Subject: [PATCH 0/5] Detect missing modules in the initrd

From: Ludovic Courtès <[email-masked]>
Date: Tue, 27 Feb 2018 15:22:40 +0100

Hello Guix!

This patch series aims to allow ‘guix system init’ & co. to detect
kernel modules that are missing from the initrd, which would typically
render the system unbootable.

To do that it adds code in (gnu build linux-modules) to determine the
modules needed for a particular device:

--8<---------------cut here---------------start------------->8---
$ sudo ./pre-inst-env guile
GNU Guile 2.2.3
Copyright (C) 1995-2017 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> ,use (gnu build linux-modules)
scheme@(guile-user)> ,use (srfi srfi-1)
scheme@(guile-user)> (append-map matching-modules (device-module-aliases "/dev/sda2"))
$1 = ("ahci" "ahci")
--8<---------------cut here---------------end--------------->8---

It then adds an ‘initrd-modules’ field to ‘operating-system’ as a way to
expose the list of modules requested for the initrd.

Finally, it augments ‘guix system’ to perform the necessary checks.

It works, but with a few caveats:

  1. ‘device-module-aliases’ returns the empty list for /dev/dm-0, which
     is a LUKS device on my laptop.  I’m not sure what it would take to
     have it return “dm-crypt”, etc.  Same for RAID devices.

  2. Let’s assume you have: (initrd-modules '("a")).  ‘guix system’
     could report that module “b” is missing, even if “b” is actually a
     dependency of “a” and will therefore be automatically included in
     the initrd.  I think that’s an acceptable limitation (fixing it is
     non-trivial since we’d ideally need to build the target kernel so
     we can inspect its modules and determine their closure.)

You’re welcome to give it a try.  In particular it’d be great if you
could check that ‘device-module-aliases’ returns the right thing on your
machine, as I shown in the example above.

Note that, in addition to that, we could also have a tool to generate a
template ‘operating-system’ declaration.  Let’s say:

  guix system template desktop encrypted-root

would generate a config based on the desktop config but with the right
‘initrd-modules’.

Feedback & suggestions welcome!

Ludo’.

Ludovic Courtès (5):
  Add (guix glob).
  linux-modules: Add 'device-module-aliases' and related procedures.
  linux-initrd: Separate file system module logic.
  system: Add 'initrd-modules' field.
  guix system: Check for the lack of modules in the initrd.

 Makefile.am                   |   4 +-
 doc/guix.texi                 |  42 ++++++++---
 gnu/build/linux-modules.scm   | 161 +++++++++++++++++++++++++++++++++++++++++-
 gnu/system.scm                |   8 +++
 gnu/system/install.scm        |   7 +-
 gnu/system/linux-initrd.scm   |  94 ++++++++++++++----------
 gnu/system/mapped-devices.scm |  53 ++++++++++----
 gnu/tests/install.scm         |  11 ++-
 guix/glob.scm                 |  97 +++++++++++++++++++++++++
 guix/scripts/system.scm       |  67 +++++++++++++++---
 tests/glob.scm                |  58 +++++++++++++++
 11 files changed, 519 insertions(+), 83 deletions(-)
 create mode 100644 guix/glob.scm
 create mode 100644 tests/glob.scm

-- 
2.16.2