services: Add rottlog.

* gnu/services/admin.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Log Rotation): New node.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

doc/guix.texi

@@ -26,7 +26,8 @@ Copyright @copyright{} 2016 Ben Woodcroft@*
 Copyright @copyright{} 2016 Chris Marusich@*
 Copyright @copyright{} 2016 Efraim Flashner@*
 Copyright @copyright{} 2016 John Darrington@*
-Copyright @copyright{} 2016 ng0
+Copyright @copyright{} 2016 ng0@*
+Copyright @copyright{} 2016 Jan Nieuwenhuizen
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -213,6 +214,7 @@ Services
 
 * Base Services::               Essential system services.
 * Scheduled Job Execution::     The mcron service.
+* Log Rotation::                The rottlog service.
 * Networking Services::         Network setup, SSH daemon, etc.
 * X Window::                    Graphical display.
 * Desktop Services::            D-Bus and desktop services.
@@ -7581,6 +7583,7 @@ declaration.
 @menu
 * Base Services::               Essential system services.
 * Scheduled Job Execution::     The mcron service.
+* Log Rotation::                The rottlog service.
 * Networking Services::         Network setup, SSH daemon, etc.
 * X Window::                    Graphical display.
 * Desktop Services::            D-Bus and desktop services.
@@ -8055,6 +8058,85 @@ specifications,, mcron, GNU@tie{}mcron}).
 @end deftp
 
 
+@node Log Rotation
+@subsubsection Log Rotation
+
+@cindex rottlog
+@cindex log rotation
+Log files such as those found in @file{/var/log} tend to grow endlessly,
+so it's a good idea to @dfn{rotate} them once in a while---i.e., archive
+their contents in separate files, possibly compressed.  The @code{(gnu
+services admin)} module provides an interface to GNU@tie{}Rot[t]log, a
+log rotation tool (@pxref{Top,,, rottlog, GNU Rot[t]log Manual}).
+
+The example below defines an operating system that provides log rotation
+with the default settings.
+
+@lisp
+(use-modules (guix) (gnu))
+(use-service-modules admin mcron)
+(use-package-modules base idutils)
+
+(operating-system
+  ;; @dots{}
+  (services (cons* (mcron-service)
+                   (service rottlog-service-type (rottlog-configuration)) 
+                   %base-services)))
+@end lisp
+
+@defvr {Scheme Variable} rottlog-service-type
+This is the type of the Rottlog service, whose value is a
+@code{rottlog-configuration} object.
+
+This service type can define mcron jobs (@pxref{Scheduled Job
+Execution}) to run the rottlog service.
+@end defvr
+
+@deftp {Data Type} rottlog-configuration
+Data type representing the configuration of rottlog.
+
+@table @asis
+@item @code{rottlog} (default: @code{rottlog})
+The Rottlog package to use.
+
+@item @code{rc-file} (default: @code{(file-append rottlog "/etc/rc")})
+The Rottlog configuration file to use (@pxref{Mandatory RC Variables,,,
+rottlog, GNU Rot[t]log Manual}).
+
+@item @code{periodic-rotations} (default: @code{`(("weekly" %default-rotatations))})
+A list of Rottlog period-name/period-config tuples.
+
+For example, taking an example from the Rottlog manual (@pxref{Period
+Related File Examples,,, rottlog, GNU Rot[t]log Manual}), a valid tuple
+might be:
+
+@example
+("daily" ,(plain-file "daily"
+                      "\
+     /var/log/apache/* @{
+        storedir apache-archives
+        rotate 6
+        notifempty
+        nocompress
+     @}"))
+@end example
+
+@item @code{jobs}
+This is a list of gexps where each gexp corresponds to an mcron job
+specification (@pxref{Scheduled Job Execution}).
+@end table
+@end deftp
+
+@defvr {Scheme Variable} %default-rotations
+Specifies weekly rotation of @var{%rotated-files} and
+@code{"/var/log/shepherd.log"}.
+@end defvr
+
+@defvr {Scheme Variable} %rotated-files
+The list of syslog-controlled files to be rotated.  By default it is:
+@code{'("/var/log/messages" "/var/log/secure")}.
+@end defvr
+
 @node Networking Services
 @subsubsection Networking Services
 

gnu/local.mk

@@ -385,6 +385,7 @@ GNU_SYSTEM_MODULES =				\
   %D%/packages/zip.scm				\
 						\
   %D%/services.scm				\
+  %D%/services/admin.scm			\
   %D%/services/avahi.scm			\
   %D%/services/base.scm				\
   %D%/services/databases.scm			\

gnu/services/admin.scm

@@ -0,0 +1,117 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
+;;;
+;;; 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 thye GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu services admin)
+  #:use-module (gnu packages admin)
+  #:use-module (gnu packages base)
+  #:use-module (gnu services)
+  #:use-module (gnu services mcron)
+  #:use-module (gnu services shepherd)
+  #:use-module (guix gexp)
+  #:use-module (guix packages)
+  #:use-module (guix records)
+  #:use-module (srfi srfi-1)
+  #:export (%default-rotations
+            %rotated-files
+            rottlog-configuration
+            rottlog-configuration?
+            rottlog-service
+            rottlog-service-type))
+
+;;; Commentary:
+;;;
+;;; This module implements configuration of rottlog by writing
+;;; /etc/rottlog/{rc,hourly|daily|weekly}.  Example usage
+;;;
+;;;     (mcron-service)
+;;;     (service rottlog-service-type (rottlog-configuration))
+;;;
+;;; Code:
+
+(define %rotated-files
+  '("/var/log/messages" "/var/log/secure"))
+
+(define (syslog-rotation-config file)
+  #~(#$file " {
+        sharedscripts
+        postrotate
+        " #$coreutils "/bin/kill -HUP $(cat /var/run/syslog.pid) 2> /dev/null
+        endscript
+}
+"))
+
+(define (simple-rotation-config file)
+  (string-append file " {
+        sharedscripts
+        postrotate
+        endscript
+}
+"))
+
+(define %default-rotations
+  `(("weekly"
+     ,(computed-file "rottlog.weekly"
+                     #~(call-with-output-file #$output
+                         (lambda (port)
+                           (display
+                            (string-join
+                             (apply append '#$(map syslog-rotation-config
+                                                   %rotated-files))
+                             "")
+                            port)
+                           (display #$(simple-rotation-config
+                                       "/var/log/shepherd.log")
+                                    port)))))))
+
+(define (default-jobs rottlog)
+  (list #~(job '(next-hour '(0))                  ;midnight
+               (lambda ()
+                 (system* #$(file-append rottlog "/sbin/rottlog"))))
+        #~(job '(next-hour '(12))                 ;noon
+               (lambda ()
+                 (system* #$(file-append rottlog "/sbin/rottlog"))))))
+
+(define-record-type* <rottlog-configuration>
+  rottlog-configuration make-rottlog-configuration
+  rottlog-configuration?
+  (rottlog            rottlog-rottlog             ;package
+                      (default rottlog))
+  (rc-file            rottlog-rc-file             ;file-like
+                      (default (file-append rottlog "/etc/rc")))
+  (periodic-rotations rottlog-periodic-rotations  ;list of (name file) tuples
+                      (default %default-rotations))
+  (jobs               rottlog-jobs                ;list of <mcron-job>
+                      (default #f)))
+
+(define (rottlog-etc config)
+  `(("rottlog" ,(file-union "rottlog"
+                            (cons `("rc" ,(rottlog-rc-file config))
+                                  (rottlog-periodic-rotations config))))))
+
+(define (rottlog-jobs-or-default config)
+  (or (rottlog-jobs config)
+      (default-jobs (rottlog-rottlog config))))
+
+(define rottlog-service-type
+  (service-type
+   (name 'rottlog)
+   (extensions (list (service-extension etc-service-type rottlog-etc)
+                     (service-extension mcron-service-type
+                                        rottlog-jobs-or-default)))))
+
+;;; admin.scm ends here