Bug#542422: [linux-lvm] Re: Bug#542422: dmsetup: I would like to have speaking device names back

2009-09-08 Thread Peter Rajnoha
On 08/19/2009 05:15 PM, Bastian Blank wrote:
 On Wed, Aug 19, 2009 at 04:50:09PM +0200, Marc Haber wrote:
 Since the last update, my crypto devices are recognized by the system as
 /dev/dm-xx, for example in fsck and in df's output:
 /dev/dm-15 12G   11G  565M  96% /mnt/home
 /dev/dm-137,9G  7,0G  532M  94% /mnt/usr
 /dev/dm-143,0G  1,4G  1,5G  50% /mnt/var

 lrwxrwxrwx  1 root root  8 19. Aug 09:06 home - ../dm-15
 lrwxrwxrwx  1 root root  8 19. Aug 09:06 usr - ../dm-13
 lrwxrwxrwx  1 root root  8 19. Aug 09:06 var - ../dm-14

 I'd like them to show up as /dev/mapper/home, /dev/mapper/usr and
 /dev/mapper/var again.
 
 This means that the real devices needs to be named this way as mount
 always dereferences symlinks.
 
 Patch which does this against the Debian package is attached.
 
 Alasdair: Does Red Hat solve that problem somehow?
 
 Bastian
 

Just to explain why we decided to do it this way in LVM upstream:

The (very) early version of the rules were discussed with udev team
so it would be correct from udev point of view as well. The discussion
led us to a solution where we had to use /dev/dm-* as nodes and
/dev/mapper/* as symlinks, citing Kay Severs:


In general we do not want any unneeded disconnect from kernel names
and /dev names, and dm block devices should stay as /dev/dm-* device
nodes.

Please do not rename kernel devices, they should match the kernel names.
Only create SYMLINK+= to the kernel names...

(you can find the whole discussion at 
http://markmail.org/message/bj4zkjo2peeocnhq)


We're just trying to comply with those udev requirements...

Yes, there are some problems associated with the utilities using
/dev/mapper nodes, but, as Alasdair says, this should be corrected
there directly. We have no other way, either we break 'udev laws'
or we break a few utilities. But we would like to do this correctly,
so I'm voting for the update of those utilities (the grub2 problem
mentioned somewhere here in this bz -- I'm already preparing
a proposal for the grub team to deal with this issue).

It's quite painful now, I know, but once done correctly and having
all depending things fixed, we will have a proper solution that
everybody will be happy with.

Peter



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Bug#542422: [linux-lvm] Re: Bug#542422: dmsetup: I would like to have speaking device names back

2009-09-07 Thread Alasdair G Kergon
On Wed, Aug 19, 2009 at 05:15:13PM +0200, Bastian Blank wrote:
 Alasdair: Does Red Hat solve that problem somehow?
 
This stuff is about to all change.

Apps with hard-coded naming logic (like mount?) may then need updating.

Alasdair




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