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-rw-r--r--gnu/build/install.scm44
1 files changed, 43 insertions, 1 deletions
diff --git a/gnu/build/install.scm b/gnu/build/install.scm
index 87aa5d68da..63995e1d09 100644
--- a/gnu/build/install.scm
+++ b/gnu/build/install.scm
@@ -18,6 +18,7 @@
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu build install)
+ #:use-module (guix build syscalls)
#:use-module (guix build utils)
#:use-module (guix build store-copy)
#:use-module (srfi srfi-26)
@@ -26,7 +27,9 @@
evaluate-populate-directive
populate-root-file-system
install-database-and-gc-roots
- populate-single-profile-directory))
+ populate-single-profile-directory
+ mount-cow-store
+ unmount-cow-store))
;;; Commentary:
;;;
@@ -229,4 +232,43 @@ This is used to create the self-contained tarballs with 'guix pack'."
(_
#t)))
+(define (mount-cow-store target backing-directory)
+ "Make the store copy-on-write, using TARGET as the backing store. This is
+useful when TARGET is on a hard disk, whereas the current store is on a RAM
+disk."
+ (define (set-store-permissions directory)
+ "Set the right perms on DIRECTORY to use it as the store."
+ (chown directory 0 30000) ;use the fixed 'guixbuild' GID
+ (chmod directory #o1775))
+
+ (let ((tmpdir (string-append target "/tmp")))
+ (mkdir-p tmpdir)
+ (mount tmpdir "/tmp" "none" MS_BIND))
+
+ (let* ((rw-dir (string-append target backing-directory))
+ (work-dir (string-append rw-dir "/../.overlayfs-workdir")))
+ (mkdir-p rw-dir)
+ (mkdir-p work-dir)
+ (mkdir-p "/.rw-store")
+ (set-store-permissions rw-dir)
+ (set-store-permissions "/.rw-store")
+
+ ;; Mount the overlay, then atomically make it the store.
+ (mount "none" "/.rw-store" "overlay" 0
+ (string-append "lowerdir=" (%store-directory) ","
+ "upperdir=" rw-dir ","
+ "workdir=" work-dir))
+ (mount "/.rw-store" (%store-directory) "" MS_MOVE)
+ (rmdir "/.rw-store")))
+
+(define (unmount-cow-store target backing-directory)
+ "Unmount copy-on-write store."
+ (let ((tmp-dir "/remove"))
+ (mkdir-p tmp-dir)
+ (mount (%store-directory) tmp-dir "" MS_MOVE)
+ (umount tmp-dir)
+ (rmdir tmp-dir)
+ (delete-file-recursively
+ (string-append target backing-directory))))
+
;;; install.scm ends here