system: Record store file system info in each generation.

* gnu/system.scm (<boot-parameters>)[store-device, store-mount-point]:
New fields.
(read-boot-parameters): Initialize them.
(operating-system-grub.cfg): Likewise.  Remove STORE-FS argument from
call to 'grub-configuration-file'.
(operating-system-parameters-file): Add 'store' element in
'boot-parameters'.
* gnu/system/grub.scm (strip-mount-point): Replace 'store-fs' parameter
by 'mount-point'; adjust accordingly.  Adjust callers.
(<menu-entry>)[device, device-mount-point]: New fields.
(eye-candy): Replace 'root-fs' parameter by 'store-device'; add
'store-mount-point'.  Use keyword arguments for 'system' and 'port'.
(grub-root-search): Remove 'root-fs' by 'device' and adjust
accordingly.
(grub-configuration-file): Remove 'store-fs' parameter.  Adjust
accordingly.
* guix/scripts/system.scm (previous-grub-entries): Initialize 'device'
and 'device-mount-point' fields from PARAMS.
* doc/guix.texi (GRUB Configuration): Document 'device' and
'device-mount-point'.  Explain that 'linux' can be prefixed by a GRUB
device name.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 09d206b462..e9ff605711 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -11088,6 +11088,17 @@ The Linux kernel image to boot, for example:
 (file-append linux-libre "/bzImage")
 @end example
 
+It is also possible to specify a device explicitly in the file path
+using GRUB's device naming convention (@pxref{Naming convention,,, grub,
+GNU GRUB manual}), for example:
+
+@example
+"(hd0,msdos1)/boot/vmlinuz"
+@end example
+
+If the device is specified explicitly as above, then the @code{device}
+field is ignored entirely.
+
 @item @code{linux-arguments} (default: @code{()})
 The list of extra Linux kernel command-line arguments---e.g.,
 @code{("console=ttyS0")}.
@@ -11096,6 +11107,22 @@ The list of extra Linux kernel command-line arguments---e.g.,
 A G-Expression or string denoting the file name of the initial RAM disk
 to use (@pxref{G-Expressions}).
 
+@item @code{device} (default: @code{#f})
+The device where the kernel and initrd are to be found---i.e., the GRUB
+@dfn{root} for this menu entry (@pxref{root,,, grub, GNU GRUB manual}).
+
+This may be a file system label (a string), a file system UUID (a
+bytevector, @pxref{File Systems}), or @code{#f}, in which case GRUB will
+search the device containing the file specified by the @code{linux}
+field (@pxref{search,,, grub, GNU GRUB manual}).  It must @emph{not} be
+an OS device name such as @file{/dev/sda1}.
+
+@item @code{device-mount-point} (default: @code{"/"})
+The mount point of the above device on the system.  You probably do not
+need to change the default value.  GuixSD uses it to strip the prefix of
+store file names for systems where @file{/gnu} or @file{/gnu/store} is
+on a separate partition.
+
 @end table
 @end deftp