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RE: [Xen-users] Error: ... Backend device not found.


  • To: <xen-users@xxxxxxxxxxxxxxxxxxx>
  • From: "David Morris" <david.morris@xxxxxxxxxx>
  • Date: Fri, 31 Aug 2007 14:51:04 -0700
  • Delivery-date: Fri, 31 Aug 2007 14:51:45 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcfsFRf0sOJZWGMXQPOltwgnpx5HUgAAa10w
  • Thread-topic: [Xen-users] Error: ... Backend device not found.

Couple additional suggestions 
a. From your grub data, it appears you are using software raid on the dom0 ... 
might be that
   your configured devices need to be mdX devices to match your kernel, etc.
b. you may need a 'root=/dev/hda2 rw' or some such in your config if it isn't 
there
c. it appears from the config fragment that this is a paravirt installation?

This sounds like a problem I encountered when I tried to use virt-manager to 
create a paravirt RHEL5 domU on RHEL5 dom0. I've fought so many alligators over 
the past week that I'm not sure I found a solution or a way around it ....

I think I concluded that there was a fundamental disconnect between the 
virt-manager PV setup and reality ... what I did that worked:
  a. with virt-manager, create an HVM guest (it worked)
  b. upgrade to Xen 3.1 
  c. follow the steps in my post of last night to clone the HVM guest as a para 
virt guest

btw ... you can check the number of loop devices in use with the 'losetup -a' 
command. When I had my difficulties, I was using lvm devices so loop devices 
was not the issue.

> -----Original Message-----
> From: Denny Schierz [mailto:linuxmail@xxxxxxxx]
> Sent: Friday, August 31, 2007 2:22 PM
> To: 'xen-users@xxxxxxxxxxxxxxxxxxx'
> Subject: Re: [Xen-users] Error: ... Backend device not found.
> 
> 
> hi,
> 
> Frank schrieb:
> 
> >>Are you sure that both these files exist at the path you've stated?
> > 
> > Yes, the pathes are right. I nearly get sick. I've checked 
> it several
> > times and again and again :
> >> > Error: Device 771 (vbd) could not be connected. Backend 
> device not
> > found.
> 
> maybe too many loop mounts? Try to create a few new loop devices.
> 
> --
> 
> modules.conf:
> 
> options loop max_loop=256
> 
> # mknod -m 660 /dev/loop8 b 7 8
> # mknod -m 660 /dev/loop9 b 7 9
> # mknod -m 660 /dev/loop10 b 7 10
> 
> or just:
> 
> # for ((i=8;i<=$ANZAHL;i+=1)); do mknod -m 660 /dev/loop$i b 
> 7 $i; done
> 
> 
> # if loop is compiled into the kernel, than you have to add 
> to the Linux
>  Kernel line:
> 
> module /boot/vmlinuz max_loop=256 ....
> 
> cu denny
> 
> -- 
> Stoppt den Überwachungswahn - Stoppt den Schäuble Katalog:
> http://www.nopsis.de
> 
> 

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