Hi Arno,
What I was trying to say, I think the current behavior usually should do
a good job, when there is only one device inode (as expected).
Concerning udev - you could either modify the configuration for the scsi
subsystem, or you could copy it to you own rule file modify it and
override debian's defaults.
This ways you are a little safer, when the distribution modifies some
rules (for some odd reason) and are sure that dmcrypt returns the name
you expect. In general this is true for most device names where you have
special needs.
On my debian there are no rules for creating /dev/scsi/* names, at least
not for scsi disks. Might be you are stuck with an older udev or some
outdated configuration maybe?
Regards
-Sven
Arno Wagner schrieb:
Hi Sven,
On Thu, Jan 14, 2010 at 07:18:50PM +0100, Sven Eschenberg wrote:
Hi Arno,
Agreed.
Concerning the actual problem: This should not go into cryptsetup, it's
not the right place.
Well, it is actually already in there, just at the moment it
gives you the first it finds. I think it is acceptable to have
it in there, as cryptsetup already is a frontend. Writing a
frontend for a frontend is a bit redundant.
If we talk convetions, then the convention is:
There is only ONE inode representing the device under /dev. If your
hotplug manager (and it's configuration) creates multiple such entries,
it is an indication for misconfiguration (imho). I.E.: Each device
should have one physical identification (the inode carrying major:minor,
together with the pathname) and as many logical names (via softlinks) as
wanted. This guarantees that the right pathname can be found (not only
for dmcrypt btw) and the device is yet useable via it's symbolic names
(i.e. UUIDs, volume labels etc.).
If the preference of the system administrator is on UUID names, then
those should be created as device files, and the 'traditional names' as
softlinks. If yet there is a need to know all device names that link to
a certain major:minor, then this can and should be done in a simple
shell script, where it belongs in my opinion.
Just my 2 cents
I agree to that. It came when I added udev to my system, which
I do not like, and it creating devices under /dev/scsi/ is the
default under Debian. Clearly this has not been thought through.
As such broken configs can happen and it seems easily, it seems
they need to be expected.
Arno
Regards
-Sven
Arno Wagner schrieb:
Well, I think listing all in /dev/ would be an improvement to
the current behaviour. Of course people can put their device
spceials somewhere else, but that is a pretty big break of
convention that IMO does not need to be supported.
Arno
On Wed, Jan 13, 2010 at 05:18:27PM +0100, Sven Eschenberg wrote:
Hi Arno,
Indeed cryyptsetup traverses /dev stating each file for major:minor
and stops on the first match - at least a trace suggests this. The
question is though, if this is an appropriated approach. One thing
that annoys me when doing this: There's no guarantee that device
inodes are in /dev, nor links to it. In theory it cann be any place
in the filesystem. there can be as many links as you want and as
many inodes for the same device, as you want.
Regards
-Sven
Arno Wagner schrieb:
Having had a bit of time to think about it, it seems that
it would indeed be necessary to store the device name.
A possible alternative is to traverse all of /dev/ and
report all devices that match major/minor. This may be
the solution causing the least effort, as cryptsetup
is doing something like it already, just that it currently
stops after the first match.
In fact, I think I prefer for it to report all devices
that match.
Arno
On Wed, Jan 13, 2010 at 11:20:36AM +0100, Sven Eschenberg wrote:
Hi Luca,
I doubt this is possible. The only possible thing would be: Modify DM,
when a device name is passed in, to keep the passed in name alongside
the actual major:minor and provide an IOCTL, to access the information.
Regards
-Sven
On Wed, 2010-01-13 at 08:01 +0100, Luca Berra wrote:
On Sun, Jan 10, 2010 at 09:33:13PM +0100, Milan Broz wrote:
The algorithm is very simple (and was probably written before
udev was used so these special links in /dev did not exist).
So it need to add some preferred names and not print the first entry.
Please can you add an issue to project pages to not forget about this?
Probably good idea to fix it in next minor release.
it could be useful to have the functionality in device-mapper itself,
instead of duplicating in dm-crypt, lvm, dmraid, whatever ?
Regards,
L.
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