[dm-crypt] renaming of device

Arno Wagner arno at wagner.name
Sat Jan 16 17:22:30 CET 2010


On Sat, Jan 16, 2010 at 09:39:58AM +0100, Milan Broz wrote:
> On 01/16/2010 03:46 AM, Arno Wagner wrote:
> > It does. Each possible /dev/sd<x> has a defined, fixed 
> > major/minor, see Documentation/devices.txt in a Linux kernel 
> > source tree.
> 
> so long thread:-)
> 
> Well, the situation is more complicated.
> 
> If cryptsetup uses only "real" block devices (like /dev/sdaX),
> then fix to display proper device is is trivial.
> (Parsing is in cryptsetup internal, not system libdevmapper currently.)
> 
> But if you have stacked devices "virtual block devices"
> (crypt over MD or over LVM) it can be different - you want to see
> /dev/VG/LV as device, not /dev/dm-X.
> 
> (btw dm-X names are not persistent and were intended to be kernel internal
> only, unfortunately now are visible in userspace because of unified
> udev event processing. And renaming these nodes to me more user-frientdly
> in kernel is not easy because of various name length limits and different
> approach for renaming of active DM devices) 
> 
> But the real problem now is that device-mapper library is just
> in process of transition to udev (all nodes and symlinks will be created
> by udev and not internally in libdevmapper).
> And this changed (unified) some nodes to symlinks and vice versa.
> 
> With various maintainer's udev rules in various ditributions it creates nice
> mix and Debian usually modifies even default rules for dm devices.
> 
> (Actually if you have an udev rule, which creates another node and not
> symlink in /dev/scsi/..., it is  probably not correct, it should be symlink.)

I think so too, but I am unable to find it. Maybe I will just 
start to disable udev rules, until the behaviour goes away. 
Then I can file a bug report wth Debian.
 
> Anyway, I'll plan to fix it somehow in next minor release of cryptsetup
> (1.1.1 probably).

Looking forward to find out what your solutin will be ;-)

Arno




 
> Milan
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-- 
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
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