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Centos-6, LVM and KVM guest image
by James B. Byrne 30 Aug '11

30 Aug '11

CentOS-6.0 I created an lv (120 Gb) to hold the image of a KVM guest instance. I mounted this at /var/lib/libvirt/images/lv_guest01. When I do a df I see the lv is mounted at the desired location. When I run the virtual machine manager from the desktop I am given the option to install the image into the root directory tree or to browse for an alternative location. When I browse to the mount point of the lv then the virtual machine manger becomes non-responsive and I get a swirling circular pattern in the right hand pane of the file browser. In CentOS-5.6 I was able to create and mount new lvs and then install kvm guests into them through the virtual machine manager. On CentOS-6, even though I added an lv containing 120Gb I am only given the option to create a new volume in the original root location, which itself is a lv, albeit of just 64 Gb. I do not see the additional storage. What step am I missing here? -- *** 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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compress raw image
by Rainer Traut 22 Aug '11

22 Aug '11

Hi, I need to transfer a local raw image to another datacenter. Is there a way to achieve good compression of this image, I heard of tools overwriting unused space with zeros. Is this a good idea? It's an W2k8 image/NTFS. Thx Rainer

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small cloud interface : http://karesansui-project.info/
by Karanbir Singh 20 Aug '11

20 Aug '11

hi guys, just wondering if anyone had feedback about this project : http://karesansui-project.info/ ; I had a go at setting it up, and it took about 5 minutes to get going and be productive. their installer is extremely odd, its a tarball with RPMS ( although they do provide a yum repo as well ). And its based on CentOS ( hardwired version numbers from centos-5.3 to 5.5 - does not seem to like 5.6 unless you change their detection string, not sure why ). - KB

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profiling KVM i/o on CentOS 5
by Nick 18 Aug '11

18 Aug '11

Hi, I am wondering what tools are available to troubleshoot KVM I/O problems on CentOS 5, given that the kernel is 2.6.18 with some backports to support virtualisation? kvm_stat / kvmtrace - These seem to be available in the kvm-tools package. ftrace related things seem not to be available. OProfile is available, can it be used? Also, SystemTap is available, can it be used? Anything else? I don't currently have any experience using any of those, except for a brief experiment with OProfile, but my impression is that it's more of an event-counting tool - I'm not sure it can time function call execution times. Which makes me think SystemTap is better suited. However, this reference [1] makes me wonder if it can only be used with QEMU/KVM CentOS 6. Has anyone any experience or prior art they can share or reference, specifically with profiling virtio_blk? Thanks, Nick 1. > BZ#632722 - This update introduces support for tracing of events within QEMU; > the tracing is similar in its style to DTrace. When used in conjunction with > SystemTap, it is now possible to trace internal QEMU events such as I/O > operations and memory allocations http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/6.1_Techn…

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(no subject)
by Wendy William 18 Aug '11

18 Aug '11

http://www.kiyamato.com/irewin/catalog/images/work.php?html115

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lvm and kvm
by James B. Byrne 15 Aug '11

15 Aug '11

I am performing some configuration testing on a kvm host. When installing a guest operating system is it advisable to place each instance in a separate lv or better to accept the default and store them on the root file system? Respecting lvm, does one configure lvs in a virtual server to take space from the main vg or does one allocate lv space from inside that allocated to the virtual instance? Is it even considered advisable to use lvs with virtual guests? To give an example, if I were to configure an smtp server on bare metal I might use the following disk layout: vg_bare 500Gb / lv_root 8Gb /boot lv_boot 1Gb /tmp lv_tmp 8Gb /var/log lv_log 8Gb /var/spool/mail lv_mail 16Gb In a kvm setup, if I wish to do this, would I first create an lv just to host the virtual image and then assign lv s from the space allocated to that image file? vg_bare 500Gb / lv_root 8Gb /boot lv_boot 1Gb /tmp lv_tmp 8Gb /var/log lv_log 8G /var/lib/libvirt/images/lv_virt01 32Gb /var/lib/libvirt/images/lv_virt02 32Gb . . . and so forth? Or is it worth the bother to have lv s in a virtual host? -- *** 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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Suggestions to improve this minimal kickstart config for CentOS 6?
by Kartik Subbarao 01 Aug '11

01 Aug '11

I've come up with the following kickstart config (see below) for deploying a minimal CentOS 6 VM. It takes about 460MB. I'm assuming that all of the -firmware RPMs aren't needed for a VM installation, so I removed them. Also removed as many selinux packages as possible since I don't need that. I was wondering whether anyone could offer any further suggestions on minimizing the disk usage of the VM image. Also, I wanted to ask whether it might make sense to post this type of configuration to the CentOS wiki, possibly linked from the following page: http://wiki.centos.org/TipsAndTricks/KickStart This might make it easy for people who are building VMs for reference. Thanks, -Kartik ======== lang en_US.UTF-8 keyboard us timezone America/New_York auth --useshadow --passalgo=md5 selinux --disabled firewall --disabled zerombr bootloader --location=mbr network --bootproto=dhcp --device=eth0 --onboot=on services --enabled=network rootpw admin123 clearpart --all --initlabel part / --asprimary --fstype="ext3" --grow --maxsize=1000 --size=1 # Repositories url --url="http://mirrors.kernel.org/centos/6.0/os/x86_64/" %packages --excludedocs --nobase --instLangs=en @Core %post rpm -e $(rpm -qa |grep -i firmware) yum -y remove audit authconfig checkpolicy libsemanage libselinux-utils policycoreutils selinux-policy selinux-policy-targeted rm -rf /etc/selinux/targeted rpm -e --nodeps redhat-logos %end

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idle C6 guest on C6 host constantly using 10% cpu
by Dennis Jacobfeuerborn 29 Jul '11

29 Jul '11

Hi, I'm playing around with KVM virtualization on Centos 6 and I noticed then after I created a regular minimal install in a VM this guest will constantly use 10% of the cpu when idle. Any ideas what the problem might be? Regards, Dennis

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Snapshot error "command savevm not found"
by Trey Dockendorf 29 Jul '11

29 Jul '11

Attempting to take snapshots of VM using virsh with the following command, # virsh -c qemu:///system snapshot-create CentOS6-x86-001 Results in the following error, error: internal error unable to execute QEMU command 'savevm': The command savevm has not been found The VM's virtual disks are qcow2. Below is the XML file for this vm ------------ <domain type='kvm' id='6'> <name>CentOS6-x86-001</name> <uuid>050fb9d8-0b9a-48b9-a432-16eec57a9e8f</uuid> <memory>1024000</memory> <currentMemory>1024000</currentMemory> <vcpu>1</vcpu> <os> <type arch='x86_64' machine='rhel6.0.0'>hvm</type> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/libexec/qemu-kvm</emulator> <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/vmstore/CentOS6-x86-001/CentOS6-x86-001_sys.qcow2'/> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> </disk> <disk type='file' device='cdrom'> <driver name='qemu' type='raw'/> <target dev='hdc' bus='ide'/> <readonly/> <alias name='ide0-1-0'/> <address type='drive' controller='0' bus='1' unit='0'/> </disk> <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/vmstore/CentOS6-x86-001/CentOS6-x86-001_var.img'/> <target dev='vdb' bus='virtio'/> <alias name='virtio-disk1'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/> </disk> <controller type='ide' index='0'> <alias name='ide0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> </controller> <interface type='bridge'> <mac address='52:54:00:4d:74:c7'/> <source bridge='br0'/> <target dev='vnet0'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> <serial type='pty'> <source path='/dev/pts/1'/> <target port='0'/> <alias name='serial0'/> </serial> <console type='pty' tty='/dev/pts/1'> <source path='/dev/pts/1'/> <target port='0'/> <alias name='serial0'/> </console> <input type='tablet' bus='usb'> <alias name='input0'/> </input> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='5900' autoport='yes'/> <video> <model type='cirrus' vram='9216' heads='1'/> <alias name='video0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </video> <memballoon model='virtio'> <alias name='balloon0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> </memballoon> </devices> <seclabel type='dynamic' model='selinux'> <label>system_u:system_r:svirt_t:s0:c292,c580</label> <imagelabel>system_u:object_r:svirt_image_t:s0:c292,c580</imagelabel> </seclabel> </domain> ------------ This is my first attempt at snapshots with KVM after migrating from ESXi, so if there's a better method please let me know. Thanks - Trey

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Send magic-sysrq from virtual serial console?
by David Knierim 28 Jul '11

28 Jul '11

I am using CentOS 5.6 as a KVM host. My guests are running CentOS 5.6 with the only console being a virtual serial console. The guests are configured so magic-sysreq can be used to debug kernel issues. However, in order to send magic-sysrq from a serial port, I need to send a break. How does one send a break on the virtual console serial port provided by KVM/libvirt to guests? Thanks, David

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