virt March 2010

virt@lists.centos.org

30 participants
22 discussions

RHEL 5.5 Xen fixes
by Pasi Kärkkäinen 15 May '10

15 May '10

Hello, RHEL 5.5 has been released, and it contains many Xen related fixes. Here's the most important of the them.. fixing a dom0 caching bug which could cause domU disk corruption when the domU disk was accessed from dom0 after the domU was shutdown. Most people noticed this bug when pygrub used wrong (cached) information. "pygrub uses cached and eventually outdated grub.conf, kernel and initrd": https://bugzilla.redhat.com/show_bug.cgi?id=466681 And some more: "Xen hypervisor doesn't mask xsave feature from the guest; Fedora 11 PV domU kernel crashes": https://bugzilla.redhat.com/show_bug.cgi?id=524719 "[RHEL-5 Xen]: F-11 Xen 64-bit domU cannot be started with > 2047MB of memory": https://bugzilla.redhat.com/show_bug.cgi?id=502826 " Boot hang when installing HVM DomU": https://bugzilla.redhat.com/show_bug.cgi?id=524052 "[RHEL5 Xen]: PV guest crash on poweroff": https://bugzilla.redhat.com/show_bug.cgi?id=540811 "[RHEL5 Xen]: Cpu frequency scaling is broken on Intel": https://bugzilla.redhat.com/show_bug.cgi?id=553324 RHEL 5.5 kernel changelog: http://rhn.redhat.com/errata/RHSA-2010-0178.html Work-in-progress (Not yet in 5.5): "Grub2 guest support for RHEL5 Xen pygrub": https://bugzilla.redhat.com/show_bug.cgi?id=577511 -- Pasi

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Re: [CentOS-virt] Xen HVM domU won't start since updates to 2.6.18-164.15.1 kernels
by Christopher G. Stach II 12 Apr '10

12 Apr '10

----- "Aaron Clark" <ophidian(a)ophidian.homeip.net> wrote: > qemu: could not open serial device 'none' http://os-drive.com/files/docbook/xen-faq.html#serial_console_hvm Does the LV show that it's open (or ever changes state) when the VM attempts to boot? Did you try taking a snapshot of the LV and mucking around with the xen configuration to see if anything changes? Did you update anything else on the machine, like perhaps the BIOS? Can you mount the VM's filesystem? Is its partition table okay? How about the boot loader? -- Christopher G. Stach II http://ldsys.net/~cgs/

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Re: [CentOS-virt] Xen HVM domU won't start since updates to 2.6.18-164.15.1 kernels
by Christopher G. Stach II 30 Mar '10

30 Mar '10

----- "Aaron Clark" <ophidian(a)ophidian.homeip.net> wrote: > What steps should I take next to debug this? Downgrade back to where you were bit by bit (or just guess that it's dom0's kernel) and see when it starts working again. What does the busted guest say when it tries to boot while you watch its [serial] console? Does the dom0 ever unpause the guest? (It should say in the logs.) -- Christopher G. Stach II http://ldsys.net/~cgs/

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Matthias Lorch ist außer Haus.
by matthias.lorch＠kzvrlp.de 29 Mar '10

29 Mar '10

Ich werde ab 29.03.2010 nicht im Büro sein. Ich kehre zurück am 06.04.2010. Bitte wenden Sie sich in dringenden Fällen an Herrn Roth, 0261 / 9120 - 258 Vielen Dank Gruß M.Lorch

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Xen HVM domU won't start since updates to 2.6.18-164.15.1 kernels
by Aaron Clark 28 Mar '10

28 Mar '10

I have a dom0 machine running CentOS 5.4 with all the latest updates using Xen as my hypervisor. I am using Xen in part because this machine was set up prior to KVM being included in RHEL, and in part because KVM's network bridging configuration is not nearly as simple as Xen's. The dom0 machine is a headless Mac Mini and I do all of my VM management via virsh from the command line. I have two hvm domU's: * A web server running CentOS 5.4 * A mail server running Gentoo Both VM's are backed by LV's on the dom0 but do not use LVM in the domU. Both have virtually identical libvirt configurations (differing by expected things like name, UUID, NIC MAC, VNC port, etc). The web server domU (WSdomU hereafter) does not start since applying the most recent kernel update (kernel-xen-2.6.18-164.15.1.el5.x86_64 and kernel-2.6.18-164.15.1.el5.x86_64 for the dom0 and WSdomU respectively). By 'not start' I mean it appears to be running but it does not use an CPU cycles, does not bring up a graphical console, and does not respond on the network. The WSdomU is listed as no state rather than the normal running or blocked in xentop. The mail server domU starts fine and functions normally. Here are the steps I have taken so far that did not solve the problem: * Reboot the dom0 to see if things come up on their own * Attempted to connect to the WSdomU's graphical (VNC) console from the dom0 * Check xen dmesg on dom0 * Check xend logs (a cursory viewing did not show anything blatant; specific suggestions of things to look for would be appreciated) * Shutdown the mail server domU and attempt to start the WSdomU * Use kpartx to access the partitions of the domU o Tried switching grub to use the previous kernel * Check the SELinux labels on backing LV's (they're the same) * Set SELinux to permissive and attempt to start the WSdomU * Use virsh edit to try tweaking the WSdomU config * virsh undefine, reboot, virsh define the WSdomU config * Use fdisk on the LV to ensure it has the correct partition layout * dd the WSdomU LV to an .img file, copy it to my Fedora desktop and run it under KVM (works fine) * dd the .img file to a new LV and create a new libvirt config xml (fails to start) Sample config used to attempt a reconfiguration: <domain type='xen'> <name>Webserver</name> <os> <type>hvm</type> <loader>/usr/lib/xen/boot/hvmloader</loader> <boot dev='hd'/> </os> <memory>262144</memory> <vcpu>1</vcpu> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <features> <acpi/> <apic/> <pae/> </features> <devices> <emulator>/usr/lib64/xen/bin/qemu-dm</emulator> <interface type='bridge'> <source bridge='xenbr0'/> <script path='vif-bridge'/> </interface> <disk type='block'> <source dev='/dev/mapper/SystemsVG-Webserver'/> <target dev='hda'/> </disk> <graphics type='vnc' /> </devices> </domain> What steps should I take next to debug this? Aaron -- "The goblins are in charge of maintenance? Why not just set it on fire now and call it a day?" --Whip Tongue, Viashino Technician

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PVM Ubuntu and xconsole error with XEN+CentOS
by Fernando Castillo Ortiz 24 Mar '10

24 Mar '10

Hi, I tell you my problem: I've installed a Ubuntu's HVM guest in CentOS with XEN, then I convert my HVM to PVM based in this tutto : http://www.asplund.nu/xencluster/xen-convert-hvm-to-pvm.html After this modification everythings it runs fine but I have a problem with xconsole, I don't see anything when I run the command "xm console ID" , I only see the boot proccess and the last line that I can see it's : * Running local boot scripts (/etc/rc.local) [ OK ] I attached you my config file PS: Sorry for my English -- Fernando Castillo Ortiz Área de Operaciones Emergya Consultoría Tel. +34 951 210 400 +34 663 366 796 Fax. +34 954 51 64 73 http://www.emergya.es

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Silly question about KVM
by Scot P. Floess 18 Mar '10

18 Mar '10

I was wondering, if I do not have hardware that natively supports full virtualization...and I choose to use KVM, will my VMs be running in some form of chip emulation (and therefore terribly slow). To date, I've been using Xen and am very comfortable with it. I have some fears that later whenever Xen is dropped - I'll have to consider KVM. Also, will Xen be carried forward should Xen be dropped from RHEL? -- Scot P. Floess 27 Lake Royale Louisburg, NC 27549 252-478-8087 (Home) 919-890-8117 (Work) Chief Architect JPlate http://sourceforge.net/projects/jplate Chief Architect JavaPIM http://sourceforge.net/projects/javapim Architect Keros http://sourceforge.net/projects/keros

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Re: [CentOS-virt] moving from Xen to KVM
by Christopher G. Stach II 18 Mar '10

18 Mar '10

----- "Dave Augustus" <davea(a)ingraftedsoftware.com> wrote: > I finally realized that when running Xen and in Dom0, Xen hides the > AMD-V in /proc/cpuinfo Really? dom0: flags : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow constant_tsc pni monitor cx16 lahf_lm cmp_legacy svm cr8_legacy guest: flags : fpu tsc msr pae mce cx8 apic mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow constant_tsc pni monitor cx16 lahf_lm cmp_legacy svm cr8_legacy > (...more reasons to move to KVM) I have a hunch that you are going to do whatever you are told to do and that you really have no idea what is going on. Can we get more "Hey, I'm told KVM is cool so I'm migrating all of my production servers to it because the free OS of my choice may not support it in a year or two after I leave my current suckjob position and I hear, since I don't read mainline kernel mailing lists religiously and keep only a superficial idea in my head about kernel development, since I really have no idea what 'kernel development' means, that KVM is the only Jesus-approved way of doing things" threads? None of you seem to have have a head for any of this, it seems. Maybe you're just working for Billy's Interwebs-r-Us and keeping Sally's Nail Shop going strong, but the last time I checked, the "ent" in CentOS stood for "enterprise". Here are a few tips: 1. Fuck KVM. 2. Stick with Xen because there is quite a lot of time until 5 is EOL'd and if you haven't noticed, it's actually a mature technology. 3. Figure out what you are going to do with Sally's Nail Shop in the meantime. If you have time to fuck everything up in your environment with KVM, you can probably save 20% or more optimizing your environment and even more with proper capital investments and training. 4. Figure out how either a) non-critical/enterprise services would ever be served by KVM's features or lack thereof, or b) you are going to CYA when you can't guarantee an SLA. 5. Spend more time on KVM dev lists instead of posting here and annoying others with your butthurt KVM-won't-work posts, as it's not even supported upstream. -- Christopher G. Stach II http://ldsys.net/~cgs/

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What kernel params to use with KVM hosts??
by carlopmart 17 Mar '10

17 Mar '10

Hi all, I order to reach maximum performance on my centos kvm hosts I have use these params: - On /etc/grub.conf: kernel /vmlinuz-2.6.18-164.11.1.el5 ro root=LABEL=/ elevator=deadline quiet - On sysctl.conf # Special network params net.core.rmem_default = 8388608 net.core.wmem_default = 8388608 net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 net.ipv4.tcp_rmem = 1048576 4194304 16777216 net.ipv4.tcp_wmem = 1048576 4194304 16777216 # Disable netfilter on bridges. net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 # Virtual machines special kernel params vm.swappiness = 0 Do I need to configure something more?? Any tips?? Thanks. -- CL Martinez carlopmart {at} gmail {d0t} com

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get xen name from guest
by Ryan Pugatch 17 Mar '10

17 Mar '10

Hello, Is it possible to get the name that was set in a VM's xen config file from the guest machine? I'm interested in having my kickstart launch a script that can configure hostname, but to do that it would need to get the name set in the config. Thanks, Ryan

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virt March 2010