One problem and one question to xen 1. I can''t create a domU. This following error I get. Once it seemed that domU was started because xm list was showing etch03 running but xm console etch03 points to an error and etch03 crashed. server1:/vd# xm create -c etch03.cfg Using config file "/etc/xen/etch03.cfg". Error: Device 771 (vbd) could not be connected. Backend device not found. --- title Xen 3.0.3-1-i386 / Debian GNU/Linux, kernel 2.6.18-5-xen-686 root (hd0,0) kernel /xen-3.0.3-1-i386-pae.gz module /vmlinuz-2.6.18-5-xen-686 root=/dev/md1 ro xencons=off console=tty0 module /initrd.img-2.6.18-5-xen-686 savedefault --- ... kernel = "/boot/vmlinuz-2.6.18-5-xen-686" ramdisk = "/boot/initrd.img-2.6.18-5-xen-686" disk = [''file:/vd/etch03.vd,hda3,w'',''file:/vd/etch03.sd,hda2,w''] ... 2. I''m also not sure if I should use xen-3.0.3-1-i386.gz instead of xen-3.0.3-1-i386-pae.gz, but xen-3.0.3-1-i386-pae.gz boots the dom0 and xen-3.0.3-1-i386.gz does''nt. The maschine has only 512 MB RAM so I think its not nessesary to use xen-3.0.3-1-i386-pae.gz. Does it makes a big differens to use xen-3.0.3-1-i386-pae.gz instead of xen-3.0.3-1-i386.gz if this case? _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> 2. > I''m also not sure if I should use xen-3.0.3-1-i386.gz instead of > xen-3.0.3-1-i386-pae.gz, but xen-3.0.3-1-i386-pae.gz boots the dom0 and > xen-3.0.3-1-i386.gz does''nt. The maschine has only 512 MB RAM so I think > its not nessesary to use xen-3.0.3-1-i386-pae.gz. Does it makes a big > differens to use xen-3.0.3-1-i386-pae.gz instead of xen-3.0.3-1-i386.gz > if this case?It depends on your kernel, if your kernel has been compiled with PAE support you have to use the PAE hypervisor, even if you don''t have more than 4G RAM. Mehdi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson
2007-Aug-31 14:51 UTC
Re: [Xen-users] Error: ... Backend device not found.
> I can''t create a domU. This following error I get. Once it seemed that > domU was started because xm list was showing etch03 running but xm > console etch03 points to an error and etch03 crashed. > > server1:/vd# xm create -c etch03.cfg > Using config file "/etc/xen/etch03.cfg". > Error: Device 771 (vbd) could not be connected. Backend device not found. > > --- > title Xen 3.0.3-1-i386 / Debian GNU/Linux, kernel > 2.6.18-5-xen-686 root (hd0,0) > kernel /xen-3.0.3-1-i386-pae.gz > module /vmlinuz-2.6.18-5-xen-686 root=/dev/md1 ro xencons=off > console=tty0 > module /initrd.img-2.6.18-5-xen-686 > savedefault > --- > > ... > kernel = "/boot/vmlinuz-2.6.18-5-xen-686" > ramdisk = "/boot/initrd.img-2.6.18-5-xen-686" > > disk = [''file:/vd/etch03.vd,hda3,w'',''file:/vd/etch03.sd,hda2,w''] > ...Are you sure that both these files exist at the path you''ve stated?> 2. > I''m also not sure if I should use xen-3.0.3-1-i386.gz instead of > xen-3.0.3-1-i386-pae.gz, but xen-3.0.3-1-i386-pae.gz boots the dom0 and > xen-3.0.3-1-i386.gz does''nt. The maschine has only 512 MB RAM so I think > its not nessesary to use xen-3.0.3-1-i386-pae.gz. Does it makes a big > differens to use xen-3.0.3-1-i386-pae.gz instead of xen-3.0.3-1-i386.gz > if this case?The PAE setting of Xen needs to match the PAE setting of the dom0 kernel. If they''re not matched, then dom0 will not boot. PAE may have a slight performance and memory usage penalty, but I doubt it would be significant. The performance difference may not even be measurable for your workloads. The memory usage difference should not be very big (the pagetables are bigger under PAE so they take up more space). An advantage of using PAE is that RedHat seem to have standardised on it for their Xenified kernels, so it would make it easier to run Fedora and RHEL domUs. Some of the other Xen OS ports (e.g. NetBSD, Plan 9) don''t run on PAE, although you could still always install them using HVM mode. Cheers, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> I can''t create a domU. This following error I get. Once it seemed that> > domU was started because xm list was showing etch03 running but xm > > console etch03 points to an error and etch03 crashed. > > > > server1:/vd# xm create -c etch03.cfg > > Using config file "/etc/xen/etch03.cfg". > > Error: Device 771 (vbd) could not be connected. Backend device not found. > > > > --- > > title Xen 3.0.3-1-i386 / Debian GNU/Linux, kernel > > 2.6.18-5-xen-686 root (hd0,0) > > kernel /xen-3.0.3-1-i386-pae.gz > > module /vmlinuz-2.6.18-5-xen-686 root=/dev/md1 ro xencons=off > > console=tty0 > > module /initrd.img-2.6.18-5-xen-686 > > savedefault > > --- > > > > ... > > kernel = "/boot/vmlinuz-2.6.18-5-xen-686" > > ramdisk = "/boot/initrd.img-2.6.18-5-xen-686" > > > > disk = [''file:/vd/etch03.vd,hda3,w'',''file:/vd/etch03.sd,hda2,w''] > > ... >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. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
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 _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson
2007-Aug-31 21:44 UTC
Re: [Xen-users] Error: ... Backend device not found.
> 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.Or, if this is the problem, you could switch to using tap:aio: instead of file:, since that avoids needing the loop devices altogether. e.g. disk = [''tap:aio:/vd/etch03.vd,hda3,w'',''tap:aio:/vd/etch03.sd,hda2,w''] Cheers, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
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@4lin.net] > Sent: Friday, August 31, 2007 2:22 PM > To: ''xen-users@lists.xensource.com'' > 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 > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson schrieb:>> 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. > > Or, if this is the problem, you could switch to using tap:aio: instead of > file:, since that avoids needing the loop devices altogether. > > e.g. > > disk = [''tap:aio:/vd/etch03.vd,hda3,w'',''tap:aio:/vd/etch03.sd,hda2,w''] > > Cheers, > Mark > >That was it, too many loop mounts and and an error in /etc/xen/xend-config.sxp. The error in xend-config.sxp was there only because some debian scripts configured it new what I did''nt reconised ... :-(( Many thanks for your hints. Frank _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Nico Kadel-Garcia
2007-Sep-01 10:32 UTC
Re: [Xen-users] Error: ... Backend device not found.
David Morris wrote:> 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. >virt-manager of RHEL 5 is already sadly out of date. If you grab and recompile the one from Fedora 7, it seems to be a good update and more usable. Or use virt-install, that has better logging and some options not in virt-manager. Then use virt-manager if necessary to access the console. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users