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#title The Kernel Virtual Machine
 
#title The Kernel Virtual Machine
 
== Introduction ==
 
== Introduction ==
=== Preliminary notes ===
+
Ubuntu uses [http://www.linux-kvm.org/page/Main_Page KVM] as the backend virtualisation technology and [http://libvirt.org/ libvirt] as its toolkit/API.  Libvirt frontends for managing VMs include [http://virt-manager.et.redhat.com/ virt-manager] (GUI) or virsh (CLI). Alternative management options include [http://www.convirture.com/ convirt] (GUI) or [http://www.convirture.com/wiki/index.php?title=Convirt2_Installation convirt2] (WWW).
* '''This is still work in progress! Feel free to jump in and extend this documentation! '''
+
== Documentation ==
* '''The previous version of this page (which was documenting KVM for Feisty) has been moved to [[KVMFeisty]]'''
+
* [[UbuntuHelp:KVM/Installation|Installation]] - Installation and removal of KVM
 +
* [[UbuntuHelp:KVM/Networking|Networking]] - Network configuration; includes bridging
 +
* [[UbuntuHelp:KVM/CreateGuests|Guest Creation]] - Creation of different kinds of guests
 +
* [[UbuntuHelp:KVM/Managing|Guest Management]] - Management of guests; command line or graphically
 +
* [[UbuntuHelp:KVM/Directly|KVM Directly]] - Using KVM directly (without libvirt)
 +
* [[UbuntuHelp:KVM/FAQ|FAQ]] - Frequently asked questions, troubleshooting tips and other recommendations
 +
== Notes ==
 +
* '''The previous version of this page (which was documenting KVM for Feisty) has been moved to [[UbuntuHelp:KVMFeisty|KVMFeisty]]'''
 
* '''Also checkout the official docs, http://doc.ubuntu.com/ubuntu/serverguide/C/virtualization.html'''
 
* '''Also checkout the official docs, http://doc.ubuntu.com/ubuntu/serverguide/C/virtualization.html'''
* The use case targeted when KVM was moved into main is '''"Single host server virtualization"'''.  This means that even though KVM can be used to serve other purposes, it has been designed to be run on Ubuntu Server Edition to host server operating systems.  If you are looking for a desktop virtualization tool, [[UbuntuHelp:VirtualBox|VirtualBox]], Parallel workstation or [[UbuntuHelp:VMware|VMware]] Player/Server can be more suitable alternatives.
+
* The use case targeted when KVM was moved into main is '''"server virtualization"'''.  This means that even though KVM can be used to serve other purposes, it has been designed to be run on Ubuntu Server Edition to host non-graphical server operating systems.  If you are looking for software to serve graphically-based virtual machines, [[UbuntuHelp:VirtualBox|VirtualBox]], Parallels Workstation (or Parallels Desktop for Mac), or [[UbuntuHelp:VMware|VMware]] Player/Server are more suitable alternatives.
=== Basic info ===
+
Ubuntu uses [[http://kvm.qumranet.com/|kvm]] as the backend virtualisation technology. To manage VMs we use [[http://libvirt.org/|libvirt]] as the basic toolbox and [[http://virt-manager.et.redhat.com/|virt-manager]] as the graphical frontend for managing your vm's.
+
== How to get started ==
+
=== How to check if your CPU supports hardware virtualisation ===
+
To run KVM, you need a processor that supports virtualisation; Intel and AMD both have developed extensions for their processors, respectively INTEL-VT and AMD-V. To see if your processor supports one of these, you can run the following command:
+
<pre><nowiki>
+
egrep '(vmx|svm)' /proc/cpuinfo
+
 
+
</nowiki></pre>
+
If nothing is printed, it means that your CPU doesn't support hardware virtualisation. Otherwise, it does - but you still need to make sure that virtualisation is enabled in the BIOS.
+
=== Use a 64 bit kernel if you need more than 2GB RAM for your VMs ===
+
To serve more than 2047 MB of RAM for your VMs, you '''must''' use a 64 bit kernel (see [[32bit_and_64bit]]). On a 32 bit kernel install, you'll be limited to 2GB RAM at maximum for a given VM.
+
To see if your processor is 64 bit, you can run the following command:
+
<pre><nowiki>
+
grep ' lm ' /proc/cpuinfo
+
</nowiki></pre>
+
If nothing is printed, it means that your CPU is not 64 bit. ''lm'' stands for Long Mode, so 64 bit CPU.
+
To see if your running kernel is 64 bit, just issue the following command:
+
<pre><nowiki>
+
uname -m
+
</nowiki></pre>
+
'''x86_64''' indicates a 64-bit kernel running. If you use see i386, i486, i586 or i686, you're running a 32 bit kernel.
+
=== Installation of KVM ===
+
For the following setup, we will assume that you are deploying KVM on a server, and therefore do not have any X server on the machine.
+
You need to install a few packages first:
+
<pre><nowiki>
+
$ sudo apt-get install kvm libvirt-bin ubuntu-vm-builder qemu bridge-utils
+
</nowiki></pre>
+
* libvirt-bin provides libvirtd which you need to administer qemu and kvm instances using libvirt
+
* kvm is the backend
+
* ubuntu-vm-builder powerful command line tool for building virtual machines
+
* bridge-utils provides a bridge from your network to the virtual machines
+
You might also want to install ''virt-viewer'', for viewing instances
+
'''8.10 (intrepid) Notes''':
+
* Two meta packages have been added: <code><nowiki>ubuntu-virt-server</nowiki></code> and <code><nowiki>ubuntu-virt-mgmt</nowiki></code>.  <code><nowiki>Ubuntu-virt-server</nowiki></code> installs the packages needed to setup a base virtulization host (kvm, libvirt-bin and openssh-server) and <code><nowiki>ubuntu-virt-mgmt</nowiki></code> installs what you need to administer it from a management station (virt-manager, python-vm-builder and virt-viewer). 
+
* <code><nowiki>ubuntu-vm-builder</nowiki></code> has been replaced by <code><nowiki>python-vm-builder</nowiki></code> ([[JeOSVMBuilder|tutorial]]).
+
=== Adding Users ===
+
Add yourself to the ''libvirtd'' group (note that there is no need to add yourself to the ''kvm'' group):
+
<pre><nowiki>
+
$ sudo adduser `id -un` libvirtd
+
</nowiki></pre>
+
This will give you access to the system-wide libvirtd instance. This is preferable for you because it gives you access to the advanced networking options rather than simply the "userspace networking" option as you may know it from QEmu.
+
'''Note: You need to log out and log back in for the new group membership to take effect.'''
+
Note: The `id -un` command will return the current username, for example if your username is ''joe'' you will be effectively be running ''sudo adduser joe libvirtd''.
+
You can test if your install has been successful with the following command:
+
<pre><nowiki>
+
$ virsh -c qemu:///system list
+
Id Name                State
+
----------------------------------
+
 
+
$
+
</nowiki></pre>
+
If on the other hand you get something like this:
+
<pre><nowiki>
+
$ virsh -c qemu:///system list
+
libvir: Remote error : Permission denied
+
error: failed to connect to the hypervisor
+
$
+
</nowiki></pre>
+
Something is wrong and you probably want to fix this before you move on. The critical point here is whether or not you have write access to ''/var/run/libvirt/libvirt-sock''.
+
== Networking ==
+
There are a few different ways to allow a virtual machine access to the external network. The default virtual network configuration is usermode networking, which uses the SLIRP protocol and traffic is NATed through the host interface to the outside network. If you do not want to access network services on your virtual machine then you can skip this next step.
+
However to enable external hosts to directly access services on virtual machines a bridge needs to be configured. This allows the virtual interfaces to connect to the outside network through the physical interface, making them appear as normal hosts to the rest of the network.
+
'''Warning:''' Network bridging will not work when the physcial network device (eg eth1, ath0) used for bridging is a wireless device (eg ipw3945), as most wireless device drivers do not support bridging!
+
'''Warning 2:''' It seems that due to the implementation of CAP_NET_ADMIN in kernel 2.6.18, root access is needed to bring tap interfaces up and down. This means you'll need to run the VM Manager with gksudo (bad) or place a wrapper around the bits that bring up the taps (messy). More info when I figure this one out. (srodden)
+
=== Creating a network bridge on the host ===
+
We are going to change the network configuration. To do it properly, we should first stop networking<<FootNote(This is needed for example when you move from DHCP to static address: it will stop the DHCP client, which a restart won't do if you changed the configuration already. If you are changing this remotely, then you should prepare your new configuration into a separate file and the use a script to stop networking, put the new configuration in place and start it back.)>>:
+
<pre><nowiki>
+
invoke-rc.d networking stop
+
</nowiki></pre>
+
To setup a bridge interface, edit /etc/network/interfaces and either comment or replace the existing config with (replace with the values for your network):
+
<pre><nowiki>
+
auto lo
+
iface lo inet loopback
+
 
+
auto eth0
+
iface eth0 inet manual
+
 
+
auto br0
+
iface br0 inet static
+
        address 192.168.0.10
+
        network 192.168.0.0
+
        netmask 255.255.255.0
+
        broadcast 192.168.0.255
+
        gateway 192.168.0.1
+
        bridge_ports eth0
+
        bridge_fd 9
+
        bridge_hello 2
+
        bridge_maxage 12
+
        bridge_stp off
+
 
+
</nowiki></pre>
+
or to use DHCP
+
<pre><nowiki>
+
auto lo
+
iface lo inet loopback
+
 
+
auto eth0
+
iface eth0 inet manual
+
 
+
auto br0
+
iface br0 inet dhcp
+
        bridge_ports eth0
+
        bridge_fd 9
+
        bridge_hello 2
+
        bridge_maxage 12
+
        bridge_stp off
+
 
+
</nowiki></pre>
+
This will create a virtual interface br0.
+
Now restart networking:
+
<pre><nowiki>
+
sudo /etc/init.d/networking restart
+
</nowiki></pre>
+
=== Configuring ubuntu-vm-builder to create bridged guests by default ===
+
Virtual machines are defined in XML files; ubuntu-vm-builder, the tool we will use to create VMs, bases them on the template file /usr/share/ubuntu-vm-builder/templates/libvirt.tmpl.
+
Open that file, and change:
+
<pre><nowiki>
+
    <interface type='network'>
+
      <mac address='%MAC%'/>
+
      <source network='default'/>
+
    </interface>
+
</nowiki></pre>
+
To:
+
<pre><nowiki>
+
    <interface type='bridge'>
+
      <mac address='%MAC%'/>
+
      <source bridge='br0'/>
+
    </interface>
+
</nowiki></pre>
+
=== Converting an existing guest ===
+
If you have already created VMs before, you can make them use bridged networking if you change the XML definition (in /etc/libvirt/qemu/) for the network interface, adjusting the mac address as desired from:
+
<pre><nowiki>
+
    <interface type='network'>
+
      <mac address='00:11:22:33:44:55'/>
+
      <source network='default'/>
+
    </interface>
+
</nowiki></pre>
+
to:
+
<pre><nowiki>
+
    <interface type='bridge'>
+
      <mac address='00:11:22:33:44:55'/>
+
      <source bridge='br0'/>
+
    </interface>
+
</nowiki></pre>
+
'''Note: Make sure the first octet in your MAC address is EVEN (eg. 00:)''' as MAC addresses with ODD first-bytes (eg. 01:) are reserved for multicast communication and can cause confusing problems for you.  For instance, the guest will be able to receive ARP packets and reply to them, but the reply will confuse other machines.  This is not a KVM issue, but just the way Ethernet works.
+
You do not need to restart libvirtd to reload the changes; the easiest way is to log into virsh (a command line tool to manage VMs), stop the VM, reread its configuration file, and restart the VM:
+
<pre><nowiki>
+
yhamon@paris:/etc/libvirt/qemu$ ls
+
mirror.xml  networks  vm2.xml
+
yhamon@paris:/etc/libvirt/qemu$ virsh --connect qemu:///system
+
Connecting to uri: qemu:///system
+
Welcome to virsh, the virtualization interactive terminal.
+
 
+
Type:  'help' for help with commands
+
      'quit' to quit
+
 
+
virsh # list
+
Id Name                State
+
----------------------------------
+
10 vm2                  running
+
15 mirror              running
+
 
+
virsh # shutdown mirror
+
Domain mirror is being shutdown
+
 
+
virsh # define mirror.xml
+
Domain mirror defined from mirror.xml
+
 
+
virsh # start mirror
+
Domain mirror started
+
 
+
</nowiki></pre>
+
The VM "mirror" is now using bridged networking.
+
=== DNS and DHCP Guests ===
+
libvirt uses dnsmasq to hand out IP addresses to guests which are configured to use dhcp. If on your host machine, you add 192.168.122.1 (the default IP of your host in libvirt) as your first nameserver in /etc/resolv.conf, then you can do name resolution for your guests. dnsmasq is smart enough to use the other 'nameserver' entries in your /etc/resolv.conf for resolving non-libvirt addresses. For example, if your current /etc/resolv.conf is:<pre><nowiki>
+
search example.com
+
nameserver 10.0.0.1
+
</nowiki></pre>
+
Change this to be:<pre><nowiki>
+
search example.com
+
nameserver 192.168.122.1
+
nameserver 10.0.0.1
+
</nowiki></pre>
+
Now, if you have a virtual machine named 'hardy-amd64', after starting it, you can do: <pre><nowiki>
+
$ host hardy-amd64
+
hardy-amd64 has address <IP address given by dnsmasq>
+
</nowiki></pre>
+
Note that when using ssh you may need to use a trailing '.' after the hostname:<pre><nowiki>
+
$ ssh hardy-amd64.
+
</nowiki></pre>
+
Finally, for this to work, your guest must send its hostname as part of the dhcp request. This is done automatically on many operating systems. For systems that do not send this automatically and use dhcp3, you can adjust the dhclient.conf file. For example, on Ubuntu 6.06 LTS (Dapper), adjust /etc/dhcp3/dhclient.conf to have:<pre><nowiki>
+
send host-name "<your guest hostname here>";
+
</nowiki></pre>
+
'''IMPORTANT:''' Depending on your network configuration, your host's /etc/resolv.conf file might be periodically overwritten. You will have to either adjust the dhcp server on your network to hand out the additional libvirt name server for your libvirt hosts, or adjust each host machine accordingly. As there are many possible configurations for host machines, user's are encouraged to look at <code><nowiki>resolvconf</nowiki></code> and/or <code><nowiki>man interfaces</nowiki></code>.
+
=== Booting Over the Network Using PXE ===
+
The current Ubuntu release does not ship pxe binary ROM images because the source code is not included to recreate the images in the upstream tarball.  There may be a way to automate the creation of these files as part of the package.  In order to use boot -n, you will need to download or create the appropriate ROM images from [[http://etherboot.org]]
+
KVM and QEMU can emulate a number of network cards.  Here is the current ROM files
+
{|border="1" cellspacing="0"
+
| 'KVM Name' ''nic,model='' |||| 'Etherboot Identification' |||| 'Etherboot Filename' |||| 'KVM filename'
+
|-
+
| i82551 |||| |||| |||| pxe-i82551.bin
+
|-
+
| i82557b |||| |||| |||| pxe-i82557b.bin
+
|-
+
| i82559er |||| |||| |||| pxe-i82559er.bin
+
|-
+
| ne2k_pci (default) |||| ns8390:rtl8029 -- [10ec,8029] |||| gpxe-0.9.3-rtl8029.rom |||| pxe-ne2k_pci.bin
+
|-
+
| ne2k_isa |||| |||| |||| pxe-ne2k_isa.bin
+
|-
+
| pcnet |||| |||| |||| pxe-pcnet.bin
+
|-
+
| rtl8139 |||| |||| |||| pxe-rtl8139.bin
+
|-
+
| e1000 |||| ((e1000:e1000-0x1026 -- [8086,1026])) |||| gpxe-0.9.3-e1000-0x1026.rom |||| pxe-e1000.bin
+
|-
+
| smc91c111 |||| |||| |||| pxe-smc91c111.bin
+
|-
+
| lance |||| |||| |||| pxe-lance.bin
+
|-
+
| mcf_fec |||| |||| |||| pxe-mcf_fec.bin
+
|}
+
Copy the respective file to /usr/share/kvm and/or /usr/share/qemu.
+
== Creating virtual machines ==
+
Now that KVM is installed, let s see how we install our first VM. There is a tool to manage VMs on a remote host: virt-manager. Sadly, VM creation on a remote host is not supported yet through virt-manager - therefore you will have to create the VM in command line.
+
There are two different tools to do this; virt-install, a python script developed by Red Hat, and ubuntu-vm-builder, developed by Canonical.
+
=== Ubuntu-vm-builder: the fast & powerful way to create Ubuntu JEOS VMs ===
+
[[http://doc.ubuntu.com/ubuntu/serverguide/C/ubuntu-vm-builder.html|Ubuntu-vm-builder]] is probably the best tool to use if you want to create VMs running Ubuntu JEOS 8.04, as the install is entirely scripted (very fast).
+
This tool is packaged, and in universe:
+
<pre><nowiki>
+
sudo apt-get install ubuntu-vm-builder
+
</nowiki></pre>
+
==== Basic use ====
+
Here is a very basic example of how to use it:
+
<pre><nowiki>
+
sudo ubuntu-vm-builder kvm hardy
+
</nowiki></pre>
+
This will create an Ubuntu Hardy, with all options set to default.
+
Or you can use this URL to a Javascript tool that generates the lengthy set of parameters available for ubuntu-vm-builder:
+
* http://people.ubuntu.com/~kirkland/ubuntu-vm-builder.html
+
Note: if you want to use Virsh to manage your virtual machines as detailed below, you must add
+
<pre><nowiki>
+
--libvirt qemu:///system
+
</nowiki></pre>
+
to the list of arguments that the javascript produces. The javascript does not have an option for this itself, unfortunately.
+
==== More complex example ====
+
Now here is a somewhat more complex example:
+
<pre><nowiki>
+
ubuntu-vm-builder kvm hardy \
+
                  --domain newvm \
+
                  --dest newvm \
+
                  --arch i386 \
+
                  --hostname hostnameformyvm \
+
                  --mem 256 \
+
                  --user john \
+
                  --pass doe \
+
                  --ip 192.168.0.12 \
+
                  --mask 255.255.255.0 \
+
                  --net 192.168.0.0 \
+
                  --bcast 192.168.0.255 \
+
                  --gw 192.168.0.1 \
+
                  --dns 192.168.0.1 \
+
                  --mirror http://archive.localubuntumirror.net/ubuntu \
+
                  --components main,universe \
+
                  --addpkg vim openssh-server \
+
                  --libvirt qemu:///system ;
+
</nowiki></pre>
+
This will create a new Ubuntu Hardy VM called "newvm", the hostname will be set to "hostnameformyvm", the network will be configured with a static IP address and a gateway at address 192.168.0.1. The --mirror will tell the script to download the packages from a local Ubuntu mirror instead of the default server (this may speed up by a lot the time necessary to create the VM). The components argument will enable main and universe by default on the VM, --addpkg vim will install vim, and finally the last argument will automatically add the newly created VM to KVM.
+
By adding 'openssh-server' with --addpkg, we will be able to ssh into our new machine once its started (provided the networking works correctly).
+
Note: The manual isn't specific about the --exec option, used to execute a script file during the vm build process. If you specify the --exec option then you must provide the full path to the script you are executing. Not doing so will cause the installer to tell you that it can't find the script file.
+
'''Bug notice: ''' it seems that the package 'linux-package' is not found during the machine building process unless 'restricted' is also specified as a component option to ubuntu-vm-builder. If not specified, you'll get a non-functioning system that boots into grub only. This line makes it work for me:
+
<pre><nowiki>
+
--components 'main,universe,restricted'
+
</nowiki></pre>
+
I'm assuming this is a bug in ubuntu-vm-builder.
+
==== Install on a raw block device ====
+
Ubuntu-vm-builder doesn't allow you to create the VM on a raw block device yet (like a standalone partition, or a iSCSI share). You can use ubuntu-vm-builder to create the qcow2 image and then move the VM to the block device with qemu-img though; if /dev/sdb is the disk device on which you want to move the virtual machine:
+
<pre><nowiki>
+
sudo qemu-img convert root.qcow2 -O raw /dev/sdb
+
</nowiki></pre>
+
Edit the XML definition file for the VM in /etc/libvirt/qemu/, and set the source file to be:
+
<pre><nowiki>
+
<source file='/dev/sdb'/>
+
</nowiki></pre>
+
Redefine the VM and start it; it is now running from /dev/sdb.
+
Ubuntu-vm-builder is a very powerful tool - to get a more detailed list of its capabilities, use ubuntu-vm-builder --help.
+
=== Use virtio for Ubuntu Hardy guests ===
+
You may find the performances of the network relatively poor (approx. 100/120mbits on my servers, which are quite fast). If you are running Ubuntu Hardy, you can enable virtio. Go to the definition file of your VM, and add the virtio line to the definition of your network interface:
+
<pre><nowiki>
+
    <interface type='bridge'>
+
      <mac address='52:54:00:a0:41:92'/>
+
      <source bridge='br0'/>
+
      <model type='virtio'/>  <-- add this line, leave the rest
+
    </interface>
+
</nowiki></pre>
+
This improves the network performances by a lot (factor 10, nearly). But this works only with ubuntu hardy guests for the moment, which is why it is not by default.
+
=== Create VMs running other operating systems: virt-install ===
+
Virt-install is radically different in the way it works. Instead of creating automagically a new VM, it will allow you to boot on an iso, and therefore to install almost any operating system.  For a list of supported operating system, consult [[http://kvm.qumranet.com/kvmwiki/Guest_Support_Status|kvm's official webpage]].
+
==== Example Windows install ====
+
{{http://waste.mandragor.org/windows-kvm.png}}
+
Copy the ISO of the system you want to install to your working directory:
+
<pre><nowiki>
+
yhamon@paris:~$ ls *.iso
+
ubuntu-8.04-server-i386.iso  windowsxpsp2.iso
+
</nowiki></pre>
+
or create an ISO from a cd/dvd:
+
<pre><nowiki>
+
dd if=/dev/dvd of=dvd.iso
+
</nowiki></pre>
+
Install virt-install:
+
<pre><nowiki>
+
sudo apt-get install python-virtinst
+
</nowiki></pre>
+
Then, run virt-install (the install of windows XP doesn't work when accelerated with --accelerate, so run the install and then replace qemu by kvm in the XML file once installed):
+
<pre><nowiki>
+
sudo virt-install --connect qemu:///system -n xpsp2 -r 512 -f windows.qcow2 -s 12 -c windowsxpsp2.iso --vnc --noautoconsole --os-type windows --os-variant winxp
+
</nowiki></pre>
+
This will boot a new VM from the ISO. Connect to the new VM using virt-viewer:
+
<pre><nowiki>
+
virt-viewer -c qemu:///system xpsp2
+
</nowiki></pre>
+
Or if KVM is running on a different server:
+
<pre><nowiki>
+
virt-viewer -c qemu+ssh://ip/system xpsp2
+
</nowiki></pre>
+
You should now have a graphical interface to install your VM!
+
==== Example Ubuntu install ====
+
You can perform the following to install Ubuntu Hardy:<pre><nowiki>
+
sudo virt-install --connect qemu:///system -n hardy -r 512 -f hardy.qcow2 -s 12 -c hardy-server-amd64.iso --vnc --noautoconsole --os-type linux --os-variant ubuntuHardy --accelerate --network=network:default
+
</nowiki></pre>
+
The '--network' option sets up the machine to use the default libvirt network. You can see available libvirt networks with:<pre><nowiki>
+
virsh net-list --all
+
</nowiki></pre>
+
==== Other Operating Systems ====
+
Other Operating Systems can be installed using the same method as above. See 'man virt-install' for more information on different options for your virtual machine and supported OS types and OS variants.
+
'''Warning:''' this method fails with Fedora [[UbuntuHelp:LiveCD|LiveCD]] installations and possibly others; see the bug here: https://bugs.launchpad.net/ubuntu/+source/kvm/+bug/220463
+
=== Cloning a virtual machine ===
+
You can clone an existing virtual machine using the virt-clone tool.  This duplicates the disk image and sets up the virtual machine domain configuration.
+
If you wish to clone a virtual machine named ''srchost'' to a new machine ''newhost'', ensure that the virtual machine ''srchost'' is not running and execute the following command.
+
<pre><nowiki>
+
$ virt-clone --connect=qemu:///system -o srchost -n newhost -f /path/to/newhost.qcow2
+
</nowiki></pre>
+
== Manage your virtual machines ==
+
=== From the shell ===
+
You can manage your VMs from the shell using [[http://linux.die.net/man/1/virsh|virsh]]. You can get a list of the available commands if you type "help". Type "help command" to get additional infos for a particular command.
+
==== Define your new VM ====
+
Before you can manage your new VM with virsh, you must define it:
+
<pre><nowiki>
+
$ virsh --connect qemu:///system
+
Connecting to uri: qemu:///system
+
Welcome to virsh, the virtualization interactive terminal.
+
 
+
Type:  'help' for help with commands
+
      'quit' to quit
+
 
+
virsh # define /etc/libvirt/qemu/newvm.xml
+
Domain newvm defined from /etc/libvirt/qemu/newvm.xml
+
</nowiki></pre>
+
Note that to list newvm, you must use 'list --inactive' or 'list --all', since list without any options will only list currently running machines.
+
==== List your VMs ====
+
Virsh allows you to list the virtual machines available on the current host:
+
<pre><nowiki>
+
yhamon@paris:/etc/libvirt/qemu$ virsh --connect qemu:///system
+
Connecting to uri: qemu:///system
+
Welcome to virsh, the virtualization interactive terminal.
+
 
+
Type:  'help' for help with commands
+
      'quit' to quit
+
 
+
virsh # help list
+
  NAME
+
    list - list domains
+
 
+
  SYNOPSIS
+
    list [--inactive | --all]
+
 
+
  DESCRIPTION
+
    Returns list of domains.
+
 
+
  OPTIONS
+
    --inactive      list inactive domains
+
    --all            list inactive & active domains
+
 
+
virsh # list
+
Id Name                State
+
----------------------------------
+
15 mirror              running
+
16 vm2                  running
+
 
+
virsh # list --all
+
Id Name                State
+
----------------------------------
+
15 mirror              running
+
16 vm2                  running
+
  - test5                shut off
+
</nowiki></pre>
+
==== Define, undefine, start, shutdown, destroy VMs ====
+
The VMs you see with list --all are VMs that have been "defined" from an XML file. Every VM is configured via a XML file in /etc/libvirt/qemu. If you want to remove a VM from the list of VMs, you need to undefine it:
+
<pre><nowiki>
+
virsh # undefine test5  # WARNING: undefine will delete your XML file!
+
Domain test5 has been undefined
+
 
+
virsh # list --all
+
Id Name                State
+
----------------------------------
+
15 mirror              running
+
16 vm2                  running
+
</nowiki></pre>
+
To be able to undefine a virtual machine, it needs to be shutdown first:
+
<pre><nowiki>
+
virsh # shutdown mirror
+
Domain mirror is being shutdown
+
</nowiki></pre>
+
This command asks for a nice shutdown (like running shutdown in command line) - but you can also use "destroy", the more brutal way of shutting down a VM, equivalent of taking the power cable off:
+
<pre><nowiki>
+
virsh # destroy mirror
+
Domain mirror destroyed
+
</nowiki></pre>
+
If you have made a change to the XML configuration file, you need to tell KVM to reload it before restarting the VM:
+
<pre><nowiki>
+
virsh # define /etc/libvirt/qemu/mirror.xml
+
Domain mirror defined from /etc/libvirt/qemu/mirror.xml
+
</nowiki></pre>
+
Then, to restart the VM:
+
<pre><nowiki>
+
virsh # start mirror
+
Domain mirror started
+
</nowiki></pre>
+
==== Suspend and resume a Virtual Machine ====
+
Virsh allows you to easily suspend and resume a virtual machine.
+
<pre><nowiki>
+
virsh # suspend mirror
+
Domain mirror suspended
+
 
+
virsh # resume mirror
+
Domain mirror resumed
+
</nowiki></pre>
+
=== Using a graphical interface ===
+
There is also an easier way to manage your virtual machines. The tool virt-manager allows you to use a graphical interface to interact with KVM. Install virt-manager on your desktop:
+
<pre><nowiki>
+
sudo apt-get install virt-manager virt-viewer
+
</nowiki></pre>
+
And use it to connect to your server:
+
<pre><nowiki>
+
$ virt-manager -c qemu+ssh://10.10.10.10/system
+
</nowiki></pre>
+
10.10.10.10 being the IP address of your host running KVM.
+
{{http://waste.mandragor.org/virt-manager-screenshot.png}}
+
If you are only managing machines on your own host you can use only:
+
<pre><nowiki>
+
$ virt-manager -c qemu:///system
+
</nowiki></pre>
+
== Editing the attributes of a Virtual Machine ==
+
libvirt stores it's configuration as xml in '/etc/libvirt/qemu'. The xml is easy to understand, and is similar to [[UbuntuHelp:VMware|VMware]] *.vmx files. While it is possible to edit these files in place and restart libvirt-bin for the changes to take affect, the recommended method for modifying the attributes of a virtual machine is via virsh (or virt-manager, if it supports changing the hardware you want to change). The concept is simple:
+
<ol><li>export (aka 'dump') the xml of the virtual machine you want to edit
+
</li><li>edit the xml
+
</li><li>import (aka 'define') the xml</li></ol>
+
 
+
For example, to edit the machine named 'foo' (you can get a list of your machines with 'virsh list --all'), do:<pre><nowiki>
+
$ virsh dumpxml foo > /tmp/foo.xml
+
(edit /tmp/foo.xml as needed)
+
$ virsh define /tmp/foo.xml
+
</nowiki></pre>
+
=== Adding CPUs ===
+
KVM allows you to create SMP guests. To allocate two CPUs to a VM, dump the xml as above, then edit your xml to have:<pre><nowiki>
+
<domain type='kvm'>
+
  ...
+
  <vcpu>2</vcpu>
+
  ...
+
</domain>
+
</nowiki></pre>
+
Now define the VM as above.
+
=== Adding Memory ===
+
To change the memory allocation in a VM, dump the xml as above, then edit your xml to have:<pre><nowiki>
+
<domain type='kvm'>
+
  ...
+
  <memory>262144</memory>
+
  <currentMemory>262144</currentMemory>
+
  ...
+
</domain>
+
</nowiki></pre>
+
Now define the VM as above.  Keep in mind that the memory allocation is in kilobytes, so to allocate 512MB of memory, use 512 * 1024, or 524288.
+
=== Changing the Network Card Model ===
+
kvm and qemu currently default to using the rtl8139 NIC. Supported NICs in Ubuntu 8.04 LTS are i82551, i82557b, i82559er, ne2k_pci, pcnet, rtl8139, e1000, and virtio. To use an alternate NIC, dump the xml as above, then edit your xml to have:<pre><nowiki>
+
<domain type='kvm'>
+
  ...
+
    <interface type='network'>
+
      ...
+
      <model type='e1000'/>
+
    </interface>
+
  ...
+
</domain>
+
</nowiki></pre>
+
Now define the VM as above.
+
=== Get new IDs ===
+
To get a new mac address to paste into your xml file, use this command:
+
MACADDR="52:54:$(dd if=/dev/urandom count=1 2>/dev/null | md5sum | sed 's/^\(..\)\(..\)\(..\)\(..\).*$/\1:\2:\3:\4/')"; echo $MACADDR
+
To get a new uuid for your xml file, use: uuidgen
+
== KVM from the command line ==
+
KVM is very similar to qemu and it is possible to run machines from the command line. The basic syntax is :
+
<pre><nowiki>
+
kvm -m 512 -hda disk.img -cdrom ubuntu.iso -boot d -smp 2
+
</nowiki></pre>
+
* -m = memory (in MB)
+
* -hda = first hard drive
+
* You can use a number of image file types including .img, .cow
+
* You can also boot a hard drive. '''Be careful with this option as you do not want to boot the host root partition'''
+
* Syntax -hda /dev/sda
+
* This will call your grub menu from your MBR when you boot kvm.
+
* -cdrom can be an iso image or a CD/DVD drive.
+
* -boot [a|c|d|n] boot on floppy (a), hard disk (c), CD-ROM (d), or network (n)
+
* -smp = number of CPU
+
* -alt-grab change Ctrl-Alt mouse grab combination for Ctrl-Alt-Shift (very practical if you often use some control key combinations like Ctrl-Alt-Del or Windows-E)
+
There are a number of additional options and additional help is available with :
+
<pre><nowiki>
+
kvm --help
+
</nowiki></pre>
+
=== Bridged Networking ===
+
In order to run KVM using bridged networking as a user we need to perform some configuration.
+
1. First bridge your network card as above [[UbuntuHelp:KVM#Creating_a_network_bridge_on_the_host|| Creating a network bridge on the host]]
+
2. Install uml-utilities
+
 
+
<pre><nowiki>
+
sudo apt-get install uml-utilities
+
</nowiki></pre>
+
3. Set permissions on your tun device. Using any editor, edit ''/etc/udev/rules.d/40-permissions.rules'', add this line at the bottom of the file :
+
 
+
<pre><nowiki>
+
KERNEL=="tun", GROUP="kvm", MODE="0660"
+
</nowiki></pre>
+
4. Reboot (to bring up your bridge and tun device).
+
5. Edit ''/etc/kvm/kvm-ifup'' adding sudo in front of the ifconfig and brctl commands
+
 
+
<pre><nowiki>
+
#!/bin/sh
+
 
+
switch=$(ip route ls | awk '/^default / { for(i=0;i<NF;i++) { if ($(i) == "dev") print $(i+1) }}')
+
'''sudo''' /sbin/ifconfig $1 0.0.0.0 up
+
'''sudo''' /usr/sbin/brctl addif ${switch} $1
+
exit 0
+
</nowiki></pre>
+
6. We need a wrapper script for launching kvm. I put this script in ~/bin and call it '''kvm-bridge'''. If ~/bin is on your path you can call the command directly with '''kvm-bridge'''. This script was modified from a number of sources
+
 
+
<pre><nowiki>
+
#!/usr/bin/env bash
+
# script to manage tap interface allocation
+
# for linux kernels >= 2.6.18
+
 
+
# modified by bodhi.zazen from :
+
# http://calamari.reverse-dns.net:980/cgi-bin/moin.cgi/FrequentlyAskedQuestions#head-2511814cb92c14dbe1480089c04f83c281117a86
+
# http://ubuntuforums.org/showthread.php?t=528046
+
# http://www.howtoforge.com/using-kvm-on-ubuntu-gutsy-gibbon
+
 
+
# set up a tap interface for qemu
+
# USERID - uid qemu is being run under.
+
USERID=`whoami`
+
 
+
# generate a random mac address for the qemu nic
+
# shell script borrowed from user pheldens @ qemu forum
+
 
+
ranmac=$(echo -n DE:AD:BE:EF ; for i in `seq 1 2` ; \
+
do echo -n `echo ":$RANDOM$RANDOM" | cut -n -c -3` ;done)
+
 
+
# specify which NIC to use - see qemu.org for others
+
# model=r8169
+
# Set model based on this how-to
+
# http://www.howtoforge.com/using-kvm-on-ubuntu-gutsy-gibbon
+
 
+
model=rtl8139
+
iface=`sudo tunctl -b -u $USERID`
+
 
+
# start kvm with our parameters
+
# echo "Bringing up interface $iface with mac address $ranmac"
+
# nohup added to allow kvm to run independent of the terminal
+
nohup kvm -net nic,vlan=0,macaddr=$ranmac -net tap,vlan=0,ifname=$iface $@
+
 
+
# kvm has stopped - no longer using tap interface
+
sudo tunctl -d $iface &> /dev/null
+
</nowiki></pre>
+
7. Set the executable bit on the new script you just created:
+
 
+
<pre><nowiki>
+
chmod 0755 ~/bin/kvm-bridge
+
</nowiki></pre>
+
8. Modify sudoers to allow members of the kvm group to run the wrapper kvm-bridge and create a bridged network interface without running KVM as root.
+
 
+
<pre><nowiki>
+
visudo
+
</nowiki></pre>
+
Add these line at the end of the file :
+
<pre><nowiki>
+
# Allow members of the kvm group to configure a bridged virtual network interface
+
%kvm ALL=(ALL) NOPASSWD: /sbin/ifconfig, /usr/sbin/brctl, /usr/sbin/tunctl
+
</nowiki></pre>
+
9. Now start kvm from the command line. '''You do not need to declare a network interface'''
+
 
+
<pre><nowiki>
+
kvm-bridge -m 512 -hda disk.img -cdrom ubuntu.iso -boot -d -smp 2
+
</nowiki></pre>
+
=== iptables ===
+
Add these rules to iptables :
+
<pre><nowiki>
+
# allow incoming packets for kvm guest
+
IPTABLES -A FORWARD -d $IPADDR_FROM_GUEST_OS -j ACCEPT
+
# allow outgoing packets from kvm
+
IPTABLES -A FORWARD -s $IPADDR_FROM_GUEST_OS -j ACCEPT
+
</nowiki></pre>
+
Change "$IPADDR_FROM_GUEST_OS" to the actual ip address of the kvm guest (I advise you configure your guests to have a static IP address).
+
If you use ufw, add these rules to ''/etc/ufw/before.rules''
+
* See [[https://help.ubuntu.com/8.04/serverguide/C/firewall.html | Ubuntu Server Guide Firewall]]
+
== Troubleshooting/FAQ ==
+
=== Virtualbox and KVM ===
+
Installing kvm loads the module kvm (or kvm-intel in my case) which does not allow other virtualization software to run, e.g. virtualbox. See [[UbuntuHelp:KVM#head-e46c0245ab3a34e43db63059478fa1a68d18128f|Removal|section]] to set this straight :)
+
=== How to boot Dapper, Edgy, Feisty or Gutsy ISO ===
+
* Q: I'm on Intel hardware, and I'm trying to boot Dapper, Edgy, Feisty, or Gutsy, but kvm fails immediately.
+
* A: Yes, this is rather unfortunate. The issue is a limitation in Intel's virtualisation extensions that don't interact very well with gfxboot. The evil, hacky workaround is to modify the ISO to disable gfxboot. The following has worked for me, but it might kill your cat or make your coffee go cold or make other unpleasantries happen to you. You've been warned!
+
<pre><nowiki>
+
$ sed -e 's/GFXBOOT bootlogo/#FXBOOT bootlogo/g' < ubuntu-7.10-server-amd64.iso > ubuntu-7.10-server-amd64-nogfxboot.iso
+
</nowiki></pre>
+
/!\ Don't change the above command! The length of the string mustn't change or you will have knackered the filesystem on the CD.
+
A slightly safer way is to download gfxboot-disable from [[http://hg.codemonkey.ws/gfxboot-disable]] and then run:
+
<pre><nowiki>
+
$ gfxboot-disable ubuntu-7.10-server-amd64.iso
+
</nowiki></pre>
+
=== Boot a VM into single mode ===
+
A VM has a complete BIOS, and also runs GRUB. Bad point is, it disappears after a couple of seconds, most of the time you won't even have time to connect using virt-viewer. There is a small trick here: shutdown the VM, run virt-viewer with the argument --wait (that way it will wait for the VM to start and pop up directly after that), and then start the VM; this should give you a good 2 seconds time to enter the bios or access grub.
+
If you are running a VM built with ubuntu-vm-builder, there is a small bug that will prevent you from logging in; in grub, select the recovery line and press "e"; select the line beginning with kernel, press "e" again. At the end of the line, add "init=/bin/sh" (without the quotes). Confirm with enter, and press b to boot the kernel with these settings.
+
=== How to convert [[UbuntuHelp:VMware|VMware]] machines to virt-manager ===
+
kvm has the ability to use [[UbuntuHelp:VMware|VMware]]'s vmdk disk files directly, as long as the disk is wholly contained in the vmdk (ie [[UbuntuHelp:VMware|VMware]] allows splitting a disk into smaller, usually 2GB, vmdk files. kvm can't use these). Point kvm at the vmdk with the appropriate options (see <code><nowiki> man kvm-qemu </nowiki></code>), and it should work.
+
To use the [[UbuntuHelp:VMware|VMware]] machine from within virt-manager, the .vmx file must be converted to libvirt's .xml. vmware2libvirt was created to help with this, and it can be used like so:
+
<pre><nowiki>
+
$ vmware2libvirt -f ./file.vmx > file.xml
+
$ virsh -c qemu:///system define file.xml
+
</nowiki></pre>
+
The first command converts the [[UbuntuHelp:VMware|VMware]] 'file.vmx' file to the libvirt compatible 'file.xml'. See <code><nowiki> man vmware2libvirt </nowiki></code> for details. '''Note:''' until vmware2libvirt is shipped with the libvirt packages, you can download it from [[http://people.ubuntu.com/~soren/vmware2libvirt/]]. The second command imports file.xml into libvirt. The imported .xml files are stored in /etc/libvirt/qemu.
+
'''IMPORTANT:''' keep in mind that while the .vmx file is converted to .xml, the disks are used as is. Please make backups, especially if you want to use the virtual machine in [[UbuntuHelp:VMware|VMware]] later.
+
==== Caveats ====
+
While vmware2libvirt works well on simple virtual machines, there are limitations because .vmx files don't always contain enough information, and also because vmware2libvirt tries not to make too many assumptions about what it finds. A couple of things to look out for:
+
<ol><li>While vmware2libvirt attempts to detect a 64-bit guest, be sure that your 64-bit guest has in its .xml file: <pre><nowiki>
+
<os>
+
<type arch='x86_64' machine='pc'>hvm</type>
+
...
+
</os>
+
</nowiki></pre>
+
</li><li>vmware2libvirt only detects and uses the first ethernet interface found. Additional interfaces can be added from within virt-manager.
+
</li><li>Currently the first scsi disk is used if found, otherwise the first ide disk. Additional disks can be added from within virt-manager.
+
</li><li>The converted virtual machine is hard-coded to use 1 cpu.  This can be changed with:<pre><nowiki>
+
<vcpu>2</vcpu>
+
</nowiki></pre>
+
</li><li>vmware2libvirt does not (and cannot) convert anything that was VMware-specific within the guest. See 'Guest Notes' below for more details.</li></ol>
+
 
+
=== Guest notes ===
+
<ol><li>If converting from vmware to libvirt, be sure to remove vmware-tools if you have it installed (otherwise it will overwrite xorg.conf on reboot)
+
</li><li>Guests should not use ntp to synchronize the clock, so be sure to remove/disable ntpd
+
</li><li>Linux guests with Xorg should be using the 'cirrus' video driver.  To use, adjust /etc/X11/xorg.conf to have: <pre><nowiki>
+
Section "Device"
+
        Identifier      "Configured Video Device"
+
        Driver          "cirrus"
+
EndSection
+
</nowiki></pre> then be sure that your Screen section uses 'Configured Video Device' for its Device.
+
</li><li>Linux guests with Xorg should be using the 'vmmouse' driver (not available on Ubuntu Dapper).  To use, perform within the guest: <pre><nowiki>
+
aptitude install xserver-xorg-input-vmmouse
+
</nowiki></pre> then adjust /etc/X11/xorg.conf to have (the Identifier line should not change, and you should have only an Identifier line and Driver line for the mouse): <pre><nowiki>
+
Section "InputDevice"
+
        Identifier      "Configured Mouse"
+
        Driver          "vmmouse"
+
EndSection
+
</nowiki></pre>
+
</li><li>Linux guests with Xorg need to adjust the resolution for Xorg in /etc/X11/xorg.conf.  Look for the Screen section, and make sure each of the 'Modes' lines has a reasonable resolution for your system (due to [[https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/193456|bug #193456]] the resolution in the guest's resolution needs to be smaller than the host). Eg: <pre><nowiki>
+
Section "Screen"
+
        ...
+
        SubSection "Display"
+
                Depth          16
+
                Modes          "800x600" "640x480"
+
        EndSubSection
+
        SubSection "Display"
+
                Depth          24
+
                Modes          "800x600" "640x480"
+
        EndSubSection
+
EndSection
+
</nowiki></pre>
+
</li><li>Windows (other than Vista) virtual machines should substitute in the .xml file: <pre><nowiki>
+
<features>
+
  <acpi/>
+
</features>
+
</nowiki></pre> with: <pre><nowiki>
+
<features/>
+
</nowiki></pre>
+
</li><li>Windows Vista virtual machines should add this to the xml file: <pre><nowiki>
+
<domain type='kvm'>
+
...
+
  <features>
+
    <acpi/>
+
  </features>
+
</domain>
+
</nowiki></pre>
+
</li><li>Debian Sarge (oldstable) may write /boot/grub/menu.lst incorrectly, resulting in the following on boot: <pre><nowiki>
+
pivot_root: no such file or directory
+
/sbin/init: 432: cannot open dev/console: no such file
+
Kernel panic: Attempted to kill init!
+
</nowiki></pre> The fix is at the grub menu, press 'e' and adjust <code><nowiki>root=/dev/hdb1</nowiki></code> to be <code><nowiki>root=/dev/hda1</nowiki></code>. After a successful boot, you will need to update /boot/grub/menu.lst to have: <pre><nowiki>
+
# kopt=root=/dev/hda1 ro
+
</nowiki></pre> and run: <pre><nowiki>
+
# update-grub
+
</nowiki></pre>
+
</li><li>OpenBSD 4.1 (and probably others) when using the rtl8139 network driver may realize poor network performance and see this message on the console:<pre><nowiki>
+
re0: watchdog timeout
+
</nowiki></pre> The fix is to use another NIC (e1000 appears to work well). See 'Changing the Network Card Model' above.</li></ol>
+
 
+
== Removing KVM ==
+
Removing kvm is pretty easy:<pre><nowiki>
+
# sudo apt-get remove --purge kvm
+
</nowiki></pre>
+
But kvm-intel or kvm module will still be loaded, to remove it completely and stop kvm modules from loading automatically on each boot:<pre><nowiki>
+
# sudo rm -rf /etc/kvm/ /etc/udev/rules.d/45-kvm.rules /etc/init.d/kvm
+
</nowiki></pre>
+
 
----
 
----
 
[[category:CategoryVirtualization]]
 
[[category:CategoryVirtualization]]
  
 
[[category:UbuntuHelp]]
 
[[category:UbuntuHelp]]

2010年5月19日 (三) 23:05的最新版本

  1. title The Kernel Virtual Machine

Introduction

Ubuntu uses KVM as the backend virtualisation technology and libvirt as its toolkit/API. Libvirt frontends for managing VMs include virt-manager (GUI) or virsh (CLI). Alternative management options include convirt (GUI) or convirt2 (WWW).

Documentation

  • Installation - Installation and removal of KVM
  • Networking - Network configuration; includes bridging
  • Guest Creation - Creation of different kinds of guests
  • Guest Management - Management of guests; command line or graphically
  • KVM Directly - Using KVM directly (without libvirt)
  • FAQ - Frequently asked questions, troubleshooting tips and other recommendations

Notes

  • The previous version of this page (which was documenting KVM for Feisty) has been moved to KVMFeisty
  • Also checkout the official docs, http://doc.ubuntu.com/ubuntu/serverguide/C/virtualization.html
  • The use case targeted when KVM was moved into main is "server virtualization". This means that even though KVM can be used to serve other purposes, it has been designed to be run on Ubuntu Server Edition to host non-graphical server operating systems. If you are looking for software to serve graphically-based virtual machines, VirtualBox, Parallels Workstation (or Parallels Desktop for Mac), or VMware Player/Server are more suitable alternatives.