linux-initrd: Add a raw-initrd and use it to define base-initrd.

* gnu/system/linux-initrd.scm (raw-initrd): New exported variable.
(base-initrd): Use raw-initrd to build the initrd.
* doc/guix.texi (Initial RAM Disk): Document it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

2 files changed, 114 insertions, 62 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index b6c89bc9b6..a602c701cb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -13887,9 +13887,9 @@ kernel modules that may be needed to achieve that.
 
 The @code{initrd} field of an @code{operating-system} declaration allows
 you to specify which initrd you would like to use.  The @code{(gnu
-system linux-initrd)} module provides two ways to build an initrd: the
-high-level @code{base-initrd} procedure, and the low-level
-@code{expression->initrd} procedure.
+system linux-initrd)} module provides three ways to build an initrd: the
+high-level @code{base-initrd} procedure and the low-level
+@code{raw-initrd} and @code{expression->initrd} procedures.
 
 The @code{base-initrd} procedure is intended to cover most common uses.
 For example, if you want to add a bunch of kernel modules to be loaded
@@ -13910,9 +13910,16 @@ The @code{base-initrd} procedure also handles common use cases that
 involves using the system as a QEMU guest, or as a ``live'' system with
 volatile root file system.
 
-The initial RAM disk produced by @code{base-initrd} honors several
-options passed on the Linux kernel command line (that is, arguments
-passed @i{via} the @code{linux} command of GRUB, or the
+The @code{base-initrd} procedure is built from @code{raw-initrd} procedure.
+Unlike @code{base-initrd}, @code{raw-initrd} doesn't do anything high-level,
+such as trying to guess which kernel modules and packages should be included
+to the initrd. An example use of @code{raw-initrd} is when a user has
+a custom Linux kernel configuration and default kernel modules included by
+@code{base-initrd} are not available.
+
+The initial RAM disk produced by @code{base-initrd} or @code{raw-initrd}
+honors several options passed on the Linux kernel command line
+(that is, arguments passed @i{via} the @code{linux} command of GRUB, or the
 @code{-append} option of QEMU), notably:
 
 @table @code
@@ -13951,19 +13958,23 @@ Manual}, for more information on Guile's REPL.
 @end table
 
 Now that you know all the features that initial RAM disks produced by
-@code{base-initrd} provide, here is how to use it and customize it
-further.
+@code{base-initrd} and @code{raw-initrd} provide,
+here is how to use it and customize it further.
 
 @cindex initrd
 @cindex initial RAM disk
-@deffn {Monadic Procedure} base-initrd @var{file-systems} @
-       [#:qemu-networking? #f] [#:virtio? #t] [#:volatile-root? #f] @
-       [#:extra-modules '()] [#:mapped-devices '()]
-Return a monadic derivation that builds a generic initrd.  @var{file-systems} is
+@deffn {Monadic Procedure} raw-initrd @var{file-systems} @
+       [#:linux-modules '()] [#:mapped-devices '()] @
+       [#:helper-packages '()] [#:qemu-networking? #f] [#:volatile-root? #f]
+Return a monadic derivation that builds a raw initrd.  @var{file-systems} is
 a list of file systems to be mounted by the initrd, possibly in addition to
 the root file system specified on the kernel command line via @code{--root}.
+@var{linux-modules} is a list of kernel modules to be loaded at boot time.
 @var{mapped-devices} is a list of device mappings to realize before
 @var{file-systems} are mounted (@pxref{Mapped Devices}).
+@var{helper-packages} is a list of packages to be copied in the initrd. It may
+include @code{e2fsck/static} or other packages needed by the initrd to check
+root partition.
 
 When @var{qemu-networking?} is true, set up networking with the standard QEMU
 parameters.  When @var{virtio?} is true, load additional modules so that the
@@ -13971,6 +13982,18 @@ initrd can be used as a QEMU guest with para-virtualized I/O drivers.
 
 When @var{volatile-root?} is true, the root file system is writable but any changes
 to it are lost.
+@end deffn
+
+@deffn {Monadic Procedure} base-initrd @var{file-systems} @
+       [#:mapped-devices '()] [#:qemu-networking? #f] [#:volatile-root? #f]@
+       [#:virtio? #t] [#:extra-modules '()]
+Return a monadic derivation that builds a generic initrd.  @var{file-systems} is
+a list of file systems to be mounted by the initrd like for @code{raw-initrd}.
+@var{mapped-devices}, @var{qemu-networking?} and @var{volatile-root?}
+also behaves as in @code{raw-initrd}.
+
+When @var{virtio?} is true, load additional modules so that the
+initrd can be used as a QEMU guest with para-virtualized I/O drivers.
 
 The initrd is automatically populated with all the kernel modules necessary
 for @var{file-systems} and for the given options.  However, additional kernel
diff --git a/gnu/system/linux-initrd.scm b/gnu/system/linux-initrd.scm
index 4a753cdadb..81c1278c0c 100644
--- a/gnu/system/linux-initrd.scm
+++ b/gnu/system/linux-initrd.scm
@@ -2,6 +2,7 @@
 ;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
+;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -41,6 +42,7 @@
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:export (expression->initrd
+            raw-initrd
             base-initrd))
 
 
@@ -131,13 +133,79 @@ MODULES and taken from LINUX."
 
   (gexp->derivation "linux-modules" build-exp))
 
+(define* (raw-initrd file-systems
+                      #:key
+                      (linux linux-libre)
+                      (linux-modules '())
+                      (mapped-devices '())
+                      (helper-packages '())
+                      qemu-networking?
+                      volatile-root?)
+  "Return a monadic derivation that builds a raw initrd, with kernel
+modules taken from LINUX.  FILE-SYSTEMS is a list of file-systems to be
+mounted by the initrd, possibly in addition to the root file system specified
+on the kernel command line via '--root'. LINUX-MODULES is a list of kernel
+modules to be loaded at boot time. MAPPED-DEVICES is a list of device
+mappings to realize before FILE-SYSTEMS are mounted.
+HELPER-PACKAGES is a list of packages to be copied in the initrd. It may include
+e2fsck/static or other packages needed by the initrd to check root partition.
+
+When QEMU-NETWORKING? is true, set up networking with the standard QEMU
+parameters.
+When VOLATILE-ROOT? is true, the root file system is writable but any changes
+to it are lost."
+  (define device-mapping-commands
+    ;; List of gexps to open the mapped devices.
+    (map (lambda (md)
+           (let* ((source (mapped-device-source md))
+                  (target (mapped-device-target md))
+                  (type   (mapped-device-type md))
+                  (open   (mapped-device-kind-open type)))
+             (open source target)))
+         mapped-devices))
+
+  (mlet %store-monad ((kodir (flat-linux-module-directory linux
+                                                          linux-modules)))
+    (expression->initrd
+     (with-imported-modules (source-module-closure
+                             '((gnu build linux-boot)
+                               (guix build utils)
+                               (guix build bournish)
+                               (gnu build file-systems)))
+       #~(begin
+           (use-modules (gnu build linux-boot)
+                        (guix build utils)
+                        (guix build bournish) ;add the 'bournish' meta-command
+                        (srfi srfi-26)
+
+                        ;; FIXME: The following modules are for
+                        ;; LUKS-DEVICE-MAPPING.  We should instead propagate
+                        ;; this info via gexps.
+                        ((gnu build file-systems)
+                         #:select (find-partition-by-luks-uuid))
+                        (rnrs bytevectors))
+
+           (with-output-to-port (%make-void-port "w")
+             (lambda ()
+               (set-path-environment-variable "PATH" '("bin" "sbin")
+                                              '#$helper-packages)))
+
+           (boot-system #:mounts '#$(map file-system->spec file-systems)
+                        #:pre-mount (lambda ()
+                                      (and #$@device-mapping-commands))
+                        #:linux-modules '#$linux-modules
+                        #:linux-module-directory '#$kodir
+                        #:qemu-guest-networking? #$qemu-networking?
+                        #:volatile-root? '#$volatile-root?)))
+     #:name "raw-initrd")))
+
 (define* (base-initrd file-systems
                       #:key
                       (linux linux-libre)
                       (mapped-devices '())
                       qemu-networking?
-                      (virtio? #t)
                       volatile-root?
+                      (virtio? #t)
                       (extra-modules '()))
   "Return a monadic derivation that builds a generic initrd, with kernel
 modules taken from LINUX.  FILE-SYSTEMS is a list of file-systems to be
@@ -145,14 +213,12 @@ mounted by the initrd, possibly in addition to the root file system specified
 on the kernel command line via '--root'.  MAPPED-DEVICES is a list of device
 mappings to realize before FILE-SYSTEMS are mounted.
 
-When QEMU-NETWORKING? is true, set up networking with the standard QEMU
-parameters.  When VIRTIO? is true, load additional modules so the initrd can
+QEMU-NETWORKING? and VOLATILE-ROOT? behaves as in raw-initrd.
+
+When VIRTIO? is true, load additional modules so the initrd can
 be used as a QEMU guest with the root file system on a para-virtualized block
 device.
 
-When VOLATILE-ROOT? is true, the root file system is writable but any changes
-to it are lost.
-
 The initrd is automatically populated with all the kernel modules necessary
 for FILE-SYSTEMS and for the given options.  However, additional kernel
 modules can be listed in EXTRA-MODULES.  They will be added to the initrd, and
@@ -224,49 +290,12 @@ loaded at boot time in the order in which they appear."
             (list unionfs-fuse/static)
             '())))
 
-  (define device-mapping-commands
-    ;; List of gexps to open the mapped devices.
-    (map (lambda (md)
-           (let* ((source (mapped-device-source md))
-                  (target (mapped-device-target md))
-                  (type   (mapped-device-type md))
-                  (open   (mapped-device-kind-open type)))
-             (open source target)))
-         mapped-devices))
-
-  (mlet %store-monad ((kodir (flat-linux-module-directory linux
-                                                          linux-modules)))
-    (expression->initrd
-     (with-imported-modules (source-module-closure
-                             '((gnu build linux-boot)
-                               (guix build utils)
-                               (guix build bournish)
-                               (gnu build file-systems)))
-       #~(begin
-           (use-modules (gnu build linux-boot)
-                        (guix build utils)
-                        (guix build bournish) ;add the 'bournish' meta-command
-                        (srfi srfi-26)
-
-                        ;; FIXME: The following modules are for
-                        ;; LUKS-DEVICE-MAPPING.  We should instead propagate
-                        ;; this info via gexps.
-                        ((gnu build file-systems)
-                         #:select (find-partition-by-luks-uuid))
-                        (rnrs bytevectors))
-
-           (with-output-to-port (%make-void-port "w")
-             (lambda ()
-               (set-path-environment-variable "PATH" '("bin" "sbin")
-                                              '#$helper-packages)))
-
-           (boot-system #:mounts '#$(map file-system->spec file-systems)
-                        #:pre-mount (lambda ()
-                                      (and #$@device-mapping-commands))
-                        #:linux-modules '#$linux-modules
-                        #:linux-module-directory '#$kodir
-                        #:qemu-guest-networking? #$qemu-networking?
-                        #:volatile-root? '#$volatile-root?)))
-     #:name "base-initrd")))
+  (raw-initrd file-systems
+              #:linux linux
+              #:linux-modules linux-modules
+              #:mapped-devices mapped-devices
+              #:helper-packages helper-packages
+              #:qemu-networking? qemu-networking?
+              #:volatile-root? volatile-root?))
 
 ;;; linux-initrd.scm ends here