cups-service

[Danny Milosavljevic <dannym@scratchpost.org>]

I added a cups-service to actually enable printing eventually, see below.

What it should do (and doesn't do yet) is union together several directories of other packages.

The generated cups-files.conf should contain as "DataDir" (usually /usr/share) the data directory that cupsd should use, which should contain all those merged-together configs (as subdirs), and as "ServerBin" (usually /usr/lib/cups) the actual executables. It is possible to pass the location of cups-files.conf when starting up cupsd. 

The subdirs in datadir are especially:

- drv/ for the driver infos. These contain ppd basenames, among lots of other things. These are a variable number of files, but flat hierarchy.
- mime/ for mime types. These are a constant number of files (flat dir hierarchy), to be concatenated each.

The PPDs are kinda difficult. A possibility is to put them into the directory specified as "ServerRoot" (usually /etc/cups) as subdir "ppd" but I think that's supposed to be for user customizations. Cups ppds are usually in /usr/share/ppd . Cupsfilters ppds are usually in /usr/share/ppd/cupsfilters . hplip ppds are usually in /usr/share/hplip (not yet sure how they get there in the first place, though). cups-driverd get_file actually hard-codes /usr/share/ppd sometimes but usually uses (string-append DataDir subdir name) - but my Debian installation has none of the latter.

The subdirs in serverbin are:

- backend/ (flat dir hierarchy). Overwhelmingly ELF; one Python (what version?) script.
- filter/ (flat dir hierarchy). Overwhelmingly ELF; a few Python (what version?) scripts, one shell script.
- driver/ for the actual drivers (flat dir hierarchy). Most of those (all but 1) are python3 scripts. One ELF.

How do I find out where the cupsd executable is / ensure that it's actually there?

Sources to be merged should be the packages:
- cups-filters
- cups
- hplip
- eventually foomatic

diff --git a/gnu/services/printing.scm b/gnu/services/printing.scm
new file mode 100644
index 0000000..4bc33a2
--- /dev/null
+++ b/gnu/services/printing.scm
@@ -0,0 +1,109 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015 Mark H Weaver <mhw@netris.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 the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu services printing)
+  #:use-module (gnu services)
+  #:use-module (gnu services shepherd)
+  #:use-module (gnu packages cups)
+  #:use-module (guix gexp)
+  #:use-module (guix records)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-26)
+  #:use-module (ice-9 match)
+  #:export (cups-service))
+
+; TODO or just fetch the one from cups and modify it a bit.
+(define (default-cups-files-config data-dir)
+  ;; generate cups-files.conf [for cupsd -s ...], especially dynamically set DataDir.
+  (mixed-text-file "cups-files.conf"
+                   "AccessLog syslog\n"
+                   "ErrorLog syslog\n"
+                   "PageLog syslog\n"
+                   "FatalErrors all\n"
+                   "SyncOnClose Yes\n"
+                   "User nobody\n"
+                   "Group lp\n"
+                   ; FIXME SystemGroup lpadmin sys system root
+                   ; FIXME ConfigFilePerm
+                   ;; DataDir /var/lib/cupsd/data
+                   (string-append "DataDir " data-dir "\n") ; /gnu/store/1h53jmsx7gm7b2sfk0h0k6bgmp8fhv0i-cups-2.1.0/share/cups
+                   (string-append "DocumentRoot" /gnu/store/1h53jmsx7gm7b2sfk0h0k6bgmp8fhv0i-cups-2.1.0 "/share/doc/cups\n")
+                   "CacheDir /var/cache/cups\n"
+                   "StateDir /var/run/cups\n"
+                   ; FIXME FontPath /zzz
+                   "Printcap /etc/printcap\n"
+                   "PrintcapFormat bsd\n"
+                   "RequestRoot /var/spool/cups\n"
+                   ;;/gnu/store/1h53jmsx7gm7b2sfk0h0k6bgmp8fhv0i-cups-2.1.0/lib/cups
+                   "ServerBin /home/dannym/.guix-profile/lib/cups\n" ; FIXME
+                   "ServerRoot /etc/cups\n" ; FIXME
+))
+
+(define-record-type* <cups>
+  cups make-cups
+  cups?
+  (printers cups-printers)
+  (provision cups-provision))
+
+; TODO cupsd -c /etc/cupsd.conf -s /etc/cups-files.conf -f
+; TODO what user should cupsd run as? (Debian: root)
+; TODO cups-browsed (Debian: also as root)
+; TODO list of printers; paper size, printer vendor and model, interface (if necessary).
+; TODO binding to network interface; running the config html page; auth there; auth in general?
+; TODO support scanners and hpaio thing as sane dll
+
+; FIXME extensions (list (service-extension ...
+; FIXME compose concatenate
+; FIXME extend (lambda (config actions)
+; merge: /var/lib/hp ? no.
+; merge: /etc/hp ? no.
+; merge: /usr/share/hal/fdi ? useless.
+; merge: /etc/udev/rules.d ? done.
+; merge: /lib/systemd/system ? useless.
+; TODO merge: /lib/cups/filter
+; TODO merge: /lib/cups/backend
+; TODO merge: mime.types
+; TODO merge: /share/applications
+; TODO merge: /usr/share/ppd/HP via DRV?
+; TODO merge: drv into DataDir
+
+(define cups-service-type
+  (shepherd-service-type
+   'cups
+   (match-lambda
+     (($ <cups> printers provision)
+      (let ((loopback? (memq 'loopback provision)))
+        (shepherd-service
+         (requirement '(udev networking)) ; TODO check actual config and reduce
+         (documentation "Bring up printing services.")
+         (provision provision)
+         (start #~(make-forkexec-constructor
+                   (list (string-append "/sbin/cupsd") ; FIXME #$cups
+                         "-s" (default-cups-files-config "/tmp") ; FIXME pass merged datadir
+                         ; FIXME "-c" cups config
+                         "-f")))
+         (stop #~(make-kill-destructor))))))))
+
+(define* (cups-service #:key printers (provision '(printing)) )
+  "Return a printing service that starts cups."
+  (service cups-service-type
+           (cups (printers printers)
+                 (provision provision))))
+