Re: [Xen-users] Error: Device 2049 (vbd) could not be connected. Backend device not found.

[Joe Warren-Meeks <joe.warren-meeks@xxxxxxxxxxxxx>]

On 28 Apr 2006, at 12:32, Abi Chirayil wrote:

> Joe Warren-Meeks wrote:
>
> > On 27 Apr 2006, at 14:43, Joe Warren-Meeks wrote:
> >
> > Hey guys,
> >
> > > > I've installed xen 3 and xen-tools on my ubuntu server and all  
> > > > seems
> > > > well, until I try to start a client domain. (running on Linux
> > > > xenserver 2.6.12.6-xen #1 SMP Wed Feb 1 21:23:17 UTC 2006 i686
> > > > GNU/Linux)
> > > Bit of a follow-up. If I try to start the DomU, it initally  
> > > errors as
> > > so:
> > >
> > > root@xenserver:/etc/xen# xm create -c squid1.cfg
> > > Using config file "squid1.cfg".
> > > Error: Device 2049 (vbd) could not be connected. Backend device not
> > > found.
> > >
> > > and then shows up as paused in 'xm list'
> > >
> > > If I then attach a console to it, then unpause I see the following
> > > error at the end:
> > >
> > > VFS: Cannot open root device "sda1" or unknown-block(0,0)
> > > Please append a correct "root=" boot option
> > > Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-
> > > block(0,0)
> > >
> > > I've tried adding /dev/ nodes using MAKEDEV in both the Dom0 and  
> > > DomU
> > > and tried changing sda to hda, to no avail.
> > >
> > > Anyone got a pointer to where I can start looking?
> > As a futher follow up, if I use xen-create-image to create a new  
> > domU,
> > this completes fine and then starts the image successfully! I can  
> > then
> > go and start all the other images and all is fine.
> >
> > Once I've halted them all and rebooted the server itself, it all  
> > stops
> > working again.
> >
> > Anyone got any pointers? This is getting quite frustrating.
> I'm getting exactly the same error (also using Ubuntu). I just tried
> mounting and unmounting the one of the images and that seems to get
> everything working - till the next reboot.
>
> mount -o loop /vserver/images/vmNMS.img /vserver/vm_base/
> umount /vserver/vm_base/
>
> Any idea why this happens? I've also been pulling my hair out the past
> couple of days.
Think I've fixed it.

I read xen-create-image to see why it seemed to work if I used that.  
Just by an aside I noticed that there is an option of use-ide
So, I've set "use-ide = 1" in /etc/xen-tools/xen-tools.conf and  
recreated my images and it seems to work now.
I figure that an IDE server has problems trying to run a SCSI domU

I'm creating a bunch of domUs now and rebooting to see if they all  
start ok. (I also had to up my loopback devices as indicated in  
another post)
Give it a shot and report back.

 -- joe.

Joe Warren-Meeks                       T: +44 (0) 208 962 0007
Aggregator Limited                     M: +44 (0) 7789 176078
Unit 62/63 Pall Mall Deposit           E: joe.warren-meeks@xxxxxxxxxxxxx
124-128 Barlby Road, London W10 6BL
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