guix system: Add 'reconfigure' action.

* guix/scripts/system.scm (%system-profile): New variable.
  (switch-to-system, previous-grub-entries): New procedures.
  (unless-file-not-found): New macro.
  (show-help): Add 'reconfigure'.
  (guix-system): Handle it.
* gnu/system.scm: Export 'operating-system-activation-script'.
* doc/guix.texi (Invoking guix system): Document it.

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 446c688679..76a812f23c 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -3210,6 +3210,18 @@ operating system is instantiate.  Currently the following values are
 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 GNU.}.
+
+This effects all the configuration specified in @var{file}: user
+accounts, system services, global package list, setuid programs, etc.
+
+It also adds a GRUB menu entry for the new OS configuration, and moves
+entries for older configurations to a submenu---unless
+@option{--no-grub} is passed.
+
 @item build
 Build the operating system's derivation, which includes all the
 configuration files and programs needed to boot and run the system.