From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38649) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dFpBP-0001SI-QJ for guix-patches@gnu.org; Tue, 30 May 2017 18:00:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dFpBL-0008NQ-0E for guix-patches@gnu.org; Tue, 30 May 2017 18:00:07 -0400 Received: from debbugs.gnu.org ([208.118.235.43]:43205) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dFpBK-0008NM-Tt for guix-patches@gnu.org; Tue, 30 May 2017 18:00:02 -0400 Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1dFpBK-00022P-JJ for guix-patches@gnu.org; Tue, 30 May 2017 18:00:02 -0400 Subject: bug#27155: [PATCH 0/2] Support service extensions on the "final" service values Resent-Message-ID: Received: from eggs.gnu.org ([2001:4830:134:3::10]:38518) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dFpAp-0001QN-1n for guix-patches@gnu.org; Tue, 30 May 2017 17:59:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dFpAo-0008JD-5H for guix-patches@gnu.org; Tue, 30 May 2017 17:59:31 -0400 From: Ludovic =?UTF-8?Q?Court=C3=A8s?= Date: Tue, 30 May 2017 23:58:50 +0200 Message-Id: <20170530215850.7522-1-ludo@gnu.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-patches-bounces+kyle=kyleam.com@gnu.org Sender: "Guix-patches" To: 27155@debbugs.gnu.org Cc: Alex Kost Hello! This patch adds support for service extensions that modify the "final" values of a service. This is meant to implement cross-cutting concerns as well as system-wide customization as discussed with Alex long ago: https://lists.gnu.org/archive/html/guix-devel/2015-11/msg00623.html https://lists.gnu.org/archive/html/guix-devel/2016-09/msg01505.html To summarize, a "finalization extension" (for lack of a better name) gets the final value of a service and returns a new value for that service. This is in contrast with a "normal" extension which can only contribute to the value of a target service, and not inspect the value of that target service. For example, for the /etc service, a "normal" extension can only add entries for /etc. A "finalization" extension can instead inspect and change all the /etc entries. IOW, it is a sort of a "sudo" for service extensions; it's also quite inelegant compared to the "normal" extension mechanism, but it's certainly useful. A use case is given in the second patch: we change all the PAM services to use pam_elogind.so or pam_limits.so. Likewise, the 'rename-etc-files' service below shows how to rename all the files in /etc (for illustration purposes only :-)): (define rename-etc-files (let ((rename (lambda (prefix entries) (map (match-lambda ((name . rest) (cons (string-append prefix name) rest))) entries)))) (service-type (name 'rename-etc-files) (extensions (list (service-extension etc-service-type (const '()) rename)))))) (operating-system ;; ... (services (cons* (service rename-etc-files "foo-") ...))) I think this should fulfill the need that Alex had expressed, which is to not only be able to add files to /etc, but also to have the ability to inspect and modify what goes to /etc. The first patch currently lacks doc. I'll work on it if there's consensus on the approach. Feedback welcome! Ludo'. Ludovic Courtès (2): DRAFT services: Extensions can specify a "finalization" procedure. system: pam: Remove custom API to transform PAM services. gnu/services.scm | 52 ++++++++++++++++++++++++++++++++++++++---------- gnu/services/base.scm | 33 ++++++++++++++++-------------- gnu/services/desktop.scm | 23 +++++++++++---------- gnu/system/pam.scm | 44 ++++++++-------------------------------- tests/services.scm | 34 +++++++++++++++++++++++++++++++ 5 files changed, 114 insertions(+), 72 deletions(-) -- 2.13.0