CentOS - Aug 2014 - Copy on write loop block driver

I am running on the Centos 6.5 x86_64 boot disk.

# uname -a
Linux localhost.localdomain 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC
2013 x86_64 x86_64 x86_64 GNU/Linux

I have been running ddrescue for a while and now it is time to check the
progress.

I want to take the oldhd.img output from ddrescue and load it to satrt
performing recovery (LVM, then filesystem) but I want to do a copy on write with
that.

I fetched
http://www.atcomputing.nl/Tools/cowloop/packages/cowloop-3.2.0.1.tar.gz, built
it

root at localhost ~/cowloop-3.2.0.1
# cowdev -a /root/oldhd.img /root/oldhd.cow
Cannot open /dev/cow/ctl: No such device or address

So I:

root at localhost /dev
# mkdir cow

root at localhost /dev
# cd cow/

root at localhost /dev/cow
# mknod /dev/cow/ctl b 241 255

But I still get a 

root at localhost ~
# cowdev -a /root/oldhd.img /root/oldhd.cow
Cannot open /dev/cow/ctl: No such device or address

Listing /proc/devices I do not see 241.

What am I doing wrong here?

-Jason

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- Jason Pyeron                      PD Inc. http://www.pdinc.us -
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This message is copyright PD Inc, subject to license 20080407P00.

On 8/26/2014 5:03 PM, Jason Pyeron wrote:
> What am I doing wrong here?
A) you don't create anything in /dev, the driver should be using devfs 
to create its own devnodes on the fly as needed.

B) you apparently never loaded the driver.     see 
http://www.atcomputing.nl/Tools/cowloop/loadunload.html



-- 
john r pierce                                      37N 122W
somewhere on the middle of the left coast