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Autore: Didier Kryn
Data:  
To: dng
Oggetto: Re: [DNG] I have a question about libsystemd0 in devuan ascii,
Le 29/06/2017 à 14:51, karl@??? a écrit :
> Didier:
>> Le 26/06/2017 à 23:57, Steve Litt a écrit :
>>> On Mon, 26 Jun 2017 12:25:40 +0200
>>> Didier Kryn <kryn@???> wrote:
>>>>        mdev is fine for a server. It is lacking a few features w/r udev:

>>>>
>>>>        1) It doesn't build /dev/disk/[by-id | by-label | by-partuuid |
>>>> by-path | by-uuid]

>>>>
>>>>            I tried to add this feature by the mean an mdev-called
>>>> script ~ a year ago in a Busybox OS, and succeeded easily with
>>>> by-label and by-uuid. I don't know the usage of the others anyway.
>>> Could you please post that shellscript and a couple sentences about how
>>> to install it?

>>>
>>       Please find it in attachment. The archive contains four files:

>>
>> README
>> etc/init.d/mdev  -- The start/stop script for Sysvinit
>> etc/mdev.conf    -- The necessary configuration file for mdev
>> sbin/mdev-disk   -- An experimental script to manage /dev/disk/by-label
>>                    -- and /dev/disk/by-uuid

>>
>>       I might restart experimenting with it some day...
> Hmm, something similar could be used to create thoose /dev/disk/by-*,
> for a static /dev:

>
> find /dev -type b | xargs blkid | sort | some_script_to_populate_by_xxx
>
> But if that is only a transformed /sys/class/block, wouldn't it be
> easier if there was a /sys/class/uuid or similar ?
>
> Also man blkid says:
>
> # man blkid | grep -A6 ' -L label$'
>         -L label
>                Look up the device that uses this label (equal to: -l -o  device
>                -t  LABEL=<label>).   This lookup method is able to reliably use
>                /dev/disk/by-label udev symlinks  (dependent  on  a  setting  in
>                /etc/blkid.conf).   Avoid using the symlinks directly; it is not
>                reliable to use  the  symlinks  without  verification.   The  -L
>                option works on systems with and without udev.

>
> so if /dev/disk/by-* isn't reliable, why do we have them ?
>
> Regards,
> /Karl Hammar
>


    Everybody is using blkid to build thiese links, my script as well as 
Udev and Vdev. You probably noticed that blkid has a special option for 
Udev because Udev people are too lazzy to parse the response. In Vdev, 
Jude made the parsing job to be compatible with Busybox's blkid which 
hasn't this special format.


    So blkid authors on one hand provide a special format for Udev to 
create the symlinks, and on the other hand claim that they aren't reliable!


     Didier