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1612 discussions

Best practices on KVM systems
by Luca Gervasi 12 Jan '13

12 Jan '13

Hello, i'm trying to create some best practices on my centos 6.3 / libvirt /kvm hypervisors. Actually, i use NFS as shared storage backend for every VM and make reasonable use of the KSM (enabling it into qemu.conf). Every VM is configured with VirtIO drivers (when possible) and the disks use none as cacheing method to allow me live migration. I'll be happy to know if there are some more improvements i can implement. Please share your knowledge. Thanks in advance Luca Gervasi

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Andreas Reschke is out of the office
by Andreas Reschke 11 Jan '13

11 Jan '13

Ich werde ab 11.01.2013 nicht im Büro sein. Ich kehre zurück am 21.01.2013.

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mirroring people.centos.org
by Carl T. Miller 07 Jan '13

07 Jan '13

Is there an easy way to mirror people.centos.org? I tried "rsync people.centos.org::" and it gives some disclaimers followed by a null list of available modules. I've got an ugly workaround using wget, but would prefer to use rsync. c -- Carl T. Miller Systems Engineer carl(a)carltm.com

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CentOS AWS AMIs?
by Richard Clark 07 Jan '13

07 Jan '13

Hi list, I've noticed that instance-backed AMIs no longer seem to exist for the 'official' CentOS images, though the EBS ones are fine.. Looking at the wiki (http://wiki.centos.org/Cloud/AWS) the AMIs listed on marketplace are slightly newer than what's listed on the wiki, so just wondering if something got overlooked after the last build? Cheers, -- Richard Clark richard(a)fohnet.co.uk

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Download official CentOS AMI?
by Karl Ward 07 Jan '13

07 Jan '13

I'd like to download the official CentOS AMI files for 6.3 x86_64, but that does not seem possible. The goal is to use the same image on both public and private clouds, to improve consistency. Are the AMI files available for download anywhere, or from anyone? I offer my apologies if the CentOS-virt list is not the correct contact for this query. -- Karl Ward

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Re: [CentOS-virt] Time
by James B. Byrne 02 Jan '13

02 Jan '13

On Wed, January 2, 2013 03:53, Robert Dinse wrote: > > Friday, I moved our servers to a new co-lo facility and ran into > an interesting problem with virtual machines. > > I did an orderly shutdown of the CentOS 6.3 host, and it in > turn suspends all the guests. It took about an hour and a half > to move and fire up the host. > > The guests, being suspended, were then an hour and a half > behind and it seems ntpd does not want to correct more than 1000 > seconds of error so it would not automatically adjust the clocks. > > I tried the -g argument which is supposed to override the > 1000 second limit but it did not. I ended up having to manually > set the clocks close enough for ntpd to correct. > > Since there is no hardware clock for the virtual machines > to use when they boot, it seems that shutdown and reboot of the > virtual machines probably would not have avoided this. > > Any suggestions for addressing this particular scenerio other > than having to manually set a bunch of clocks? > I ran into this situation several times whilst testing KVM and the lessons I learned from the experiences can be summarized as: 1. Never allow the kvm hypervisior to handle guests during a host shutdown. Use 'virsh shutdown' on each of the guests first and then shutdown the host. Use autostart to restart guests on a host's reboot. Write a script to process 'virsh list' to feed active domains to 'virsh shutdown' if automation is required and link that to /etc/rc0.d/K10<whatever>. 2. In the situation where a kvm guest pause and restore sequence leads to an excessive disconnect between guest time and wall time use ntpd -q to hard set the time. From the guest's point of view you are always going ahead in time in the case of a pause and resume so this is not likely to ever cause a problem. But, having written that down, it probably will at some point. 3. Run ntpd on the host system and have its guests configured to only use that time server source. 4. On each guest have a cron job that checks for ntpd at regular intervals which reports failures and restarts the time service as necessary. We use: JOBNAME="Check ntpd status and restart if required" ; \ ntpstat > /dev/null && \ if [[ $? -gt 0 ]]; then /sbin/service ntpd start; fi -- *** E-Mail is NOT a SECURE channel *** James B. Byrne mailto:ByrneJB@Harte-Lyne.ca Harte & Lyne Limited http://www.harte-lyne.ca 9 Brockley Drive vox: +1 905 561 1241 Hamilton, Ontario fax: +1 905 561 0757 Canada L8E 3C3

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root device for CentOS AMI would be /dev/sda1?
by Miida Makoto 25 Dec '12

25 Dec '12

Hi guys, first of all, thanks a lot for all guys preparing for official CentOS AMIs on Amazon Marketplace! However, I have noticed a problem on a swap device when I launch a m1.small instance with the official AMI. AWS prepares two local storages for m1.small and c1.medium; one is for 160GB instance store storage, and the other is for a storage for the swap space, described in: http://docs.amazonwebservices.com/AWSEC2/latest/UserGuide/InstanceStorage.h… I assume that the root device name of the officail CentOS AMI is /dev/sda prevents to recognize /dev/sda3 prepared by AWS. How about to think to switch the root device from /dev/sda to /dev/sda1 on the official CentOS AMI, it is the default value for the root device? in the mean time, I can launch an instance of m1.small with /dev/sda3 visible in the following steps. ===== 1) launch an instance from 'CentOS 6.3 i386 Release Media' AMI (actually ami-2a44fa2b in Tokyo Region) 2) edit the following two files. 2-1) /etc/fstab --- /etc/fstab.orig 2012-10-31 15:55:46.635530167 +0000 +++ /etc/fstab 2012-12-25 16:38:20.533626775 +0000 @@ -1,4 +1,4 @@ -/dev/xvde / ext4 defaults 0 0 +/dev/xvde1 / ext4 defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 tmpfs /dev/shm tmpfs defaults 0 0 proc /proc proc defaults 0 0 2-2) /boot/grub/grub.conf --- /boot/grub/grub.conf.orig 2012-10-31 15:55:46.638530499 +0000 +++ /boot/grub/grub.conf 2012-12-25 16:39:24.477627807 +0000 @@ -3,5 +3,5 @@ title CentOS-6.3-i386-GA-s3 2.6.32-279.el6.i686 root (hd0) - kernel /boot/vmlinuz-2.6.32-279.el6.i686 root=/dev/xvde ro + kernel /boot/vmlinuz-2.6.32-279.el6.i686 root=/dev/xvde1 ro initrd /boot/initramfs-2.6.32-279.el6.i686.img 3) take a snapshot of the root EBS volume 4) register an AMI image with the snapshot with the following command ec2-register --region XX-XXXXXXXX-X -n 'ZZZZ' -d 'ZZZZ --root-device-name /dev/sda1 -b /dev/sda1=snap-237fe703 -a i386 --kernel aki-42992843 * the kernel ID is for i 386 on ap-northeast-1 (Tokyo) region. === furthermore, i suggest to prepare the fstab with the following line for i386 image: /dev/xvde3 swap swap defaults 0 0 it would be nice for people using the AMI on m1.small and c1.medium. Best regards, Mak

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Re: [CentOS-virt] CentOS-virt Digest, Vol 64, Issue 6
by 李成双 21 Dec '12

21 Dec '12

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(no subject)
by Shawn Everett 09 Dec '12

09 Dec '12

Hi All, I have recently installed CentOS 6.3 with QEMU+KVM for Virtualization. I have successfully created a Windows 2003 VM with 4GB of RAM. The host server is an HP ML350 G8 with 24GB RAM and 24 cores. Details of one of the cores is shown below: processor : 23 vendor_id : GenuineIntel cpu family : 6 model : 45 model name : Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz stepping : 7 cpu MHz : 1200.000 cache size : 15360 KB physical id : 1 siblings : 12 core id : 5 cpu cores : 6 apicid : 43 initial apicid : 43 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 x2apic popcnt aes xsave avx lahf_lm ida arat epb xsaveopt pln pts dts tpr_shadow vnmi flexpriority ept vpid bogomips : 3989.86 clflush size : 64 cache_alignment : 64 address sizes : 46 bits physical, 48 bits virtual power management: On an otherwise completely idle system I've noticed the load to be 1.0 to 1.5 range. Running "top" shows the culprit to be: qemu-kvm. Is this normal behavior? I would have expected the load to be pretty light. Stopping the VM restores the load to normal once again. Is there anything I can do to reduce the load? Shawn

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OpenNebula on CentOS-6
by Karanbir Singh 06 Dec '12

06 Dec '12

hi, Some of you might have seen the email on the centos-devel list, for the rest I just wanted to point out that we've been working on getting opennebula ( http://www.opennebula.org/ ) rpms and contextualised images for opennebula available with a very low barrier to entry for CentOS. The 'win' with OpenNebula is that its easy to install, easy to get going, scales well and mostly stays our of your way to let you pick the technologies you want to run your cloud instance. And the CentOS buildsystem runs on it ( has done for a while now.. ) http://lists.opennebula.org/pipermail/users-opennebula.org/2012-December/02… is a link to the announcement upstream, but feel free to either followup here, on the centos-devel list or on the opennebula-users list. - KB -- Karanbir Singh +44-207-0999389 | http://www.karan.org/ | twitter.com/kbsingh ICQ: 2522219 | Yahoo IM: z00dax | Gtalk: z00dax GnuPG Key : http://www.karan.org/publickey.asc

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