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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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 ...
Abhishek Gupta's user avatar
127 votes
18 answers
304k 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 (...
slm's user avatar
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59 votes
5 answers
122k 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 ...
Onitlikesonic's user avatar
56 votes
2 answers
98k 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 ...
user avatar
47 votes
3 answers
140k 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 ...
beta's user avatar
  • 705
46 votes
6 answers
103k 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 ...
steveh7's user avatar
  • 463
43 votes
5 answers
91k 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.
YOU's user avatar
  • 591
41 votes
7 answers
34k 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 ...
minWi's user avatar
  • 511
40 votes
7 answers
73k 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 ...
SyRenity's user avatar
  • 3,189
40 votes
9 answers
145k 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 ...
slm's user avatar
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39 votes
6 answers
93k 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 ...
El Yobo's user avatar
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37 votes
6 answers
60k 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 ...
bmaeser's user avatar
  • 689
35 votes
6 answers
108k 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 ...
badbishop's user avatar
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35 votes
2 answers
124k 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 ...
A-B's user avatar
  • 603
33 votes
2 answers
34k 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 ...
Pétur Ingi Egilsson's user avatar
29 votes
5 answers
124k 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 ...
ΤΖΩΤΖΙΟΥ's user avatar
28 votes
5 answers
31k 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.
Arthur Ulfeldt's user avatar
27 votes
3 answers
26k 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 ...
Alexander Foken's user avatar
27 votes
1 answer
43k 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 ...
Daniele Testa's user avatar
27 votes
1 answer
68k 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 ...
Erik Sjölund's user avatar
26 votes
9 answers
46k 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 ...
fadedbee's user avatar
  • 2,088
24 votes
6 answers
73k views

How to automatically start VM created by virt-manager?

I have created a virtual machine with virt-manager that runs on kvm/qemu. The machine works well when started through virt-manager. However, I would like to be able to start and stop the VM through ...
user avatar
24 votes
4 answers
42k 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 ...
Jared's user avatar
  • 383
23 votes
4 answers
59k 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 /...
ivanleoncz's user avatar
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22 votes
4 answers
60k views

Exporting libvirt+KVM virtual machines to files

I am going to retire an old libvirt + KVM server, but I need to preserve the VMs. Unfortunately, the network is down and I cannot create connections to the system. Is there any way to export the VMs ...
bayindirh's user avatar
  • 694
22 votes
5 answers
98k 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+...
PythonLearner's user avatar
22 votes
6 answers
25k 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 ...
Hristo Hristov's user avatar
21 votes
4 answers
85k 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
Zim3r's user avatar
  • 1,504
21 votes
2 answers
4k 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-...
Volodymyr Melnyk's user avatar
21 votes
3 answers
18k 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 (...
dross's user avatar
  • 395
20 votes
2 answers
7k 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 ...
Martin's user avatar
  • 372
19 votes
9 answers
53k views

Is there a way to determine which virtual interface belongs to a virtual machine in a kvm host?

I'm using qemu/kvm whith bridged networking. In the host machine there are several "vnetX" network interfaces without IP. I'm looking for a way to know which vnetX belong to a virtual machine. I ...
theist's user avatar
  • 1,249
19 votes
4 answers
72k 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 ...
Anonymouslemming's user avatar
19 votes
4 answers
33k 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)...
Andrew Clegg's user avatar
18 votes
1 answer
21k views

What is fastest way to copy a sparse file? What method results in the smallest file?

BACKGROUND: I'm copying a sparse qcow2 VM image that is 200GB in size, but has 16GB of allocated blocks. I've tried various methods to copy this sparse file within the same server and have some ...
Steve Amerige's user avatar
17 votes
1 answer
38k views

QEMU multiple port forwarding

I would like to forward more than one port. This command run my VM and forwards RDP port successfully: qemu-system-i386 -net nic,model=rtl8139 -net user,hostfwd=tcp::3389-:3389 -m 512M -localtime -...
Anna Parker's user avatar
17 votes
3 answers
8k 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 ...
Greendrake's user avatar
  • 1,421
16 votes
5 answers
32k 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 ...
Eil's user avatar
  • 389
16 votes
1 answer
14k views

Delete "orphan" libvirt snapshot

I am trying to live-snapshot using KVM as per this procedure. I must have messed up at some point because I'm in a state I don't understand. My VM is called prod. It was created in file /srv/vm/prod....
Jérôme's user avatar
  • 645
16 votes
3 answers
29k 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 ...
Soviero's user avatar
  • 4,376
16 votes
4 answers
12k views

virsh console and tty size

I have a virtualization server to which I connect over ssh. If I now change the size of the window it will automatically propagate to the server. It's most easily seen using stty -a, checking the ...
pehrs's user avatar
  • 8,879
16 votes
7 answers
5k 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 ...
senorsmile's user avatar
15 votes
5 answers
32k 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 ...
jkp's user avatar
  • 429
15 votes
5 answers
21k views

how to find out if running inside KVM guest

Is there a way to find out if OS(linux) is running inside KVM guest..
suyogdotstar's user avatar
15 votes
3 answers
33k views

libvirt: how can I make a domain start when the host starts?

I would like some of my domains to start automatically when my host starts (I'm using libvirt+KVM on ubuntu). I guess I could put some "virsh start..." statements in rc.local, but is there a way to ...
kdt's user avatar
  • 1,410
15 votes
15 answers
46k 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 ...
Tim's user avatar
  • 215
15 votes
2 answers
48k 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? ...
telemaco's user avatar
  • 251
14 votes
5 answers
92k views

virsh: VM console does not show any output

I have a VM which I can start with virsh. According to virsh dumpxml VM1, this is the allocated pty: <serial type='pty'> <source path='/dev/pts/6'/> <target port='0'/> <...
blueFast's user avatar
  • 4,320
14 votes
4 answers
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 ...
Devator's user avatar
  • 1,483
14 votes
8 answers
32k 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 ...
rascher's user avatar
  • 1,148

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