[dm-crypt] Are /dev objects required for clean shutdown?

Arno Wagner arno at wagner.name
Tue Feb 6 17:15:12 CET 2018

Hi Pascal,

from my experience copying Linux (Debian) installations,
you statically need /dev/console and /dev/null, everything
else will be created automatically. The static device files
will canish when the devfs is mounted on /dev/ and recreated
as well. But they seem to be needed before that happens
or booting hangs.

For Debian, these can be generated with (after umounting the
dev-fs or from a resuce system):

   cd /dev 
   mknod -m 660 console c 5 1
   mknod -m 660 null c 1 3

Incidentally, cryptsetup should not need a clean shutdown,
but the filesystem in there may like one. Although Linux
filesystems are generally very tolerant of surprising
shutdowns. Probably an effect of PC hardware historically
not being very reliable.


On Tue, Feb 06, 2018 at 16:48:06 CET, Pascal wrote:
> /dev on my CentOS 7 box took a 'rm -rf' yesterday, wiping out most of it.
> Easiest way to recover is to reboot (/dev is on a ramdrive and created from
> scratch during boot), but I'm worried about not getting a clean shutdown.
> Does cryptsetup need anything in /dev to shutdown cleanly?  If so, how do I
> recreate the devices?  The complete list of what is missing from /dev is
> huge, but the below all seem to be disk related and are all gone now:
> /dev/dm-0
> /dev/dm-1
> /dev/dm-2
> /dev/sdb
> /dev/sdc
> /dev/sdd
> /dev/sg0
> /dev/sg1
> /dev/sg2
> /dev/mapper/luks-27bc6c3f-3479-4c65-b2f8-17d35081bbf4
> /dev/mapper/luks-2f41b83f-925d-42f0-aca2-b91b1c6265b0
> /dev/mapper/luks-68f22741-5399-41e5-b40b-81230cb51b27
> _______________________________________________
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> dm-crypt at saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt

Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
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