On Thu, 03 Aug 2017 19:20:08 +0300
Oleg Pykhalov <go.wigust@gmail.com> wrote:

> From 1ca5dab9f0a05205a85cc78d9a099bbe991ce884 Mon Sep 17 00:00:00 2001
> From: Oleg Pykhalov <go.wigust@gmail.com>
> Date: Thu, 27 Jul 2017 04:01:01 +0300
> Subject: [PATCH] gnu: Add rsync service.
> 
> * doc/guix.texi (Incremental file transfer): Add documentation.
> * gnu/services/rsync.scm (<rsync-configuration>): New record type.
> (rsync-accounts, rsync-shepherd-service): New service extensions.
> (rsync-service-type): New service type.
> ---
>  doc/guix.texi          |  67 +++++++++++++++++++++++
>  gnu/local.mk           |   1 +
>  gnu/services/rsync.scm | 140
> +++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed,
> 208 insertions(+) create mode 100644 gnu/services/rsync.scm

I've got as far as successfully trying this out in a VM now. I had to
make one change that I'll note below.

> diff --git a/doc/guix.texi b/doc/guix.texi
> index cda131557..cb5b59615 100644
> --- a/doc/guix.texi
> +++ b/doc/guix.texi
> @@ -16528,6 +16528,73 @@ Extra options will be passed to @code{git
> daemon}, please run @end table
>  @end deftp
>  
> +@subsubsection File transfer
> +
> +The @code{(gnu services rsync)} module provides the following
> services: +
> +@subsubheading Rsync service
> +
> +You might want an rsync daemon if you have files that you want
> available +so anyone (or just yourself) can download existing files
> or upload new +files.
> +
> +@deffn {Scheme Variable} rsync-service-type
> +This is the type for the @uref{https://rsync.samba.org} rsync daemon,
> +@command{rsync-configuration} record as in this example:
> +
> +@example
> +(service rsync-service-type
> +         (rsync-configuration))
> +@end example
> +
> +See below for details about @code{rsync-configuration}.
> +@end deffn
> +
> +@deftp {Data Type} rsync-configuration
> +Data type representing the configuration for @code{rsync-service}.
> +
> +@table @asis
> +@item @code{package} (default: @var{rsync})
> +@code{rsync} package to use.
> +
> +@item @code{port-number} (default: @code{873})
> +TCP port on which @command{rsync} listens for incoming connections.
> If +port is less than @code{1024} @command{rsync} will be started as
> the +@code{root} user and group.
> +
> +@item @code{pid-file} (default: @code{"/var/run/rsyncd.pid"})
> +Name of the file where @command{rsync} writes its PID.
> +
> +@item @code{lock-file} (default: @code{"/var/run/rsyncd.lock"})
> +Name of the file where @command{rsync} writes its lock file.
> +
> +@item @code{log-file} (default: @code{"/var/log/rsyncd.log"})
> +Name of the file where @command{rsync} writes its log file.
> +
> +@item @code{use-choot?} (default: @var{#f})
> +Whether to use chroot for @command{rsync} shared directory.
> +
> +@item @code{share-path} (default: @file{/srv/rsync})
> +Location of the @command{rsync} shared directory.
> +
> +@item @code{share-comment} (default: @code{"Rsync share"})
> +Comment of the @command{rsync} shared directory.
> +
> +@item @code{read-only?} (default: @var{#f})
> +Read-write permissions to shared directory.
> +
> +@item @code{timeout} (default: @code{300})
> +I/O timeout in seconds.
> +
> +@item @code{user} (default: @code{"rsyncd"})
> +Privilege separation user.
> +
> +@item @code{group} (default: @code{"rsyncd"})
> +Privilege separation group.
> +
> +@end table
> +@end deftp
> +
>  @node Setuid Programs
>  @subsection Setuid Programs
>  
> diff --git a/gnu/local.mk b/gnu/local.mk
> index f48e6638b..bc445b731 100644
> --- a/gnu/local.mk
> +++ b/gnu/local.mk
> @@ -445,6 +445,7 @@ GNU_SYSTEM_MODULES
> =				\
> %D%/services/shepherd.scm			\
> %D%/services/herd.scm				\
> %D%/services/pm.scm				\
> +  %D%/services/rsync.scm			\
>    %D%/services/sddm.scm				\
>    %D%/services/spice.scm				\
>    %D%/services/ssh.scm				\
> diff --git a/gnu/services/rsync.scm b/gnu/services/rsync.scm
> new file mode 100644
> index 000000000..b5ba68291
> --- /dev/null
> +++ b/gnu/services/rsync.scm
> @@ -0,0 +1,140 @@
> +;;; GNU Guix --- Functional package management for GNU
> +;;; Copyright © 2017 Oleg Pykhalov <go.wigust@gmail.com>
> +;;;
> +;;; 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 services rsync)
> +  #:use-module (gnu services)
> +  #:use-module (gnu services base)
> +  #:use-module (gnu services shepherd)
> +  #:use-module (gnu system shadow)
> +  #:use-module (gnu packages rsync)
> +  #:use-module (gnu packages admin)
> +  #:use-module (guix records)
> +  #:use-module (guix gexp)
> +  #:use-module (srfi srfi-1)
> +  #:use-module (srfi srfi-26)
> +  #:use-module (ice-9 match)
> +  #:export (rsync-configuration
> +            rsync-configuration?
> +            rsync-service-type))
> +
> +;;;; Commentary:
> +;;;
> +;;; This module implements a service that to run instance of Rsync,
> +;;; files synchronization tool.
> +;;;
> +;;;; Code:
> +
> +(define-record-type* <rsync-configuration>
> +  rsync-configuration make-rsync-configuration
> +  rsync-configuration?
> +  (package       rsync-configuration-package ;package
> +                 (default rsync))
> +  (port-number   rsync-configuration-port-number ;integer
> +                 (default 873))
> +  (pid-file      rsync-configuration-pid-file ;string
> +                 (default "/var/run/rsyncd.pid"))
> +  (lock-file     rsync-configuration-lock-file ;string
> +                 (default "/var/run/rsyncd.lock"))
> +  (log-file      rsync-configuration-log-file ;string
> +                 (default "/var/log/rsyncd.log"))
> +  (use-chroot?   rsync-configuration-use-chroot? ;boolean
> +                 (default #f))
> +  (share-path    rsync-configuration-share-path ;string
> +                 (default "/srv/rsync"))
> +  (share-comment rsync-configuration-share-comment ;string
> +                 (default "Rsync share"))
> +  (read-only?    rsync-configuration-read-only? ;boolean
> +                 (default #f))
> +  (timeout       rsync-configuration-timeout ;integer
> +                 (default 300))
> +  (user          rsync-configuration-user ;string
> +                 (default "rsyncd"))
> +  (group         rsync-configuration-group ;string
> +                 (default "rsyncd")))
> +
> +(define (rsync-account config)
> +  "Return the user accounts and user groups for CONFIG."
> +  (let ((rsync-user (rsync-configuration-user config))
> +        (rsync-group (rsync-configuration-group config)))
> +    (list (user-group (name "rsyncd") (system? #t))
> +          (user-account
> +           (name rsync-user)
> +           (system? #t)
> +           (group rsync-group)
> +           (comment "rsyncd privilege separation user")
> +           (home-directory "/var/run/rsyncd")
> +           (shell #~(string-append #$shadow "/sbin/nologin"))))))
> +
> +(define (rsync-activation config)
> +  "Return the activation GEXP for CONFIG."
> +  #~(begin
> +      (use-modules (guix build utils))
> +      (let ((share-path #$(rsync-configuration-share-path config))
> +            (user (getpw #$(rsync-configuration-user config)))
> +            (group (getpw #$(rsync-configuration-group config))))
> +        (and=> share-path mkdir-p)
> +        (chown share-path
> +               (passwd:uid user)
> +               (group:gid group)))))
> +
> +(define (rsync-config-file config)
> +  "Return the rsync configuration file corresponding to CONFIG."
> +  (match config
> +    (($ <rsync-configuration> package port-number pid-file
> +                              lock-file log-file use-chroot?
> share-path
> +                              share-comment read-only? timeout user
> group)
> +     (mixed-text-file "rsync.conf"
> +                      "pid file = " pid-file "\n"
> +                      "lock file = " lock-file "\n"
> +                      "log file = " log-file "\n"
> +                      "port = " (number->string port-number) "\n"
> +                      "use chroot = " (if use-chroot? "true"
> "false") "\n"

I needed to add "uid = " user "\n" here, otherwise I got permission
issues when copying files to the share.

> +                      "gid = " group "\n"
> +                      "[files]\n"
> +                      "path = " share-path "\n"
> +                      "comment = " share-comment "\n"
> +                      "read only = " (if read-only? "true" "false")
> "\n"
> +                      "timeout = " (number->string timeout) "\n"))))
> +
> +(define (rsync-shepherd-service config)
> +  "Return a <shepherd-service> for rsync with CONFIG."
> +  (let* ((rsync (rsync-configuration-package config))
> +         (pid-file (rsync-configuration-pid-file config))
> +         (port (rsync-configuration-port-number config))
> +         (user (if (> port  1024) (rsync-configuration-user config)
> "root"))
> +         (group (if (> port  1024) (rsync-configuration-group
> config) "root")))
> +    (list (shepherd-service
> +           (provision '(rsync))
> +           (documentation "Run rsync daemon.")
> +           (start #~(make-forkexec-constructor
> +                     (list (string-append #$rsync "/bin/rsync")
> +                           "--config" #$(rsync-config-file config)
> +                           "--daemon")
> +                     #:pid-file #$pid-file
> +                     #:user #$user
> +                     #:group #$group))
> +           (stop #~(make-kill-destructor))))))
> +
> +(define rsync-service-type
> +  (service-type
> +   (name 'rsync)
> +   (extensions
> +    (list (service-extension shepherd-root-service-type
> rsync-shepherd-service)
> +          (service-extension account-service-type rsync-account)
> +          (service-extension activation-service-type
> rsync-activation)))
> +   (default-value (rsync-configuration))))

I've attached the beginnings of a system test for this. I haven't got
as far as actually testing the service directly yet, but I'm going to
try testing it, both when running as root, and when not running as
root.

A VM start script can be created from this rsync.scm file, by running:
  guix system vm gnu/tests/rsync.scm

Also, the test itself can be run by doing:
  make check-system TESTS=rsync