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Re: [Xen-users] Device 2049 (vbd) could not be connected. Backenddevice

To: Brian Lavender <brian@xxxxxxxxxxxxx>
Subject: Re: [Xen-users] Device 2049 (vbd) could not be connected. Backenddevice not found.
From: Borja Sotomayor <borja@xxxxxxxxxxxx>
Date: Thu, 15 Dec 2005 15:18:37 -0600
Cc: Satoshi Uchida <s-uchida@xxxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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When the domain fails, try this.

for i in /dev/loop*
losetup $i

If you don't have any VM's running, and you see a loopback device
connected, it could be that somewhere in Xen (I believe xenstored) is
not releasing the losetup connection to the image file. I have seen some
problems with this in testing. You can manually delete the connection

My problem was different, because there were loopback devices that weren't being connected at all when creating a new domain. However, you did nudge me in the right direction. losetup revealed that my system has 16 /dev/loop's (loop0...loop15), but the kernel only supports the default 8. When creating the domain, Xen correctly connected to loop0 and loop1, but when checking for the "next available loop device", Xen picked loop10 (instead of loop2), which resulted in the error. Setting max_loop to 16 solved my problems :-) Thanks!

Borja Sotomayor, University of Chicago
 Ph.D. Student, Department of Computer Science
 Hinds 016, 5734 South Ellis Avenue, 60637 Chicago, IL
GT4 Tutorial: http://gdp.globus.org/gt4-tutorial/
BorjaNet:  http://www.borjanet.com/   borja@xxxxxxxxxxxx
         "Dis maschine vill run und run!"
               -- Kurt Gödel (on the Turing Machine)

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