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-rw-r--r--doc/guix.texi51
-rw-r--r--guix/scripts/system.scm95
2 files changed, 138 insertions, 8 deletions
diff --git a/doc/guix.texi b/doc/guix.texi
index 1075a7e178..b8cb01f48a 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -11155,8 +11155,9 @@ supported:
@table @code
@item reconfigure
Build the operating system described in @var{file}, activate it, and
-switch to it@footnote{This action is usable only on systems already
-running GuixSD.}.
+switch to it@footnote{This action (and the related actions
+@code{switch-generation} and @code{roll-back}) are usable only on
+systems already running GuixSD.}.
This effects all the configuration specified in @var{file}: user
accounts, system services, global package list, setuid programs, etc.
@@ -11178,6 +11179,52 @@ guix pull}). Failing to do that you would see an older version of Guix
once @command{reconfigure} has completed.
@end quotation
+@item switch-generation
+Switch to an existing system generation. This action atomically
+switches the system profile to the specified system generation. It also
+rearranges the system's existing GRUB menu entries. It makes the menu
+entry for the specified system generation the default, and it moves the
+entries for the other generations to a submenu. The next time the
+system boots, it will use the specified system generation.
+
+The target generation can be specified explicitly by its generation
+number. For example, the following invocation would switch to system
+generation 7:
+
+@example
+guix system switch-generation 7
+@end example
+
+The target generation can also be specified relative to the current
+generation with the form @code{+N} or @code{-N}, where @code{+3} means
+``3 generations ahead of the current generation,'' and @code{-1} means
+``1 generation prior to the current generation.'' When specifying a
+negative value such as @code{-1}, you must precede it with @code{--} to
+prevent it from being parsed as an option. For example:
+
+@example
+guix system switch-generation -- -1
+@end example
+
+Currently, the effect of invoking this action is @emph{only} to switch
+the system profile to an existing generation and rearrange the GRUB menu
+entries. To actually start using the target system generation, you must
+reboot after running this action. In the future, it will be updated to
+do the same things as @command{reconfigure}, like activating and
+deactivating services.
+
+This action will fail if the specified generation does not exist.
+
+@item roll-back
+Switch to the preceding system generation. The next time the system
+boots, it will use the preceding system generation. This is the inverse
+of @command{reconfigure}, and it is exactly the same as invoking
+@command{switch-generation} with an argument of @code{-1}.
+
+Currently, as with @command{switch-generation}, you must reboot after
+running this action to actually start using the preceding system
+generation.
+
@item build
Build the derivation of the operating system, which includes all the
configuration files and programs needed to boot and run the system.
diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index 5bc40ed735..df9b37d544 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -407,6 +407,65 @@ NUMBERS, which is a list of generation numbers."
;;;
+;;; Roll-back.
+;;;
+(define (roll-back-system store)
+ "Roll back the system profile to its previous generation. STORE is an open
+connection to the store."
+ (switch-to-system-generation store "-1"))
+
+;;;
+;;; Switch generations.
+;;;
+(define (switch-to-system-generation store spec)
+ "Switch the system profile to the generation specified by SPEC, and
+re-install grub with a grub configuration file that uses the specified system
+generation as its default entry. STORE is an open connection to the store."
+ (let ((number (relative-generation-spec->number %system-profile spec)))
+ (if number
+ (begin
+ (reinstall-grub store number)
+ (switch-to-generation* %system-profile number))
+ (leave (_ "cannot switch to system generation '~a'~%") spec))))
+
+(define (reinstall-grub store number)
+ "Re-install grub for existing system profile generation NUMBER. STORE is an
+open connection to the store."
+ (let* ((generation (generation-file-name %system-profile number))
+ (file (string-append generation "/parameters"))
+ (params (unless-file-not-found
+ (call-with-input-file file read-boot-parameters)))
+ (root-device (boot-parameters-root-device params))
+ ;; We don't currently keep track of past menu entries' details. The
+ ;; default values will allow the system to boot, even if they differ
+ ;; from the actual past values for this generation's entry.
+ (grub-config (grub-configuration (device root-device)))
+ ;; Make the specified system generation the default entry.
+ (entries (profile-grub-entries %system-profile (list number)))
+ (old-generations (delv number (generation-numbers %system-profile)))
+ (old-entries (profile-grub-entries %system-profile old-generations))
+ (grub.cfg (run-with-store store
+ (grub-configuration-file grub-config
+ entries
+ #:old-entries old-entries))))
+ (show-what-to-build store (list grub.cfg))
+ (build-derivations store (list grub.cfg))
+ ;; This is basically the same as install-grub*, but for now we avoid
+ ;; re-installing the GRUB boot loader itself onto a device, mainly because
+ ;; we don't in general have access to the same version of the GRUB package
+ ;; which was used when installing this other system generation.
+ (let* ((grub.cfg-path (derivation->output-path grub.cfg))
+ (gc-root (string-append %gc-roots-directory "/grub.cfg"))
+ (temp-gc-root (string-append gc-root ".new")))
+ (switch-symlinks temp-gc-root grub.cfg-path)
+ (unless (false-if-exception (install-grub-config grub.cfg-path "/"))
+ (delete-file temp-gc-root)
+ (leave (_ "failed to re-install GRUB configuration file: '~a'~%")
+ grub.cfg-path))
+ (rename-file temp-gc-root gc-root))))
+
+
+;;;
;;; Graphs.
;;;
@@ -641,14 +700,19 @@ building anything."
;;;
(define (show-help)
- (display (_ "Usage: guix system [OPTION] ACTION [FILE]
-Build the operating system declared in FILE according to ACTION.\n"))
+ (display (_ "Usage: guix system [OPTION ...] ACTION [ARG ...] [FILE]
+Build the operating system declared in FILE according to ACTION.
+Some ACTIONS support additional ARGS.\n"))
(newline)
(display (_ "The valid values for ACTION are:\n"))
(newline)
(display (_ "\
reconfigure switch to a new operating system configuration\n"))
(display (_ "\
+ roll-back switch to the previous operating system configuration\n"))
+ (display (_ "\
+ switch-generation switch to an existing operating system configuration\n"))
+ (display (_ "\
list-generations list the system generations\n"))
(display (_ "\
build build the operating system without installing anything\n"))
@@ -809,15 +873,33 @@ resulting from command-line parsing."
"Process COMMAND, one of the 'guix system' sub-commands. ARGS is its
argument list and OPTS is the option alist."
(case command
+ ;; The following commands do not need to use the store, and they do not need
+ ;; an operating system configuration file.
((list-generations)
- ;; List generations. No need to connect to the daemon, etc.
(let ((pattern (match args
(() "")
((pattern) pattern)
(x (leave (_ "wrong number of arguments~%"))))))
(list-generations pattern)))
- (else
- (process-action command args opts))))
+ ;; The following commands need to use the store, but they do not need an
+ ;; operating system configuration file.
+ ((switch-generation)
+ (let ((pattern (match args
+ ((pattern) pattern)
+ (x (leave (_ "wrong number of arguments~%"))))))
+ (with-store store
+ (set-build-options-from-command-line store opts)
+ (switch-to-system-generation store pattern))))
+ ((roll-back)
+ (let ((pattern (match args
+ (() "")
+ (x (leave (_ "wrong number of arguments~%"))))))
+ (with-store store
+ (set-build-options-from-command-line store opts)
+ (roll-back-system store))))
+ ;; The following commands need to use the store, and they also
+ ;; need an operating system configuration file.
+ (else (process-action command args opts))))
(define (guix-system . args)
(define (parse-sub-command arg result)
@@ -827,7 +909,8 @@ argument list and OPTS is the option alist."
(let ((action (string->symbol arg)))
(case action
((build container vm vm-image disk-image reconfigure init
- extension-graph shepherd-graph list-generations)
+ extension-graph shepherd-graph list-generations roll-back
+ switch-generation)
(alist-cons 'action action result))
(else (leave (_ "~a: unknown action~%") action))))))