GNU bug report logs - #31889
Filesystems must not depend on device mappings?

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Taylan Ulrich Bayırlı/Kammer
 <taylanbayirli <at> gmail.com>
Subject: bug#31889: closed (Re: bug#31889: Filesystems must not depend on
 device mappings?)
Date: Thu, 21 Jun 2018 21:56:02 +0000

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Your bug report

#31889: Filesystems must not depend on device mappings?

which was filed against the guix package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 31889 <at> debbugs.gnu.org.

-- 
31889: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=31889
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: ludo <at> gnu.org (Ludovic Courtès)
To: Taylan Kammer <taylanbayirli <at> gmail.com>
Cc: 31889-done <at> debbugs.gnu.org
Subject: Re: bug#31889: Filesystems must not depend on device mappings?
Date: Thu, 21 Jun 2018 23:55:27 +0200

Hi,

Taylan Kammer <taylanbayirli <at> gmail.com> skribis:

>      (mapped-devices
>       (list (mapped-device
>              (source (uuid "b3d059f8-1c4f-4569-88dd-5485825b4373"))
>              (target "guixsd")
>              (type luks-device-mapping))
>             (mapped-device
>              (source (uuid "550d9258-bbbb-488c-af27-6b1fefa190ee"))
>              (target "home")
>              (type luks-device-mapping))))
>      
>      (file-systems
>       (append
>        (list (file-system
>               (device "/dev/mapper/guixsd")
>               (mount-point "/")
>               (type "ext4")
>               (dependencies mapped-devices))
>              (file-system
>               (device "/dev/mapper/home")
>               (mount-point "/home")
>               (type "ext4")
>               (dependencies mapped-devices)))
>        %base-file-systems))

[...]

> It results in the error message:
>
>     guix system: error: service 'file-system-/home' requires
>     'device-mapping-home', which is not provided by any service

[...]

> It works when both '(dependencies mapped-devices)' clauses are simply
> removed.

Yes, it’s “expected”: using “/dev/mapper/xyz” as the device is enough to
express the dependency.

When passing (dependencies mapped-devices), the effect was to each file
system depend on *both* mapped devices.  This leads to an inconsistency
because /dev/mapper/guixsd is “needed-for-boot” (i.e., set up from the
initrd), whereas /dev/mapper/home is not (i.e., set up as a Shepherd
service.)

The solution is to either use the /dev/mapper/xyz names in the ‘device’
field, or to specify only the relevant mapped device in ‘dependencies’.

Anyway, commit 68a58775e071d4b0e000b93ad121b6e64d161b79 fixes it by
doing exactly what this config asks for: setting up all the mapped
devices in the initrd.

Thanks,
Ludo’.

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From: Taylan Ulrich Bayırlı/Kammer
 <taylanbayirli <at> gmail.com>
To: bug-guix <at> gnu.org
Subject: Filesystems must not depend on device mappings?
Date: Mon, 18 Jun 2018 23:11:54 +0200

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If in my OS config I define some luks mappings, and define the
corresponding filesystems with dependencies on the mapped devices,
I get an error on 'guix system reconfigure'.

Example:

  (operating-system
    ...
    (mapped-devices
      (list (mapped-device ... (target "root"))))
    (file-systems
      (list (file-system (mount-point "/")
                         ...
                         (dependencies mapped-devices))))
    ...)

This will yield an error like:

  file-system-/ depends on device-mapping-root, which is not
  provided by any service

Funnily enough, one only needs to remove the 'dependencies' field to
make it work.  But this contradicts the example at:

https://www.gnu.org/software/guix/manual/html_node/Using-the-Configuration-System.html


Taylan

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