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Re: [CentOS-virt] Domain0 with Kernel 2.6.18-92.1.22.el5xen fails to boot Guests with Kernel 2.6.18-164.el5xen
by Christopher G. Stach II 27 Sep '09

27 Sep '09

----- "Devraj Mukherjee" <devraj(a)gmail.com> wrote: > Hi all, > > I am in a bit of a fix here, I have several Guests paravirtualized > running on a Dom0 that is currently running the 2.6.18-92.1.22.el5xen > Kernel. All my guests (administered by different people) have > subsequently been updated to later versions of the kernel (namely > 2.6.18-164.el5xen or 2.6.18-128.4.1.el5xen). [...] > I restarted a Guest that's now trying to boot with the > 2.6.18-164.el5xen Kernel and it spits out messages like > XENBUS: Waiting for devices to initialise: 295s...290s... > > and eventually reboots. IIRC, there were changes to the block back-/frontend drivers a while back, but that probably wouldn't do this. I would first look to make sure that your dom0 Xen daemons are in good condition. Occasionally, they will die or stop working. Watching the logs when you start your guest may give you some clues as to what dom0 may be hanging on. Restarting xend and/or xenconsoled (typically when your guest can't get a console or when ``xm console'' mysteriously doesn't work) may help. Anyway, you should update your dom0 kernel. That's pretty old. :) -- Christopher G. Stach II

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xen & iSCSI
by Daniel De Marco 24 Sep '09

24 Sep '09

Hi, I'm setting up xen (on centos 5.3) and I'm facing a weird performance issue with iSCSI. I attach the iSCSI targets to dom0 and if I use them from dom0 I obtain good performance with simple dd tests (~100MB/s both reading and writing). I then use the block devices for the domU and if I repeat the same dd test from within the domU the write performace is still good (~100MB/s), but the read performance is cut in half (~55MB/s). I tried changing several parameters like read_ahead and such, but I can not obtain a good read performance in the domU. Any idea? Thanks, Daniel.

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Writing iptables for inbound connections with libvirt
by carlopmart 16 Sep '09

16 Sep '09

Hi all, I have installed a CentOS 5.3 x86_64 server with kvm and libvirt to do some tests for future virtualized deployments. My environment: eth0 --> 172.25.50.1/24 ("public" host ip) virbr0 ---> 192.168.122.1/24 (natted interface installed by libvirt) virbr1 ---> 172.26.50.0/24 (internal virtualized network, whithout physical interface binded) Between 192.168.122.0/24 network and 172.26.50.0/24 network I have installed a virtual firewall. So to reach 172.26.50.0/24 network, all connections needs to come from 192.168.122.0/24 network. I need to insert some iptables rules to allow access to some services installed on 172.26.50.0/24 network like smtp,http,ftp, etc. How can I configure libvirt to forward and nat these services coming from 172.25.50.0/24 network to a specific IP under 192.168.122.0/24 network?? Or do I need to use /etc/sysconfig/iptables configuration?? Some examples, please??. Many thanks. -- CL Martinez carlopmart {at} gmail {d0t} com

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Fenker, Oliver is out of the office.
by oliver.fenker＠bayerbbs.com 15 Sep '09

15 Sep '09

Ich werde ab 12.09.2009 nicht im Büro sein. Ich kehre zurück am 25.09.2009. I will be out of the office starting 2009-09-12 and will not return until 2009-09-25

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kvm and related packages
by Farkas Levente 09 Sep '09

09 Sep '09

hi, as 5.4 was released and it's include support for kvm (what's more it's working for us since a few days) i plan to remove all of my packages form my repos as centos 5.4 will be released: http://www.lfarkas.org/linux/packages/centos/5/*/virt/ there are few trick although eg in the xml conf files you have to replace /usr/bin/qemu-kvm to /usr/libexec/qemu-kvm. and it's better it you first remove all of your current kvm related packages install the new kernel, reboot, remove the old kernel and only after intall the new packages (otherwise you've got a lot's off error and warning about weak-updates).. ps. we finish rhel 5.4 rebuild at the weekend:-) there are a few tricks, some of them have to modify to rebuild like etherboot or build with special option like zsh, kvm, *kmod etc. -- Levente "Si vis pacem para bellum!"

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Cluster failover
by Paras pradhan 01 Sep '09

01 Sep '09

hi, I have 3 nodes of CentOS 5.3 running xen virtual machines as virtual machine service. This cluster is working fine. One thing I would like to know that how to make failover only to third node. What I mean to say is: I have 3 virtual machine running on node 1 and 2 virtual machines running on node 2. Now if node 1 fails I want my the node1 virtual machines to be stared only on node 3 but not on node2. Similary if node2 breaks, I want virtual machines to be started on node3 but never on node 1. Thanks ! Paras.

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Migrate windows VM from i386 Host to x86_64 host
by James Roman 01 Sep '09

01 Sep '09

Somehow one of our Xen servers ended up loaded with the i686 xen kernel, instead of the x86_64. The host has one windows VM running on it. The OS partition is file-based, but it also has a logical volume partition assigned for data. We would like to migrate the host server to a 64-bit kernel, which means moving the VM to one of our other 64-bit host servers. We tried simply copying the OS partition and using dd to move the LVM partition to a new host unsuccessfully. I'm pretty sure that dd may not be appropriate when moving between kernel architectures. However, even without the LVM partition specified in the vm config file, we are unable to boot the windows system. It looks like it is blue screening immediately, since we never get a console connection. Are there any instructions anywhere for moving VMs from one host architecture to another? Current Host: Centos 5.3 i686 kernel 2.6.18-128.2.1.el5 Xen 3.0.3-80.el5_3.3 Destination Host: Centos 5.3 x86_64 kernel 2.6.18-128.2.1.el5 Xen 3.0.3-80.el5_3.3

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domU reboot leaves VM crashing continually
by Robert E. Moser 01 Sep '09

01 Sep '09

Greetings, Im new to xen virtualization on CentOS, but I have been unable to find the answer to this problem Im experiencing. My setup: AMD quad core (64bit), 8Gb ram. CentOS 5.3 dom0, CentOS 5.3 domUs (paravirtualized). Dom0 is set up with two NICs, the built-in and a PCI card, and I set up xen bridging on both interfaces. My domUs seem to boot up fine, run fine, and shutdown fine. However, if I attempt a reboot operation, they go into a state where they continually crash on startup. I have been unable to ascertain why this happens, and I do not know how to fix it when it does happen. So, my question is twofold: 1) How do I get it out of the continual boot/crash cycle? Xm destroy doesnt work, none of the GUI tools work. So far the only answer has been rebooting dom0, which is not a good answer L 2) Has anyone else seen this/solved this? Besides being able to manually fix it from #1 above, it sure would be nice to have it able to reboot as expected. I havent worked with any fully virtualized guests yet, but I will try that pretty soon and see if it evidences the same behavior. Uname a è Linux prathis.localdomain 2.6.18-128.7.1.el5xen #1 SMP Mon Aug 24 09:14:33 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux Please let me know what additional information would be helpful or what I can do to facilitate debugging this issue. Thanks!

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Performance tunning CentOS / Xen
by Ryan Chan 24 Aug '09

24 Aug '09

Hello, I have followed standard documents to install CentOS 5.3 & Xen. After playing around, stuffs are OK. So I move forward to tune the performance, are there any recommended documents/tutorial that specialized on performance tuning VM host/guest, on CentOS / Xen architecture? Thanks

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virtio
by Kanwar Ranbir Sandhu 24 Aug '09

24 Aug '09

Hello Everyone, Can I use virtio modules for network and block devices in CentOS 5.3 VMs when using the KVM packages from the "lfarkas" repo? I've tried change an existing VM to virtio for disk and network, but each time I start it, I get this error: error: Failed to start domain popdns02 error: internal error unsupported disk type 'vda' I don't know why this is happening. From what I've read, virtio should be available. Can someone please tell me what I'm doing wrong? Regards, Ranbir -- Kanwar Ranbir Sandhu Linux 2.6.27.29-170.2.78.fc10.x86_64 x86_64 GNU/Linux 11:32:58 up 6 days, 12:29, 4 users, load average: 0.26, 0.21, 0.33

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