vm: Estimate the disk size by default.

* gnu/build/vm.scm (estimated-partition-size): New procedure.
* gnu/system/vm.scm (expression->derivation-in-linux-vm):
Change #:disk-image-size default to 'guess.
[builder]: When DISK-IMAGE-SIZE is 'guess, use
'estimated-partition-size' and compute and estimate of the image size.
(qemu-image): Likewise.
* guix/build/store-copy.scm (file-size, closure-size): New procedures.
* guix/scripts/system.scm (%default-options): Change 'image-size' to
'guess.
* doc/guix.texi (Building the Installation Image): Remove '--image-size'
flag from example.
(Invoking guix system): Document the image size estimate.

1 files changed, 34 insertions, 1 deletions

diff --git a/guix/build/store-copy.scm b/guix/build/store-copy.scm
index a296bdf78f..fe2eb6f69a 100644
--- a/guix/build/store-copy.scm
+++ b/guix/build/store-copy.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -20,7 +20,9 @@
   #:use-module (guix build utils)
   #:use-module (srfi srfi-1)
   #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 ftw)
   #:export (read-reference-graph
+            closure-size
             populate-store))
 
 ;;; Commentary:
@@ -46,6 +48,37 @@ The data at PORT is the format produced by #:references-graphs."
            (loop (read-line port)
                  result)))))
 
+(define (file-size file)
+  "Return the size of bytes of FILE, entering it if FILE is a directory."
+  (file-system-fold (const #t)
+                    (lambda (file stat result)    ;leaf
+                      (+ (stat:size stat) result))
+                    (lambda (directory stat result) ;down
+                      (+ (stat:size stat) result))
+                    (lambda (directory stat result) ;up
+                      result)
+                    (lambda (file stat result)    ;skip
+                      result)
+                    (lambda (file stat errno result)
+                      (format (current-error-port)
+                              "file-size: ~a: ~a~%" file
+                              (strerror errno))
+                      result)
+                    0
+                    file
+                    lstat))
+
+(define (closure-size reference-graphs)
+  "Return an estimate of the size of the closure described by
+REFERENCE-GRAPHS, a list of reference-graph files."
+  (define (graph-from-file file)
+    (call-with-input-file file read-reference-graph))
+
+  (define items
+    (delete-duplicates (append-map graph-from-file reference-graphs)))
+
+  (reduce + 0 (map file-size items)))
+
 (define* (populate-store reference-graphs target)
   "Populate the store under directory TARGET with the items specified in
 REFERENCE-GRAPHS, a list of reference-graph files."