mkdir-p backup-dir)
+                 (format #t "Backing up ~a..." (get-target-path path))
+                 (mkdir-p (dirname (get-backup-path path)))
+                 (rename-file (get-target-path path) (get-backup-path path))
+                 (display " done\n")))
+
+              (cleanup-symlinks
+               (lambda ()
+                 (let ((to-delete ((file-tree-traverse #f) old-tree)))
+                   (display
+                    "Cleaning up symlinks from previous home-environment.\n\n")
+                   (map
+                    (match-lambda
+                      (('dir . ".")
+                       (display "Cleanup finished.\n\n"))
+
+                      (('dir . path)
+                       (if (and
+                            (file-exists? (get-target-path path))
+                            (directory? (get-target-path path))
+                            (empty-directory? (get-target-path path)))
+                           (begin
+                             (format #t "Removing ~a..."
+                                     (get-target-path path))
+                             (rmdir (get-target-path path))
+                             (display " done\n"))
+                           (format
+                            #t "Skipping ~a (not an empty directory)... done\n"
+                            (get-target-path path))))
+
+                      (('file . path)
+                       (when (file-exists? (get-target-path path))
+                         ;; DO NOT remove the file if it is no longer
+                         ;; a symlink to the store, it will be backed
+                         ;; up later during create-symlinks phase.
+                         (if (symlink-to-store? (get-target-path path))
+                             (begin
+                               (format #t "Removing ~a..." (get-target-path path))
+                               (delete-file (get-target-path path))
+                               (display " done\n"))
+                             (format
+                              #t
+                              "Skipping ~a (not a symlink to store)... done\n"
+                              (get-target-path path))))))
+                    to-delete))))
+
+              (create-symlinks
+               (lambda ()
+                 (let ((to-create ((file-tree-traverse #t) new-tree)))
+                   (map
+                    (match-lambda
+                      (('dir . ".")
+                       (display
+                        "New symlinks to home-environment will be created soon.\n")
+                       (format
+                        #t "All conflicting files will go to ~a.\n\n" backup-dir))
+
+                      (('dir . path)
+                       (let ((target-path (get-target-path path)))
+                         (when (and (file-exists? target-path)
+                                    (not (directory? target-path)))
+                           (backup-file path))
+
+                         (if (file-exists? target-path)
+                             (format
+                              #t "Skipping   ~a (directory already exists)... done\n"
+                              target-path)
+                             (begin
+                               (format #t "Creating   ~a..." target-path)
+                               (mkdir target-path)
+                               (display " done\n")))))
+
+                      (('file . path)
+                       (when (file-exists? (get-target-path path))
+                         (backup-file path))
+                       (format #t "Symlinking ~a -> ~a..."
+                               (get-target-path path) (get-source-path path))
+                       (symlink (get-source-path path) (get-target-path path))
+                       (display " done\n")))
+                    to-create)))))
+
+         (when old-tree
+           (cleanup-symlinks))
+
+         (create-symlinks)
+
+         (symlink new-home new-he-path)
+         (rename-file new-he-path he-path)
+
+         (display " done\nFinished updating symlinks.\n\n")))))
+
+
+(define (update-symlinks-gexp _)
+  #~(primitive-load #$(update-symlinks-script)))
+
+(define home-symlink-manager-service-type
+  (service-type (name 'home-symlink-manager)
+                (extensions
+                 (list
+                  (service-extension
+                   home-activation-service-type
+                   update-symlinks-gexp)))
+                (default-value #f)
+                (description "Provide an @code{update-symlinks}
+script, which creates symlinks to configuration files and directories
+on every activation.  If an existing file would be overwritten by a
+symlink, backs up that file first.")))
diff --git a/gnu/home/services/utils.scm b/gnu/home/services/utils.scm
new file mode 100644
index 0000000000..cea75ee896
--- /dev/null
+++ b/gnu/home/services/utils.scm
@@ -0,0 +1,105 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services utils)
+  #:use-module (ice-9 string-fun)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+
+  #:export (maybe-object->string
+            object->snake-case-string
+            object->camel-case-string
+            list->human-readable-list))
+
+(define (maybe-object->string object)
+  "Like @code{object->string} but don't do anyting if OBJECT already is
+a string."
+  (if (string? object)
+      object
+      (object->string object)))
+
+;; Snake case: <https://en.wikipedia.org/wiki/Snake_case>
+(define* (object->snake-case-string object #:optional (style 'lower))
+  "Convert the object OBJECT to the equivalent string in ``snake
+case''.  STYLE can be three `@code{lower}', `@code{upper}', or
+`@code{capitalize}', defaults to `@code{lower}'.
+
+@example
+(object->snake-case-string 'variable-name 'upper)
+@result{} \"VARIABLE_NAME\" @end example"
+  (if (not (member style '(lower upper capitalize)))
+      (error 'invalid-style (format #f "~a is not a valid style" style))
+      (let ((stringified (maybe-object->string object)))
+        (string-replace-substring
+         (cond
+          ((equal? style 'lower) stringified)
+          ((equal? style 'upper) (string-upcase stringified))
+          (else (string-capitalize stringified)))
+         "-" "_"))))
+
+(define* (object->camel-case-string object #:optional (style 'lower))
+  "Convert the object OBJECT to the equivalent string in ``camel case''.
+STYLE can be three `@code{lower}', `@code{upper}', defaults to
+`@code{lower}'.
+
+@example
+(object->camel-case-string 'variable-name 'upper)
+@result{} \"VariableName\"
+@end example"
+  (if (not (member style '(lower upper)))
+      (error 'invalid-style (format #f "~a is not a valid style" style))
+      (let ((stringified (maybe-object->string object)))
+        (cond
+         ((eq? style 'upper)
+          (string-concatenate
+           (map string-capitalize
+                (string-split stringified (cut eqv? <> #\-)))))
+         ((eq? style 'lower)
+          (let ((splitted-string (string-split stringified (cut eqv? <> #\-))))
+            (string-concatenate
+             (cons (first splitted-string)
+                   (map string-capitalize
+                        (cdr splitted-string))))))))))
+
+(define* (list->human-readable-list lst
+                                    #:key
+                                    (cumulative? #f)
+                                    (proc identity))
+  "Turn a list LST into a sequence of terms readable by humans.
+If CUMULATIVE? is @code{#t}, use ``and'', otherwise use ``or'' before
+the last term.
+
+PROC is a procedure to apply to each of the elements of a list before
+turning them into a single human readable string.
+
+@example
+(list->human-readable-list '(1 4 9) #:cumulative? #t #:proc sqrt)
+@result{} \"1, 2, and 3\"
+@end example
+
+yields:"
+  (let* ((word (if cumulative? "and " "or "))
+         (init (append (drop-right lst 1))))
+    (format #f "~a" (string-append
+                     (string-join
+                      (map (compose maybe-object->string proc) init)
+                      ", " 'suffix)
+                     word
+                     (maybe-object->string (proc (last lst)))))))
+
diff --git a/gnu/home/services/xdg.scm b/gnu/home/services/xdg.scm
new file mode 100644
index 0000000000..4aed9a5803
--- /dev/null
+++ b/gnu/home/services/xdg.scm
@@ -0,0 +1,478 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021 Andrew Tropin <andrew@trop.in>
+;;; Copyright © 2021 Xinglu Chen <public@yoctocell.xyz>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu home services xdg)
+  #:use-module (gnu services configuration)
+  #:use-module (gnu home services configuration)
+  #:use-module (gnu home-services)
+  #:use-module (gnu packages freedesktop)
+  #:use-module (gnu home services utils)
+  #:use-module (guix gexp)
+  #:use-module (guix records)
+  #:use-module (guix i18n)
+  #:use-module (guix diagnostics)
+
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:use-module (rnrs enums)
+
+  #:export (home-xdg-base-directories-service-type
+            home-xdg-base-directories-configuration
+            home-xdg-base-directories-configuration?
+
+            home-xdg-user-directories-service-type
+            home-xdg-user-directories-configuration
+            home-xdg-user-directories-configuration?
+
+            xdg-desktop-action
+            xdg-desktop-entry
+            home-xdg-mime-applications-service-type
+            home-xdg-mime-applications-configuration))
+
+;;; Commentary:
+;;
+;; This module contains services related to XDG directories and
+;; applications.
+;;
+;; - XDG base directories
+;; - XDG user directories
+;; - XDG MIME applications
+;;
+;;; Code:
+
+
+;;;
+;;; XDG base directories.
+;;;
+
+(define (serialize-path field-name val) "")
+(define path? string?)
+
+(define-configuration home-xdg-base-directories-configuration
+  (cache-home
+   (path "$HOME/.cache")
+   "Base directory for programs to store user-specific non-essential
+(cached) data.  Files in this directory can be deleted anytime without
+loss of important data.")
+  (config-home
+   (path "$HOME/.config")
+   "Base directory for programs to store configuration files.
+Some programs store here log or state files, but it's not desired,
+this directory should contain static configurations.")
+  (data-home
+   (path "$HOME/.local/share")
+   "Base directory for programs to store architecture independent
+read-only shared data, analogus to @file{/usr/share}, but for user.")
+  (runtime-dir
+   (path "${XDG_RUNTIME_DIR:-/run/user/$UID}")
+   "Base directory for programs to store user-specific runtime files,
+like sockets.")
+  (log-home
+   (path "$HOME/.local/var/log")
+   "Base directory for programs to store log files, analogus to
+@file{/var/log}, but for user.  It is not a part of XDG Base Directory
+Specification, but helps to make implementation of home services more
+consistent.")
+  (state-home
+   (path "$HOME/.local/var/lib")
+   "Base directory for programs to store state files, like databases,
+analogus to @file{/var/lib}, but for user.  It is not a part of XDG
+Base Directory Specification, but helps to make implementation of home
+services more consistent."))
+
+(define (home-xdg-base-directories-environment-variables-service config)
+  (map
+   (lambda (field)
+     (cons (format
+            #f "XDG_~a"
+            (object->snake-case-string (configuration-field-name field) 'upper))
+           ((configuration-field-getter field) config)))
+   home-xdg-base-directories-configuration-fields))
+
+(define (ensure-xdg-base-dirs-on-activation config)
+  #~(map (lambda (xdg-base-dir-variable)
+           ((@@ (guix build utils) mkdir-p)
+            (getenv
+             xdg-base-dir-variable)))
+         '#$(map (lambda (field)
+                   (format
+                    #f "XDG_~a"
+                    (object->snake-case-string
+                     (configuration-field-name field) 'upper)))
+                 home-xdg-base-directories-configuration-fields)))
+
+(define (last-extension-or-cfg config extensions)
+  "Picks configuration value from last provided extension.  If there
+are no extensions use configuration instead."
+  (or (and (not (null? extensions)) (last extensions)) config))
+
+(define home-xdg-base-directories-service-type
+  (service-type (name 'home-xdg-base-directories)
+                (extensions
+                 (list (service-extension
+                        home-environment-variables-service-type
+                        home-xdg-base-directories-environment-variables-service)
+                       (service-extension
+                        home-activation-service-type
+                        ensure-xdg-base-dirs-on-activation)))
+                (default-value (home-xdg-base-directories-configuration))
+                (compose identity)
+                (extend last-extension-or-cfg)
+                (description "Configure XDG base directories.  This
+service introduces two additional variables @env{XDG_STATE_HOME},
+@env{XDG_LOG_HOME}.  They are not a part of XDG specification, at
+least yet, but are convinient to have, it improves the consistency
+between different home services.  The services of this service-type is
+instantiated by default, to provide non-default value, extend the
+service-type (using @code{simple-service} for example).")))
+
+(define (generate-home-xdg-base-directories-documentation)
+  (generate-documentation
+   `((home-xdg-base-directories-configuration
+      ,home-xdg-base-directories-configuration-fields))
+   'home-xdg-base-directories-configuration))
+
+
+;;;
+;;; XDG user directories.
+;;;
+
+(define (serialize-string field-name val)
+  ;; The path has to be quoted
+  (format #f "XDG_~a_DIR=\"~a\"\n"
+          (object->snake-case-string field-name 'upper) val))
+
+(define-configuration home-xdg-user-directories-configuration
+  (desktop
+   (string "$HOME/Desktop")
+   "Default ``desktop'' directory, this is what you see on your
+desktop when using a desktop environment,
+e.g. GNOME (@pxref{XWindow,,,guix.info}).")
+  (documents
+   (string "$HOME/Documents")
+   "Default directory to put documents like PDFs.")
+  (download
+   (string "$HOME/Downloads")
+   "Default directory downloaded files, this is where your Web-broser
+will put downloaded files in.")
+  (music
+   (string "$HOME/Music")
+   "Default directory for audio files.")
+  (pictures
+   (string "$HOME/Pictures")
+   "Default directory for pictures and images.")
+  (publicshare
+   (string "$HOME/Public")
+   "Default directory for shared files, which can be accessed by other
+users on local machine or via network.")
+  (templates
+   (string "$HOME/Templates")
+   "Default directory for templates.  They can be used by graphical
+file manager or other apps for creating new files with some
+pre-populated content.")
+  (videos
+   (string "$HOME/Videos")
+   "Default directory for videos."))
+
+(define (home-xdg-user-directories-files-service config)
+  `(("config/user-dirs.conf"
+     ,(mixed-text-file
+       "user-dirs.conf"
+       "enabled=False\n"))
+    ("config/user-dirs.dirs"
+     ,(mixed-text-file
+       "user-dirs.dirs"
+      (serialize-configuration
+       config
+       home-xdg-user-directories-configuration-fields)))))
+
+(define (home-xdg-user-directories-activation-service config)
+  (let ((dirs (map (lambda (field)
+                     ((configuration-field-getter field) config))
+                   home-xdg-user-directories-configuration-fields)))
+    #~(let ((ensure-dir
+             (lambda (path)
+               (mkdir-p
+                ((@@ (ice-9 string-fun) string-replace-substring)
+                 path "$HOME" (getenv "HOME"))))))
+        (display "Creating XDG user directories...")
+        (map ensure-dir '#$dirs)
+        (display " done\n"))))
+
+(define home-xdg-user-directories-service-type
+  (service-type (name 'home-xdg-user-directories)
+                (extensions
+                 (list (service-extension
+                        home-files-service-type
+                        home-xdg-user-directories-files-service)
+                       (service-extension
+                        home-activation-service-type
+                        home-xdg-user-directories-activation-service)))
+                (default-value (home-xdg-user-directories-configuration))
+                (description "Configure XDG user directories.  To
+disable a directory, point it to the $HOME.")))
+
+(define (generate-home-xdg-user-directories-documentation)
+  (generate-documentation
+   `((home-xdg-user-directories-configuration
+     ,home-xdg-user-directories-configuration-fields))
+   'home-xdg-user-directories-configuration))
+
+
+;;;
+;;; XDG MIME applications.
+;;;
+
+;; Example config
+;;
+;;  (home-xdg-mime-applications-configuration
+;;   (added '((x-scheme-handler/magnet . torrent.desktop)))
+;;   (default '((inode/directory . file.desktop)))
+;;   (removed '((inode/directory . thunar.desktop)))
+;;   (desktop-entries
+;;    (list (xdg-desktop-entry
+;;           (file "file")
+;;           (name "File manager")
+;;           (type 'application)
+;;           (config
+;;            '((exec . "emacsclient -c -a emacs %u"))))
+;;          (xdg-desktop-entry
+;;           (file "text")
+;;           (name "Text editor")
+;;           (type 'application)
+;;           (config
+;;            '((exec . "emacsclient -c -a emacs %u")))
+;;           (actions
+;;            (list (xdg-desktop-action
+;;                   (action 'create)
+;;                   (name "Create an action")
+;;                   (config
+;;                    '((exec . "echo hi"))))))))))
+
+;; See
+;; <https://specifications.freedesktop.org/shared-mime-info-spec/shared-mime-info-spec-latest.html>
+;; <https://specifications.freedesktop.org/mime-apps-spec/mime-apps-spec-latest.html>
+
+(define (serialize-alist field-name val)
+  (define (serialize-mimelist-entry key val)
+    (let ((val (cond
+                ((list? val)
+                 (string-join (map maybe-object->string val) ";"))
+                ((or (string? val) (symbol? val))
+                 val)
+                (else (raise (formatted-message
+                              (G_ "\
+The value of an XDG MIME entry must be a list, string or symbol, was given ~a")
+                              val))))))
+      (format #f "~a=~a\n" key val)))
+
+  (define (merge-duplicates alist acc)
+    "Merge values that have the same key.
+
+@example
+(merge-duplicates '((key1 . value1)
+                    (key2 . value2)
+                    (key1 . value3)
+                    (key1 . value4)) '())
+
+@result{} ((key1 . (value4 value3 value1)) (key2 . value2))
+@end example"
+    (cond
+     ((null? alist) acc)
+     (else (let* ((head (first alist))
+                  (tail (cdr alist))
+                  (key (first head))
+                  (value (cdr head))
+                  (duplicate? (assoc key acc))
+                  (ensure-list (lambda (x)
+                                 (if (list? x) x (list x)))))
+             (if duplicate?
+                 ;; XXX: This will change the order of things,
+                 ;; though, it shouldn't be a problem for XDG MIME.
+                 (merge-duplicates
+                  tail
+                  (alist-cons key
+                              (cons value (ensure-list (cdr duplicate?)))
+                              (alist-delete key acc)))
+                 (merge-duplicates tail (cons head acc)))))))
+
+  (string-append (if (equal? field-name 'default)
+                     "\n[Default Applications]\n"
+                     (format #f "\n[~a Associations]\n"
+                             (string-capitalize (symbol->string field-name))))
+                 (generic-serialize-alist string-append
+                                          serialize-mimelist-entry
+                                          (merge-duplicates val '()))))
+
+(define xdg-desktop-types (make-enumeration
+                           '(application
+                             link
+                             directory)))
+
+(define (xdg-desktop-type? type)
+  (unless (enum-set-member? type xdg-desktop-types)
+    (raise (formatted-message
+            (G_ "XDG desktop type must be of of ~a, was given: ~a")
+            (list->human-readable-list (enum-set->list xdg-desktop-types))
+            type))))
+
+;; TODO: Add proper docs for this
+;; XXX: 'define-configuration' require that fields have a default
+;; value.
+(define-record-type* <xdg-desktop-action>
+  xdg-desktop-action make-xdg-desktop-action
+  xdg-desktop-action?
+  (action xdg-desktop-action-action)  ; symbol
+  (name   xdg-desktop-action-name)    ; string
+  (config xdg-desktop-action-config   ; alist
+          (default '())))
+
+(define-record-type* <xdg-desktop-entry>
+  xdg-desktop-entry make-xdg-desktop-entry
+  xdg-desktop-entry?
+  ;; ".desktop" will automatically be added
+  (file    xdg-desktop-entry-file)    ; string
+  (name    xdg-desktop-entry-name)    ; string
+  (type    xdg-desktop-entry-type)    ; xdg-desktop-type
+  (config  xdg-desktop-entry-config   ; alist
+           (default '()))
+  (actions xdg-desktop-entry-actions  ; list of <xdg-desktop-action>
+           (default '())))
+
+(define desktop-entries? (list-of xdg-desktop-entry?))
+(define (serialize-desktop-entries field-name val) "")
+
+(define (serialize-xdg-desktop-entry entry)
+  "Return a tuple of the file name for ENTRY and the serialized
+configuration."
+  (define (format-config key val)
+    (let ((val (cond
+                ((list? val)
+                 (string-join (map maybe-object->string val) ";"))
+                ((boolean? val)
+                 (if val "true" "false"))
+                (else val)))
+          (key (string-capitalize (maybe-object->string key))))
+      (list (if (string-suffix? key "?")
+                (string-drop-right key (- (string-length key) 1))
+                key)
+            "=" val "\n")))
+
+  (define (serialize-alist config)
+    (generic-serialize-alist identity format-config config))
+
+  (define (serialize-xdg-desktop-action action)
+    (match action
+      (($ <xdg-desktop-action> action name config)
+       `(,(format #f "[Desktop Action ~a]\n"
+                  (string-capitalize (maybe-object->string action)))
+         ,(format #f "Name=~a\n" name)
+         ,@(serialize-alist config)))))
+
+  (match entry
+    (($ <xdg-desktop-entry> file name type config actions)
+     (list (if (string-suffix? file ".desktop")
+               file
+               (string-append file ".desktop"))
+           `("[Desktop Entry]\n"
+             ,(format #f "Name=~a\n" name)
+             ,(format #f "Type=~a\n"
+                      (string-capitalize (symbol->string type)))
+             ,@(serialize-alist config)
+             ,@(append-map serialize-xdg-desktop-action actions))))))
+
+(define-configuration home-xdg-mime-applications-configuration
+  (added
+   (alist '())
+   "An association list of MIME types and desktop entries which indicate
+that the application should used to open the specified MIME type.  The
+value has to be string, symbol, or list of strings or symbols, this
+applies to the `@code{default}', and `@code{removed}' fields as well.")
+  (default
+    (alist '())
+    "An association list of MIME types and desktop entries which indicate
+that the application should be the default for opening the specified
+MIME type.")
+  (removed
+   (alist '())
+   "An association list of MIME types and desktop entries which indicate
+that the application cannot open the specified MIME type.")
+  (desktop-entries
+   (desktop-entries '())
+   "A list of XDG desktop entries to create.  See
+@code{xdg-desktop-entry}."))
+
+(define (home-xdg-mime-applications-files-service config)
+  (define (add-xdg-desktop-entry-file entry)
+    (let ((file (first entry))
+          (config (second entry)))
+      (list (format #f "local/share/applications/~a" file)
+          (apply mixed-text-file
+                 (format #f "xdg-desktop-~a-entry" file)
+                 config))))
+
+  (append
+   `(("config/mimeapps.list"
+      ,(mixed-text-file
+        "xdg-mime-appplications"
+        (serialize-configuration
+         config
+         home-xdg-mime-applications-configuration-fields))))
+   (map (compose add-xdg-desktop-entry-file serialize-xdg-desktop-entry)
+        (home-xdg-mime-applications-configuration-desktop-entries config))))
+
+(define (home-xdg-mime-applications-extension old-config extension-configs)
+  (define (extract-fields config)
+    ;; return '(added default removed desktop-entries)
+    (list (home-xdg-mime-applications-configuration-added config)
+          (home-xdg-mime-applications-configuration-default config)
+          (home-xdg-mime-applications-configuration-removed config)
+          (home-xdg-mime-applications-configuration-desktop-entries config)))
+
+  (define (append-configs elem acc)
+    (list (append (first elem) (first acc))
+          (append (second elem) (second acc))
+          (append (third elem) (third acc))
+          (append (fourth elem) (fourth acc))))
+
+  ;; TODO: Implement procedure to check for duplicates without
+  ;; sacrificing performance.
+  ;;
+  ;; Combine all the alists from 'added', 'default' and 'removed'
+  ;; into one big alist.
+  (let ((folded-configs (fold append-configs
+                              (extract-fields old-config)
+                              (map extract-fields extension-configs))))
+    (home-xdg-mime-applications-configuration
+     (added (first folded-configs))
+     (default (second folded-configs))
+     (removed (third folded-configs))
+     (desktop-entries (fourth folded-configs)))))
+
+(define home-xdg-mime-applications-service-type
+  (service-type (name 'home-xdg-mime-applications)
+                (extensions
+                 (list (service-extension
+                        home-files-service-type
+                        home-xdg-mime-applications-files-service)))
+                (compose identity)
+                (extend home-xdg-mime-applications-extension)
+                (default-value (home-xdg-mime-applications-configuration))
+                (description
+                 "Configure XDG MIME applications, and XDG desktop entries.")))