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install: Use overlayfs instead of unionfs.

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I dediced to keep adding /tmp as tmpfs since I was not able to trigger bug
while still using unionfs, so I could not verify whether this mount is still
needed with overlayfs.  Mapping /tmp to tmpfs does not harm, so we are on the
save side.

* gnu/system/install.scm (make-cow-store): Mount /gnu/store without additional
  read-only bind-mount, since in overlayfs the "lower" level is always
  read-only. Add work-dir required by overlayfs. No need to sleep anymore
  since now using the mount syscall. [unionfs]: Remove now unused function.
  (%installation-services): Update comment.
  (installation-os)[file-systems]: Update comment.
This commit is contained in:
Hartmut Goebel 2017-10-27 15:33:38 +02:00
parent c828969036
commit d9565f7d87
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1 changed files with 17 additions and 30 deletions
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47
gnu/system/install.scm
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@ -71,19 +71,6 @@ (define (make-cow-store target)
"Return a gexp that makes 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 (unionfs read-only read-write mount-point)
;; Make MOUNT-POINT the union of READ-ONLY and READ-WRITE.
;; Note: in the command below, READ-WRITE appears before READ-ONLY so that
;; it is considered a "higher-level branch", as per unionfs-fuse(8),
;; thereby allowing files existing on READ-ONLY to be copied over to
;; READ-WRITE.
#~(fork+exec-command
(list (string-append #$unionfs-fuse "/bin/unionfs")
"-o"
"cow,allow_other,use_ino,max_files=65536,nonempty"
(string-append #$read-write "=RW:" #$read-only "=RO")
#$mount-point)))
(define (set-store-permissions directory)
;; Set the right perms on DIRECTORY to use it as the store.
@ -97,23 +84,21 @@ (define (set-store-permissions directory)
(mkdir-p tmpdir)
(mount tmpdir "/tmp" "none" MS_BIND))
(unless (file-exists? "/.ro-store")
(mkdir "/.ro-store")
(mount #$(%store-prefix) "/.ro-store" "none"
(logior MS_BIND MS_RDONLY)))
(let ((rw-dir (string-append target #$%backing-directory)))
(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)
#$(set-store-permissions "/.rw-store")
;; Mount the union, then atomically make it the store.
(and #$(unionfs "/.ro-store" #~rw-dir "/.rw-store")
(begin
(sleep 1) ;XXX: wait for unionfs to be ready
(mount "/.rw-store" #$(%store-prefix) "" MS_MOVE)
(rmdir "/.rw-store"))))))
;; Mount the overlay, then atomically make it the store.
(mount "none" "/.rw-store" "overlay" 0
(string-append "lowerdir=" #$(%store-prefix) ","
"upperdir=" rw-dir ","
"workdir=" work-dir))
(mount "/.rw-store" #$(%store-prefix) "" MS_MOVE)
(rmdir "/.rw-store"))))
(define cow-store-service-type
(shepherd-service-type
@ -278,7 +263,7 @@ (define bare-bones-os
(allow-empty-passwords? #f)
(password-authentication? #t)))
;; Since this is running on a USB stick with a unionfs as the root
;; Since this is running on a USB stick with a overlayfs as the root
;; file system, use an appropriate cache configuration.
(nscd-service (nscd-configuration
(caches %nscd-minimal-caches)))
@ -317,10 +302,12 @@ (define installation-os
(title 'label)
(type "ext4"))
;; Make /tmp a tmpfs instead of keeping the unionfs. This is
;; because FUSE creates '.fuse_hiddenXYZ' files for each open file,
;; and this confuses Guix's test suite, for instance. See
;; <http://bugs.gnu.org/23056>.
;; Make /tmp a tmpfs instead of keeping the overlayfs. This
;; originally was used for unionfs because FUSE creates
;; '.fuse_hiddenXYZ' files for each open file, and this confuses
;; Guix's test suite, for instance (see
;; <http://bugs.gnu.org/23056>). We keep this for overlayfs to be
;; on the save side.
(file-system
(mount-point "/tmp")
(device "none")