aboutsummaryrefslogtreecommitdiff
path: root/guix/docker.scm
blob: 060232148ef841fa64057ec25a460ec0ff395bc2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
;;; Copyright © 2017 Ludovic Courtès <ludo@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 the GNU General Public License
;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.

(define-module (guix docker)
  #:use-module (guix hash)
  #:use-module (guix base16)
  #:use-module ((guix build utils)
                #:select (mkdir-p
                          delete-file-recursively
                          with-directory-excursion))
  #:use-module (guix build store-copy)
  #:use-module (srfi srfi-19)
  #:use-module (rnrs bytevectors)
  #:use-module (ice-9 match)
  #:export (build-docker-image))

;; Load Guile-JSON at run time to simplify the job of 'imported-modules' & co.
(module-use! (current-module) (resolve-interface '(json)))

;; Generate a 256-bit identifier in hexadecimal encoding for the Docker image
;; containing the closure at PATH.
(define docker-id
  (compose bytevector->base16-string sha256 string->utf8))

(define (layer-diff-id layer)
  "Generate a layer DiffID for the given LAYER archive."
  (string-append "sha256:" (bytevector->base16-string (file-sha256 layer))))

;; This is the semantic version of the JSON metadata schema according to
;; https://github.com/docker/docker/blob/master/image/spec/v1.2.md
;; It is NOT the version of the image specification.
(define schema-version "1.0")

(define (image-description id time)
  "Generate a simple image description."
  `((id . ,id)
    (created . ,time)
    (container_config . #nil)))

(define (generate-tag path)
  "Generate an image tag for the given PATH."
  (match (string-split (basename path) #\-)
    ((hash name . rest) (string-append name ":" hash))))

(define (manifest path id)
  "Generate a simple image manifest."
  `(((Config . "config.json")
     (RepoTags . (,(generate-tag path)))
     (Layers . (,(string-append id "/layer.tar"))))))

;; According to the specifications this is required for backwards
;; compatibility.  It duplicates information provided by the manifest.
(define (repositories path id)
  "Generate a repositories file referencing PATH and the image ID."
  `((,(generate-tag path) . ((latest . ,id)))))

;; See https://github.com/opencontainers/image-spec/blob/master/config.md
(define (config layer time arch)
  "Generate a minimal image configuration for the given LAYER file."
  ;; "architecture" must be values matching "platform.arch" in the
  ;; runtime-spec at
  ;; https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc2/config.md#platform
  `((architecture . ,arch)
    (comment . "Generated by GNU Guix")
    (created . ,time)
    (config . #nil)
    (container_config . #nil)
    (os . "linux")
    (rootfs . ((type . "layers")
               (diff_ids . (,(layer-diff-id layer)))))))

(define %tar-determinism-options
  ;; GNU tar options to produce archives deterministically.
  '("--sort=name" "--mtime=@1"
    "--owner=root:0" "--group=root:0"))

(define symlink-source
  (match-lambda
    ((source '-> target)
     (string-trim source #\/))))

(define (topmost-component file)
  "Return the topmost component of FILE.  For instance, if FILE is \"/a/b/c\",
return \"a\"."
  (match (string-tokenize file (char-set-complement (char-set #\/)))
    ((first rest ...)
     first)))

(define* (build-docker-image image path
                             #:key closure compressor
                             (symlinks '())
                             (system (utsname:machine (uname)))
                             (creation-time (current-time time-utc)))
  "Write to IMAGE a Docker image archive from the given store PATH.  The image
contains the closure of PATH, as specified in CLOSURE (a file produced by
#:references-graphs).  SYMLINKS must be a list of (SOURCE -> TARGET) tuples
describing symlinks to be created in the image, where each TARGET is relative
to PATH.  SYSTEM is a GNU triplet (or prefix thereof) of the system the
binaries at PATH are for; it is used to produce metadata in the image.

Use COMPRESSOR, a command such as '(\"gzip\" \"-9n\"), to compress IMAGE.  Use
CREATION-TIME, a SRFI-19 time-utc object, as the creation time in metadata."
  (let ((directory "/tmp/docker-image")           ;temporary working directory
        (closure (canonicalize-path closure))
        (id (docker-id path))
        (time (date->string (time-utc->date creation-time) "~4"))
        (arch (let-syntax ((cond* (syntax-rules ()
                                    ((_ (pattern clause) ...)
                                     (cond ((string-prefix? pattern system)
                                            clause)
                                           ...
                                           (else
                                            (error "unsupported system"
                                                   system)))))))
                (cond* ("x86_64" "amd64")
                       ("i686"   "386")
                       ("arm"    "arm")
                       ("mips64" "mips64le")))))
    ;; Make sure we start with a fresh, empty working directory.
    (mkdir directory)

    (and (with-directory-excursion directory
           (mkdir id)
           (with-directory-excursion id
             (with-output-to-file "VERSION"
               (lambda () (display schema-version)))
             (with-output-to-file "json"
               (lambda () (scm->json (image-description id time))))

             ;; Wrap it up.
             (let ((items (call-with-input-file closure
                            read-reference-graph)))
               ;; Create SYMLINKS.
               (for-each (match-lambda
                           ((source '-> target)
                            (let ((source (string-trim source #\/)))
                              (mkdir-p (dirname source))
                              (symlink (string-append path "/" target)
                                       source))))
                         symlinks)

               (and (zero? (apply system* "tar" "-cf" "layer.tar"
                                  (append %tar-determinism-options
                                          items
                                          (map symlink-source symlinks))))
                    (for-each delete-file-recursively
                              (map (compose topmost-component symlink-source)
                                   symlinks)))))

           (with-output-to-file "config.json"
             (lambda ()
               (scm->json (config (string-append id "/layer.tar")
                                  time arch))))
           (with-output-to-file "manifest.json"
             (lambda ()
               (scm->json (manifest path id))))
           (with-output-to-file "repositories"
             (lambda ()
               (scm->json (repositories path id)))))

         (and (zero? (apply system* "tar" "-C" directory "-cf" image
                            `(,@%tar-determinism-options
                              ,@(if compressor
                                    (list "-I" (string-join compressor))
                                    '())
                              ".")))
              (begin (delete-file-recursively directory) #t)))))