[dm-devel] how to create /dev/mapper/control?

[Kevin Corry]

On Thursday 24 June 2004 4:53 am, Ling, Xiaofeng wrote:
> I download and install device-mapper,
> but when I run dmsetup info, it says /dev/mapper/control open failed.
> So how should I create the device node? what major & minor?
> I tried 253,0, still fail.

In the device-mapper source package, there's a script called 
scripts/devmap_mknod.sh that you can run from your boot-scripts to 
create /dev/mapper/control each time you boot.

In practice, I've always seen /dev/mapper/control with dev-number 10:63. But 
this isn't guaranteed. The control node is registered with the "misc" 
character driver, and simply asks for the first available minor number under 
that driver. This means you need to first grep /proc/devices for "misc" to 
get the major number, then grep /proc/misc for "device-mapper" to get the 
minor number. This is basically what the above script does.

-- 
Kevin Corry
kevcorry at us.ibm.com
http://evms.sourceforge.net/