[bug#29932] [PATCH 0/2] Clean up operating-system-kernel-arguments.

[Danny Milosavljevic]

Hi Ludo,

>   #~(string-append "--system=" #$os)
> 
> where ‘os’ is an <operating-system>.  It automatically computes its
> derivation.  Thus, no need to explicitly call
> ‘operating-system-derivation’ and pass “system.drv” arguments around.

Ah!  Good to know.

> So we’d just need a slight adjustment to ‘bootable-kernel-arguments’ (so
> that it takes the root device from the given OS object) and then rename
> it to ‘operating-system-kernel-arguments’.

bootable-kernel-arguments is also used by the "parameters" file serializer.

Also, the user that is modifying a <operating-system> instance (for example 
marionette-operating-system adding "panic=1") would erronously use 
operating-system-kernel-arguments in order to get the previous instance's 
arguments, resulting in the "--root", "--load" etc being prepended twice, no?

The user might want to pass some kernel arguments which have nothing to do with 
Guix (which <operating-system>'s "kernel-arguments" is for) and then GuixSD 
needs some extra arguments to be able to boot the actual system (which can be 
found entirely automatically - nice!).

Example:

diff --git a/gnu/tests.scm b/gnu/tests.scm
index 0caa922fd..3e4c3d4e3 100644
--- a/gnu/tests.scm
+++ b/gnu/tests.scm
@@ -172,6 +172,14 @@ marionette service in the guest is started after the 
Shepherd services listed
 in REQUIREMENTS."
   (operating-system
     (inherit os)
+    ;; Make sure the guest dies on error.
+    (kernel-arguments (cons "panic=1"
+                            (operating-system-user-kernel-arguments os)))
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    ;; Make sure the guest doesn't hang in the REPL on error.
+    (initrd (lambda (fs . rest)
+              (apply (operating-system-initrd os) fs
+                     #:on-error 'backtrace
+                     rest)))
     (services (cons (service marionette-service-type
                              (marionette-configuration
                               (requirements requirements)

I'd suggest this:

diff --git a/gnu/system.scm b/gnu/system.scm
index df89ca06d..6466c7c48 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -73,7 +73,8 @@
             operating-system-hosts-file
             operating-system-kernel
             operating-system-kernel-file
-            operating-system-kernel-arguments
+            operating-system-bootable-kernel-arguments
+            operating-system-user-kernel-arguments
             operating-system-initrd
             operating-system-users
             operating-system-groups
@@ -200,12 +201,13 @@ booted from ROOT-DEVICE"
   (sudoers-file operating-system-sudoers-file     ; file-like
                 (default %sudoers-specification)))
 
-(define (operating-system-kernel-arguments os system.drv root-device)
-  "Return all the kernel arguments, including the ones not specified
-directly by the user."
-  (bootable-kernel-arguments (operating-system-user-kernel-arguments os)
-                             system.drv
-                             root-device))
+(define* (operating-system-bootable-kernel-arguments os)
+  "Prepend extra arguments to OS's kernel-arguments that allow OS to be 
booted."
+  (let* ((root-file-system (operating-system-root-file-system os))
+         (root-device (file-system-device root-file-system)))
+    #~(bootable-kernel-arguments (operating-system-user-kernel-arguments os)
+                                 #$os
+                                 root-device)))
 
 ^L
 ;;;
@@ -940,7 +942,7 @@ kernel arguments for that derivation to <boot-parameters>."
              (kernel (operating-system-kernel-file os))
              (kernel-arguments
               (if system.drv
-                (operating-system-kernel-arguments os system.drv root-device)
+                (operating-system-bootable-kernel-arguments os)
                 (operating-system-user-kernel-arguments os)))
              (initrd initrd)
              (bootloader-name bootloader-name)
diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
index 496f2ac4e..117e333a7 100644
--- a/gnu/system/vm.scm
+++ b/gnu/system/vm.scm
@@ -716,7 +716,7 @@ it is mostly useful when FULL-BOOT?  is true."
                                 #:disk-image-size disk-image-size)))
     (define kernel-arguments
       #~(list #$@(if graphic? #~() #~("console=ttyS0"))
-              #+@(operating-system-kernel-arguments os os-drv "/dev/vda1")))
+              #+@(operating-system-bootable-kernel-arguments os)))
 
     (define qemu-exec
       #~(list (string-append #$qemu "/bin/" #$(qemu-command (%current-system)))