xen June 2008

xen@lists.stg.fedoraproject.org

39 participants
24 discussions

Subject: Re: [Fedora-xen] How to backup a Domu filesystem (on LVM) from Dom0 on Fedora 8 ?
by Henok Mikre 08 Jun '08

08 Jun '08

This helped me a great deal. Thanks. I just have a few questions... 1) is it best to unmount the /mnt/lvfoo/ before or after kpartx -d? because you have it in your procedure list both before and after kpartx -d. 2) is it possible to explore this dump file by either mounting it or some other method? 3) what is the best procedure to replace this dump file in case of a disk failure? i.e. just install xen and use virt-install? 4) is this the best possible method of backing up a domU? Thanks. Gerd Hoffmann wrote: Anne Facq wrote: Because in Dom0 the device for a paravirt Domu (/dev/vg00/lvfoo in my case) is mapped to a virtual disk /dev/xvda (I created the Domu with virt-install), and the only way I found to mount this Domu filesystem, is to : - get the size of the boot sector of /dev/vg00/lvfoo (with fdisk -ul /dev/vg00/lvfoo) = 63 - compute the offset (multiply by block size) - specify this offset to the mount command : mount -o offset=32256 /dev/vg00/lvfoo /mnt/ Uh, oh, quite complicated and error prone. Can be done much easier. Option (1): Use kpartx, it will create device mapper mappings for your partitions. Try "kpartx -v -a /dev/vg00/lvfoo", should give you /dev/vg00/lvfoop[1234]. "kpartx -d ... " removes the mappings. Option (2): (works only with xen kernel): Configure the device as virtual disk *in Domain-0*: "xm block-attach 0 phy:/dev/vg00/lvfoo xvda w". Gives you /dev/xvda[1234]. "xm block-detach ..." removes it. Many thanks for this solution, it helps me a lot. If this can help someone, here are the steps to backup a Domu (filesystem on LVM in backend and on xvda in frontend) with the dump command from Dom0 (Fedora 8), using one of the 2 solutions you advised, kpartx : ---------------------------------------------------------------- # The DomU named "foo" must be stopped before dump xm shutdown -w foo # Creates device mapper mappings /dev/mapper/lvfoop[1234] for /dev/vg00/lvfoo kpartx -v -a /dev/vg00/lvfoo # Mounts temporarly the filesystem to backup mount /dev/mapper/lvfoop1 /mnt/lvfoo/ # Launches the dump /sbin/dump 0 -L FULL_foo -f /BACKUP-XEN/foo.colddump /mnt/lvfoo/ # Umount the filesystem umount /mnt/lvfoo/ # Removes the mappings kpartx -d /dev/vg00/lvfoo # Unmount the filesystem umount /mnt/lvfoo # The DomU can now be restarted xm create --config /var/lib/xend/.... ---------------------------------------------------------------- Regards, Anne Facq

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Compiling xen from source: mkinitrd error: No module ehci-hcd
by Henok Mikre 06 Jun '08

06 Jun '08

Hi, I was trying to compile a xen kernel from source and I am having the following errors: [root@machine xen-3.0.4-testing.hg]# mkinitrd -v -f --with=sd_mod --with=scsi_mod /boot/initrd-2.6.16.38-xen0.img 2.6.16.38-xen0 Creating initramfs Looking for deps of module ehci-hcd No module ehci-hcd found for kernel 2.6.16.38-xen0, aborting. Any thoughts?

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Unable to install domU on Fedora 8
by Pete Kay 04 Jun '08

04 Jun '08

Hi, When trying to install Cent domU on fedora 8 dom0, I am getting the following error. I have tried both graphics support Yes and No [root@bogon pete]# virt-install What is the name of your virtual machine? serverA How much RAM should be allocated (in megabytes)? 256 What would you like to use as the disk (file path)? /dev/serverA Would you like to enable graphics support? (yes or no) no What is the install location? http://mirror.centos.org/centos-5/5/os/x86_64/ Starting install... libvir: Xen Daemon error : GET operation failed: Retrieving file CentOS... 590 kB 00:26 Retrieving file vmlinuz.. 100% |=========================| 1.8 MB 01:10 Retrieving file initrd.im 100% |=========================| 5.2 MB 03:17 libvir: Xen Daemon error : GET operation failed: libvir: Xen Daemon error : POST operation failed: (xend.err 'Device 51712 (vbd) could not be connected. losetup /dev/loop0 /dev/serverA failed') virDomainCreateLinux() failed POST operation failed: (xend.err 'Device 51712 (vbd) could not be connected. losetup /dev/loop0 /dev/serverA failed') Domain installation may not have been successful. If it was, you can restart your domain by running 'virsh start serverA'; otherwise, please restart your installation. Thu, 05 Jun 2008 03:09:50 ERROR virDomainCreateLinux() failed POST operation failed: (xend.err 'Device 51712 (vbd) could not be connected. losetup /dev/loop0 /dev/serverA failed') Traceback (most recent call last): File "/usr/bin/virt-install", line 502, in <module> main() File "/usr/bin/virt-install", line 462, in main dom = guest.start_install(conscb,progresscb) File "/usr/lib/python2.5/site-packages/virtinst/Guest.py", line 813, in start_install return self._do_install(consolecb, meter) File "/usr/lib/python2.5/site-packages/virtinst/Guest.py", line 834, in _do_install self.domain = self.conn.createLinux(install_xml, 0) File "/usr/lib64/python2.5/site-packages/libvirt.py", line 573, in createLinux if ret is None:raise libvirtError('virDomainCreateLinux() failed', conn=self) libvirtError: virDomainCreateLinux() failed POST operation failed: (xend.err 'Device 51712 (vbd) could not be connected. losetup /dev/loop0 /dev/serverA failed') [root@bogon pete]# I would appreciate any help on getting xen to work. Thanks, Pete

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ANNOUNCE: virt-mem: tools for monitoring virtual machines
by Richard W.M. Jones 03 Jun '08

03 Jun '08

I'm pleased to announce this very early pre-alpha release of a further set of tools for monitoring virtual machines. The idea is to provide simple commands which can be run outside the virtual machine to monitor its status. These commands don't require you to log in to the virtual machine, or to install any software, since they work entirely by snooping. So they could be very useful for analyzing guests which are stuck / unresponsive / heavily loaded. Done so far: virt-uname like uname(1), print guest's system information virt-dmesg like dmesg(1), print guest's kernel messages Coming soon: virt-ps like ps(1), lists processes virt-free like free(1), lists free memory and swap If virt-ps works out, I might do a 'top'-like command, although of course I can't call it virt-top. I'm open to other suggestions too. Home page: http://et.redhat.com/~rjones/virt-mem/ Source: http://hg.et.redhat.com/virt/applications/virt-mem--devel ****NOTE**** These require a (forthcoming) patch to libvirt to snoop on virtual machines' memory. At the moment you can run them by using the QEMU memsave command to snapshot kernel memory to a file, and then run the program on the file. The snapshot process is described here: http://felinemenace.org/~andrewg/MikroTik_Router_Security_Analysis_Part2/ Support for Xen is still under investigation, but we believe it should be possible. Example: (qemu) memsave 3222274048 15728640 snap.mem $ virt-uname -A i386 -T i386 -t ~/snap.mem /home/rjones/snap.mem: Linux localhost.localdomain 2.6.24-0.155.rc7.git6.fc9 #1 SMP Tue Jan 15 17:52:31 EST 2008 i686 (none) Rich. -- Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into Xen guests. http://et.redhat.com/~rjones/virt-p2v

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xen June 2008