From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: [PATCH] DISCUSSION: Jookia's Libreboot+LUKS+LVM FDE patch.
Date: Fri, 11 Mar 2016 15:30:10 +0100
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To: Jookia <166291@gmail.com>
Cc: guix-devel@gnu.org

Jookia <166291@gmail.com> skribis:

> I'd really like to discuss how much I needed to break to get the mapped-d=
evices,
> file-systems and swap-devices to just 'work'. I even had to make a functi=
on to
> return a mapped-device type, and have swap-devices not do dependency test=
s since
> I technically don't use a device I've defined.
>
> It'd be much much better if I could do something like this in my services:
>
>   (devices (list (file-system
>                    (uses '("/dev/matrix/root"))
>                    (creates '("/"))
>                    (device "/dev/matrix/root")
>                    (mount-point "/")
>                    (type "ext4"))
>                  (swap-device
>                    (uses '("/dev/mapper/matrix-swap"))
>                    (creates '()))
>                    (device "/dev/mapper/matrix-swap")
>                  (lvm-device
>                    (uses '("/dev/mapper/hdd" "/dev/sdb"))
>                    (creates '("/dev/matrix/"
>                               "/dev/mapper/matrix-swap"))
>                    (devices '("/dev/mapper/hdd" "/dev/sdb")))
>                  (luks-device
>                    (uses '("UUID=3D4dab5feb-d176-45de-b287-9b0a6e4c01cb"))
>                    (creates '("/dev/mapper/hdd"))
>                    (device "UUID=3D4dab5feb-d176-45de-b287-9b0a6e4c01cb")
>                    (name "hdd")
>                    (key-file "..."))))
>
> The issue is that it has a lot of duplicate information as I'm not sure
> uses/creates could always map to device/mount-point, like LUKS names. But=
 this
> should satisfy most dependency issues automatically, I hope.

There are several issues being addressed here, IIUC:

  1. How to refer to block devices (in the Unix sense) using UUIDs,
     labels, or /dev file names in general, and not just for
     =E2=80=98file-system=E2=80=99.

  2. How to determine dependencies among all these things.

  3. How to handle mapped devices that lead to several /dev nodes, as is
     the case with LVM.

For #1, I would like to have a general =E2=80=98device=E2=80=99 type, so on=
e could
write:

  (operating-system
    ;; =E2=80=A6
    (file-systems (list (file-system
                          (source (device (title 'label)
                                          (name "my-root")))
                          (mount-point "/"))))
    (swap (list (device
                  (title 'uuid)
                  (name (uuid "4dab5feb-d176-45de-b287-9b0a6e4c01cb")))))

For that to work, we ideally need code to recognize swap signatures,
similar to what we do for ext2 in (gnu build file-systems).

For #3, what about changing the =E2=80=98target=E2=80=99 field of =E2=80=98=
mapped-device=E2=80=99 such
that it can be a list of /dev file names?

For #2, I=E2=80=99m not sure we need to change anything, but let=E2=80=99s =
discuss it
later.  :-)

Ludo=E2=80=99.