gnu/system/mapped-devices.scm

   1 ;;; GNU Guix --- Functional package management for GNU
   2 ;;; Copyright © 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
   3 ;;; Copyright © 2016 Andreas Enge <andreas@enge.fr>
   4 ;;;
   5 ;;; This file is part of GNU Guix.
   6 ;;;
   7 ;;; GNU Guix is free software; you can redistribute it and/or modify it
   8 ;;; under the terms of the GNU General Public License as published by
   9 ;;; the Free Software Foundation; either version 3 of the License, or (at
  10 ;;; your option) any later version.
  11 ;;;
  12 ;;; GNU Guix is distributed in the hope that it will be useful, but
  13 ;;; WITHOUT ANY WARRANTY; without even the implied warranty of
  14 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 ;;; GNU General Public License for more details.
  16 ;;;
  17 ;;; You should have received a copy of the GNU General Public License
  18 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
  19
  20 (define-module (gnu system mapped-devices)
  21   #:use-module (guix gexp)
  22   #:use-module (guix records)
  23   #:use-module (guix modules)
  24   #:use-module (gnu services)
  25   #:use-module (gnu services shepherd)
  26   #:autoload   (gnu packages cryptsetup) (cryptsetup-static)
  27   #:autoload   (gnu packages linux) (mdadm-static)
  28   #:use-module (srfi srfi-1)
  29   #:use-module (ice-9 match)
  30   #:export (mapped-device
  31             mapped-device?
  32             mapped-device-source
  33             mapped-device-target
  34             mapped-device-type
  35
  36             mapped-device-kind
  37             mapped-device-kind?
  38             mapped-device-kind-open
  39             mapped-device-kind-close
  40
  41             device-mapping-service-type
  42             device-mapping-service
  43
  44             luks-device-mapping
  45             raid-device-mapping))
  46
  47 ;;; Commentary:
  48 ;;;
  49 ;;; This module supports "device mapping", a concept implemented by Linux's
  50 ;;; device-mapper.
  51 ;;;
  52 ;;; Code:
  53
  54 (define-record-type* <mapped-device> mapped-device
  55   make-mapped-device
  56   mapped-device?
  57   (source    mapped-device-source)                ;string
  58   (target    mapped-device-target)                ;string
  59   (type      mapped-device-type))                 ;<mapped-device-kind>
  60
  61 (define-record-type* <mapped-device-type> mapped-device-kind
  62   make-mapped-device-kind
  63   mapped-device-kind?
  64   (open      mapped-device-kind-open)             ;source target -> gexp
  65   (close     mapped-device-kind-close             ;source target -> gexp
  66              (default (const #~(const #f)))))
  67
  68 \f
  69 ;;;
  70 ;;; Device mapping as a Shepherd service.
  71 ;;;
  72
  73 (define device-mapping-service-type
  74   (shepherd-service-type
  75    'device-mapping
  76    (match-lambda
  77      (($ <mapped-device> source target
  78                          ($ <mapped-device-type> open close))
  79       (shepherd-service
  80        (provision (list (symbol-append 'device-mapping- (string->symbol target))))
  81        (requirement '(udev))
  82        (documentation "Map a device node using Linux's device mapper.")
  83        (start #~(lambda () #$(open source target)))
  84        (stop #~(lambda _ (not #$(close source target))))
  85        (respawn? #f))))))
  86
  87 (define (device-mapping-service mapped-device)
  88   "Return a service that sets up @var{mapped-device}."
  89   (service device-mapping-service-type mapped-device))
  90
  91 \f
  92 ;;;
  93 ;;; Common device mappings.
  94 ;;;
  95
  96 (define (open-luks-device source target)
  97   "Return a gexp that maps SOURCE to TARGET as a LUKS device, using
  98 'cryptsetup'."
  99   (with-imported-modules (source-module-closure
 100                           '((gnu build file-systems)))
 101     #~(let ((source #$source))
 102         ;; XXX: 'use-modules' should be at the top level.
 103         (use-modules (rnrs bytevectors)           ;bytevector?
 104                      ((gnu build file-systems)
 105                       #:select (find-partition-by-luks-uuid)))
 106
 107         ;; Use 'cryptsetup-static', not 'cryptsetup', to avoid pulling the
 108         ;; whole world inside the initrd (for when we're in an initrd).
 109         (zero? (system* #$(file-append cryptsetup-static "/sbin/cryptsetup")
 110                         "open" "--type" "luks"
 111
 112                         ;; Note: We cannot use the "UUID=source" syntax here
 113                         ;; because 'cryptsetup' implements it by searching the
 114                         ;; udev-populated /dev/disk/by-id directory but udev may
 115                         ;; be unavailable at the time we run this.
 116                         (if (bytevector? source)
 117                             (or (find-partition-by-luks-uuid source)
 118                                 (error "LUKS partition not found" source))
 119                             source)
 120
 121                         #$target)))))
 122
 123 (define (close-luks-device source target)
 124   "Return a gexp that closes TARGET, a LUKS device."
 125   #~(zero? (system* #$(file-append cryptsetup-static "/sbin/cryptsetup")
 126                     "close" #$target)))
 127
 128 (define luks-device-mapping
 129   ;; The type of LUKS mapped devices.
 130   (mapped-device-kind
 131    (open open-luks-device)
 132    (close close-luks-device)))
 133
 134 (define (open-raid-device sources target)
 135   "Return a gexp that assembles SOURCES (a list of devices) to the RAID device
 136 TARGET (e.g., \"/dev/md0\"), using 'mdadm'."
 137   #~(let ((sources '#$sources)
 138
 139           ;; XXX: We're not at the top level here.  We could use a
 140           ;; non-top-level 'use-modules' form but that doesn't work when the
 141           ;; code is eval'd, like the Shepherd does.
 142           (every   (@ (srfi srfi-1) every))
 143           (format  (@ (ice-9 format) format)))
 144       (let loop ((attempts 0))
 145         (unless (every file-exists? sources)
 146           (when (> attempts 20)
 147             (error "RAID devices did not show up; bailing out"
 148                    sources))
 149
 150           (format #t "waiting for RAID source devices~{ ~a~}...~%"
 151                   sources)
 152           (sleep 1)
 153           (loop (+ 1 attempts))))
 154
 155       ;; Use 'mdadm-static' rather than 'mdadm' to avoid pulling its whole
 156       ;; closure (80 MiB) in the initrd when a RAID device is needed for boot.
 157       (zero? (apply system* #$(file-append mdadm-static "/sbin/mdadm")
 158                     "--assemble" #$target sources))))
 159
 160 (define (close-raid-device sources target)
 161   "Return a gexp that stops the RAID device TARGET."
 162   #~(zero? (system* #$(file-append mdadm-static "/sbin/mdadm")
 163                     "--stop" #$target)))
 164
 165 (define raid-device-mapping
 166   ;; The type of RAID mapped devices.
 167   (mapped-device-kind
 168    (open open-raid-device)
 169    (close close-raid-device)))
 170
 171 ;;; mapped-devices.scm ends here