Questions tagged [kvm-virtualization]

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-intel.ko or kvm-amd.ko. KVM also requires a modified QEMU although work is underway to get the required changes upstream.

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148
votes
2answers
132k 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 ...
103
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12answers
222k 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 (...
53
votes
2answers
87k 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 ...
41
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7answers
32k 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 ...
40
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5answers
70k 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 ...
37
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7answers
63k views

Xen vs. KVM in performance

What is faster on the 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 ...
35
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5answers
67k 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 ...
32
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3answers
80k views

KVM/libvirt: How to configure static guest IP addresses on the virtualisation host

What I'd like to do is to set the guests' network configuration (IP address, subnet, gateway, broadcast address) from the host system. The used network setup is in bridge mode. How can I configure the ...
30
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7answers
99k 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 ...
29
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6answers
63k views

Incredibly low 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 ...
28
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6answers
82k 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 ...
27
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3answers
24k views

Windows 7 Setup hangs at “Starting Windows” using Proxmox 4.2

I am trying to install Windows 7 on Proxmox Virtual Environment version 4.2-4/2660193c, running on Debian Jessie. I have followed the instructions on this site. I uploaded a known-good Win7 ISO (that ...
25
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5answers
26k 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.
25
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2answers
88k views

Which is better image format, raw or qcow2, to use as a baseimage for other VMs?

I am using a baseimage and based on that creating many VMs. And now I want to know which is better, qcow2 or raw to use for a baseimage. Moreover, can you please tell me if there is any advantage of ...
24
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4answers
36k 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 ...
24
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1answer
37k 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 ...
23
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9answers
35k 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 ...
22
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1answer
58k views

how to delete a guest after creating it with virt-install

I created a KVM guest from the command line with virt-install where I used the command line options --disk pool=vg0,size=20 and --name virt1.example.com. How can I delete this KVM guest from the ...
22
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5answers
80k 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 ...
22
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4answers
30k 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 ...
21
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-...
21
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5answers
85k 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+...
20
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2answers
9k views

Converting Windows 2012 R2 from Hyper-V to KVM (qemu)

I have a Windows Server 2012 R2 running SharePoint 2013 which I am trying to migrate from Hyper-V to KVM (qemu). I have converted the vhdx file to qcow2 format and copied it across to the KVM server (...
18
votes
5answers
16k 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 ...
17
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2answers
5k 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 ...
17
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2answers
13k views

Is KVM a type 1 or type 2 hypervisor? [closed]

Is KVM a type 1 or a type 2 hypervisor? I understand that type 1 hypervisors run on bare metal while type 2 hypervisors are applications running on top of an operating system (such as VMware ...
16
votes
4answers
23k 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)...
15
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5answers
22k views

Is online disk resize possible with KVM?

We're evaluting KVM for Linux virtualization on a few projects. All is going well so far. But one of our requirements is the ability to add disk space to a running guest without rebooting or taking it ...
15
votes
3answers
23k 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 ...
15
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15answers
42k 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
2answers
42k 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? ...
15
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7answers
4k 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
7k 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
7k 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
4answers
13k 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 ...
14
votes
1answer
5k views

KVM guest cannot write to 9p share owned by non-root

I am aiming to set up full write access to a 9p share for a KVM guest. Both host and guest have the same users/groups with the same IDs. Both host and guest should be able to write to the share using ...
13
votes
8answers
3k 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 ...
13
votes
4answers
48k views

Change amount of Ram and CPU cores in KVM

How can I Change amount of Ram and CPU cores for a virtual machine in KVM that is already created? Thanks
13
votes
1answer
41k 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 ...
13
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. ...
13
votes
5answers
5k 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 ...
13
votes
4answers
37k views

How do I enable KVM device passthrough in Linux?

I have an MSI-GD65 Gaming motherboard and an Intel i7 4790. VT-D is enabled in the CPU Features section of the bios. I'm running Ubuntu 14.04.1 LTS and when I try and detach a device, I get the ...
13
votes
4answers
15k 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 ...
12
votes
5answers
24k 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 ...
12
votes
3answers
24k views

How to change the default Storage Pool from libvirt?

I'm trying to use a different Storage Pool on KVM in order to store the virtual disks of my VMs and also the ISOs from the operating systems which I'm using. For example: I want to use the directory /...
12
votes
5answers
9k views

Solidworks: activation license mode is not supported in this virtual environment (Qemu-KVM)

The question is not around Solidworks actually, so please continue to read. The whole idea of virtualization is to be hardware independent. Before our eyes a whole new dependency level is being ...
12
votes
3answers
25k views

Is there any way to shrink qcow2 image without converting it raw?

Is there any way to shrink qcow2 image without converting it raw? I cannot convert it to raw because I don't have disk space enough for raw image.
12
votes
1answer
1k views

KVM Host with 88 physical cores uses only 14 on 64 core Guest

I do have a server with 2 CPUs (22 Cores each plus HT). I created a KVM Guest with 64 allocated cores. When I run a compilation task the virtual machine shows all 64 cores at 100% (at moderate Disk I/...
12
votes
5answers
27k 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 ...
12
votes
3answers
8k 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 ...

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