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authorLudovic Courtès <ludo@gnu.org>2018-09-07 09:50:26 +0200
committerLudovic Courtès <ludo@gnu.org>2018-09-07 11:40:05 +0200
commit1540075c790dfaeff52c93392f2fc63b9e23b77e (patch)
treedc9c011af6bd8a6cdde92f84e0eb5ed9da957c6e
parent0012e0dd5642fbbb8ee40a68f65afc184952fc98 (diff)
downloadguix-1540075c790dfaeff52c93392f2fc63b9e23b77e.tar
guix-1540075c790dfaeff52c93392f2fc63b9e23b77e.tar.gz
vm: Make UUID computation really deterministic.
Fixes <https://bugs.gnu.org/32652>. * gnu/system/vm.scm (operating-system-uuid)[service-name, file-system-digest]: New procedures. Map these over services and file systems and hash the result. * tests/guix-system.sh: Add test.
-rw-r--r--gnu/system/vm.scm33
-rw-r--r--tests/guix-system.sh8
2 files changed, 37 insertions, 4 deletions
diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
index 3898872a46..91e117b9f3 100644
--- a/gnu/system/vm.scm
+++ b/gnu/system/vm.scm
@@ -529,17 +529,42 @@ should set REGISTER-CLOSURES? to #f."
(define* (operating-system-uuid os #:optional (type 'dce))
"Compute UUID object with a deterministic \"UUID\" for OS, of the given
TYPE (one of 'iso9660 or 'dce). Return a UUID object."
+ ;; Note: For this to be deterministic, we must not hash things that contains
+ ;; (directly or indirectly) procedures, for example. That rules out
+ ;; anything that contains gexps, thunk or delayed record fields, etc.
+
+ (define service-name
+ (compose service-type-name service-kind))
+
+ (define (file-system-digest fs)
+ ;; Return a hashable digest that does not contain 'dependencies' since
+ ;; this field can contain procedures.
+ (let ((device (file-system-device fs)))
+ (list (file-system-mount-point fs)
+ (file-system-type fs)
+ (cond ((file-system-label? device)
+ (file-system-label->string device))
+ ((uuid? device)
+ (uuid->string device))
+ ((string? device)
+ device)
+ (else #f))
+ (file-system-options fs))))
+
(if (eq? type 'iso9660)
(let ((pad (compose (cut string-pad <> 2 #\0)
number->string))
- (h (hash (operating-system-services os) 3600)))
+ (h (hash (map service-name (operating-system-services os))
+ 3600)))
(bytevector->uuid
(string->iso9660-uuid
(string-append "1970-01-01-"
(pad (hash (operating-system-host-name os) 24)) "-"
(pad (quotient h 60)) "-"
(pad (modulo h 60)) "-"
- (pad (hash (operating-system-file-systems os) 100))))
+ (pad (hash (map file-system-digest
+ (operating-system-file-systems os))
+ 100))))
'iso9660))
(bytevector->uuid
(uint-list->bytevector
@@ -547,9 +572,9 @@ TYPE (one of 'iso9660 or 'dce). Return a UUID object."
(- (expt 2 32) 1))
(hash (operating-system-host-name os)
(- (expt 2 32) 1))
- (hash (operating-system-services os)
+ (hash (map service-name (operating-system-services os))
(- (expt 2 32) 1))
- (hash (operating-system-file-systems os)
+ (hash (map file-system-digest (operating-system-file-systems os))
(- (expt 2 32) 1)))
(endianness little)
4)
diff --git a/tests/guix-system.sh b/tests/guix-system.sh
index 36ba5fbd5f..a129efdfcb 100644
--- a/tests/guix-system.sh
+++ b/tests/guix-system.sh
@@ -232,6 +232,14 @@ guix system build "$tmpfile" -d | grep '\.drv$'
guix system vm "$tmpfile" -d # succeeds
guix system vm "$tmpfile" -d | grep '\.drv$'
+# Make sure the behavior is deterministic (<https://bugs.gnu.org/32652>).
+drv1="`guix system vm "$tmpfile" -d`"
+drv2="`guix system vm "$tmpfile" -d`"
+test "$drv1" = "$drv2"
+drv1="`guix system disk-image --file-system-type=iso9660 "$tmpfile" -d`"
+drv2="`guix system disk-image --file-system-type=iso9660 "$tmpfile" -d`"
+test "$drv1" = "$drv2"
+
make_user_config "group-that-does-not-exist" "users"
if guix system build "$tmpfile" -n 2> "$errorfile"
then false