KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-...

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54
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2answers
42k views

Difference between KVM and QEMU

I have been reading about KVM and Qemu for sometime. As of now I have a clear understanding of what they do. KVM supports hardware virtualization to provide near native performance to the Guest ...
48
votes
8answers
94k views

How do you increase a KVM guest's disk space?

I setup an Ubuntu guest on a CentOS KVM host with initially 6GB of disk space. How do I go about increasing the Ubuntu guest's disk space from the command line? EDIT #1: I'm using a disk image file (...
44
votes
2answers
60k views

Difference between Xen PV, Xen KVM and HVM?

I know that Xen is usually better than OpenVZ as the provider cannot oversell in Xen. However, what is the difference between Xen PV, Xen KVM and HVM (I was going through this provider's specs? Which ...
39
votes
7answers
26k views

Replace VMware vSphere infrastructure with open source alternatives?

We are planning a slow migration from VMware (and third party apps) to open source alternatives (free would be great). Basically, we want to start with some little cluster lab, then migrate the ...
34
votes
7answers
60k views

Xen vs KVM in performance

What is faster on same hardware - Xen or KVM? I'm trying to pick-up a virtualization technology to work, which gives the best performance. There are some benchmarks here that I found on the subject: ...
24
votes
4answers
32k views

Forwarding ports to guests in libvirt / KVM

How can I forward ports on a server running libvirt/KVM to specified ports on VM's, when using NAT? For example, the host has a public IP of 1.2.3.4. I want to forward port 80 to 10.0.0.1 and port 22 ...
20
votes
2answers
3k views

Very strange file size (more than 600 PB) on a small filesystem

I had a file on an XFS filesystem which size was about 200 GB. It was a QCOW2 image containing a virtual disk of a KVM-driven virtual machine. Something went wrong (maybe it was some glitch of qemu-...
20
votes
4answers
44k views

How to connect a cdrom device to a kvm/qemu domain (using command-line tools)?

I have set up a virtual machine running Windows XP on my Ubuntu laptop. Using the virt-manager GUI application, I can insert a CD in my drive and go to Details→IDE CDROM 1 and click on the Connect ...
20
votes
6answers
46k views

KVM Guest installed from console. But how to get to the guest's console?

I'm trying to install a fully virtualized guest (Fedora 14 x86_64) on KVM (RHEL 6), using command-line only (both hypervisor and guest). It goes without errors, and without a tangible result . I'd ...
19
votes
1answer
24k views

KVM and Libvirt - How do I hotplug a new virtio disk?

I am trying to hot-add a file-based disk to a running KVM virtual server. I've created a new disk from scratch using the command dd of=/home/cloud/vps_59/test.img bs=1 seek=5G count=0 and I was ...
19
votes
5answers
43k views

Is there a way to run virt-manager on Windows?

We've been using KVM for almost a year strictly on CentOS 5.x as the KVM host, with Fedora and Ubuntu workstations accessing the KVM host and its guests using virt-manager, virt-viewer, and ssh. Is ...
18
votes
4answers
14k views

how to rename a VM using libvirt+KVM

How can I rename a VM on KVM+libvirt? I would like it to change the name in the 'inventory' as well as change the name of the storage etc.
17
votes
5answers
45k views

KVM: Which CPU features make VMs run better?

We are using Ubuntu 12.04 with the following parameters: Dell R910 Kernel 3.2.0-25-generic #40-Ubuntu SMP x86_64 x86_64 x86_64 GNU/Linux kvm 1:84+dfsg-0ubuntu16+1.0+noroms+0ubuntu13 qemu-kvm 1.0+...
16
votes
4answers
14k views

KVM/qemu - use LVM volumes directly without image file?

I'm not quite sure how to phrase this question (hence the poor title), so let me provide an example of what I'm trying to do. On my (old) Xen host, I'm able to present LVM filesystems directly to ...
15
votes
5answers
27k views

Incredibly slow KVM disk performance (qcow2 disk files + virtio)

I'm having some serious disk performance problems while setting up a KVM guest. Using a simple dd test, the partition on the host that the qcow2 images reside on (a mirrored RAID array) writes at ...
15
votes
2answers
3k views

understanding relationship between Qemu and KVM

What is the difference between KVM and Qemu? As I understand, latter is able to provide "user mode emulation" which means that one can run a single executable built for some other architecture like ...
15
votes
15answers
38k views

Web based KVM management for Ubuntu

We've got a single Ubuntu 9.10 root server on which we want to run multiple KVM virtual machines. To administer these virtual machines I'd like a web based KVM management tool, but I don't know which ...
15
votes
7answers
3k views

recommendations for efficient offsite remote backup solution of vm's

I am looking for recommendations for backing up my current 6 vm's(and soon to grow to up to 20). Currently I am running a two node proxmox cluster(which is a debian base using kvm for virtualization ...
14
votes
4answers
6k views

Improving IO with FlashCache

I have a server with 2 HDD's (2x 1 TB), running in RAID 1 (SW-RAID). I want to improve IO performance by using flashcache. There are running KVM virtual machines on it, using LVM. Regarding this, I ...
14
votes
7answers
6k views

Tough Choice: Xen or KVM

I'm building a fresh workstation and want to use Linux alongside Windows. This seems like a good opportunity to get acquainted with with either Xen or KVM. So I face a choice. In favour of using ...
14
votes
3answers
17k views

free up not used space on a qcow2-image-file on kvm/qemu

we are using kvm/qemu with qcow2-images for our virtual machines. qcow2 has this nice feature where the image file only allocates the actually needed space by the virtual-machine. but how do i shrink ...
14
votes
3answers
14k views

Correct way to move kvm vm

I'm wondering what is the correct way of moving a VM between two KVM hosts without using any kind of shared storage Would copying the disk files and the XML dump from the source KVM machine to the ...
13
votes
5answers
4k views

Considerations when chosing AMD processors over Intel

I work for a company with a lot of legacy LAMP web-applications, where we are trying to refresh our hardware from ~250 physical servers to ~40 new servers w/virtualization. We have received two ...
12
votes
8answers
2k views

Free hypervisor for small configuration

I'm building a server for virtualization for a non profit organization. I was planning on employing VMware ESXI free but I'm second guessing my plan because newer ESXI don't seem to be well supported ...
12
votes
3answers
14k views

Snapshot/rollback for libvirt+KVM?

I've recently begun using KVM for my development/test environment on a Linux host system with 8G memory. Prior, I was using VMware Fusion for my virtual environment, but my Macbook only has 2G memory. ...
12
votes
5answers
7k views

Port Forwarding from Host to Guest with libvirt 0.8.3 Using KVM on Ubuntu

The host has a single external IP available, so I set my KVM guests up with NAT. How do I set up a port forwarding to forward some of the requests from the outside to the guests? I couldn't find ...
12
votes
5answers
5k views

what cluster management software to use for linux?

I have found the following cluster management software tools: pacemaker (clusterlabs.org), - original a Heartbeat project, focus for high-availability, will be in the next debian version openqrm (...
11
votes
8answers
19k views

How do you synchronise huge sparse files (VM disk images) between machines?

Is there a command, such as rsync, which can synchronise huge, sparse, files from one linux server to another? It is very important that the destination file remains sparse. It may be longer (but ...
11
votes
4answers
10k views

Backing up qcow2 kvm guests

I can't find any good info on backing up qcow2 kvm guests. I'm not really interested in the guests running state, only the file system. This question suggests using savevm but that creates a snapshot ...
11
votes
3answers
6k views

LVM volume group shared between KVM/libvirt host and guests: is this a bad idea?

I have just built a shiny new KVM/libvirt-based virtual machine host, containing 4 SATA II hard drives, and running CentOS 5.5 x86_64. I have decided to create virtual machine disks as logical ...
10
votes
3answers
14k views

Hyper Threading and Virtual Machines?

I already looked at this thread: Hyper-V and Hyper-threading: On or off?, but the only answer is Windows specific.... I am building a VM server (using Proxmox VE if that makes a difference) and was ...
10
votes
4answers
6k views

How to keep time on resumed KVM guest with libvirt?

On my host I am using libvirt and a KVM guest. When the host is shutting down, libvirt suspends the guest. When the host is starting up, libvirt resumes the guest. The problem is, if the guest is ...
10
votes
9answers
5k views

Is anyone using KVM in production?

I've been trying to set up a pair of servers utilising KVM on Ubuntu 9.10 to host 8 virtual machines between them and ended up with various issues from the VMs freezing, to not powering on. I had one ...
10
votes
4answers
13k views

Can KVM suspend or shutdown guests automatically on host shutdown?

We have a CentOS 5.5 KVM host, running guests with various versions of CentOS and possibly other OSes later. We'd like to be able to either (a) automatically send an ACPI shutdown to all guests or (b)...
9
votes
5answers
13k views

Why does my Windows 7 VM running under Linux' KVM not use all the virtual processors?

All I've had a problem on my server since I migrated one of my VM's from Windows 2008 Server to Windows 7 (ultimate): though I've assigned four cores to the VM and it even seems to see them, it seems ...
9
votes
4answers
23k views

How to mount virtual machine's LVM partition on KVM host?

If I trying to do following on KVM host: # kpartx -av /dev/VolGroup00/kvm101_img add map kvm101_img1 : 0 208782 linear /dev/VolGroup00/kvm101_img 63 add map kvm101_img2 : 0 125612235 linear /dev/...
9
votes
8answers
2k views

Virtualization: Guest in guest?

Does it make any sense to run a virtual machine with a "master" guest, and in that master guest run many other guests? Has anyone tested this? Is it even possible? Are there better ways to accomplish ...
9
votes
2answers
6k views

KVM on Illumos (OpenIndiana vs. SmartOS)

I'm considering virtualizing a number of guests onto a single server running a recent port of KVM to Illumos. It sounds like my two primary options will be OpenIndiana and SmartOS. The distribution ...
9
votes
3answers
5k views

use LXC under heavier virtualization (Xen, KVM,Hyper-V,VMVare)

Is it possible to use LXC under heavier virtualization (Xen DomU, KVM, Hyper-V, VMVare) ? I would like to use it as security (isolation) tool, the ability to limit resource consumption is not priority ...
9
votes
2answers
8k views

Access KVM virtual machines over VNC without port forwarding with SSH

Is it possible to access the VMs without having to forward the remote port and VNC to the localhost? I'd like to be able to VNC into the KVM server and see the VMs display.
9
votes
5answers
18k views

Why is idle windows VM using so much CPU?

I have 2 VMs running as guests on a KVM virtualization platform running on Ubuntu 10.04. One VM is an Ubuntu 10.04 system, the other is a Windows 7 system. When both machines are completely logged ...
9
votes
2answers
17k views

Strongswan vpn tunnel connected but the traffic is not routed through it

I have just set up a vpn tunnel site-to-site with strongswan (4.5). The tunnel looks fine and connected to the other side, but seems there is a problem routing traffic through the tunnel. Any idea? ...
9
votes
2answers
5k views

Jumbo frames between KVM guest and host?

I am trying to implement a 9000 byte MTU for storage communication between KVM guests and the host system. The host has a bridge (br1) with a 9000 byte MTU: host# ip link show br1 8: br1: <...
9
votes
5answers
3k views

libvirt: Change dhcp-setup without restarting

I'm using libvirt and kvm to virtualize my server. I configured libvirt to start a dhcp-server on the bridge-network-interface to give the vm's their ips. Every VM's gets always the same ip based on ...
8
votes
1answer
22k views

KVM guest io is much slower than host io: is that normal?

I have a Qemu-KVM host system setup on CentOS 6.3. Four 1TB SATA HDDs working in Software RAID10. Guest CentOS 6.3 is installed on separate LVM. People say that they see guest performance almost equal ...
8
votes
2answers
3k views

How to quit QEMU monitor?

I launched KVM VM with this command: kvm /kvm/hdd/v1/v1-1.raw -m 512 -daemonize -smp 2 -nographic -net nic,model=virtio,macaddr=aa:aa:aa:aa:aa:01 -net tap,ifname=tap0 -monitor telnet:localhost:7001,...
8
votes
3answers
14k views

What KVM disk type to use?

I'm setting up a few KVM virtual guests and I'm debating which disk type to use. I haven't been able to find a good resource online that runs down the pros and cons of each. Can you help me create a ...
8
votes
7answers
10k views

Get list of DHCP clients with KVM+libvirt?

I have several VMs running on Ubuntu 9.10 via KVM+libvirt. I want to be able to find out the IP address that has been assigned to each host without physically opening a physical "console" to each ...
8
votes
2answers
277 views

Can i pause VM's while power-cycling iscsi storage array

Unfortunately I may have to power-cycle my storage array. In the context of using KVM with libvirt managing the Virtual Machines where i need to power-cycle the storage array, is it possible or even ...
8
votes
2answers
16k views

Changing boot device for a QEMU-KVM virtual machine

I am trying to change the boot device for a VM. I go to the VM's XML file in /etc/libvirt/qemu and set <boot dev='cdrom' />. Still, it attempts to boot from the harddrive instead of the cdrom. ...