Manage your virtual machines

From the GUI

There are several methods from the GUI, but the easiest to set up is probably VirtManager. See the setup guide at the above link. Alternative management options include convirt (GUI) or convirt2 (WWW).

From the shell

You can manage your VMs from the shell using 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:

$ 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

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:

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

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:

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

To be able to undefine a virtual machine, it needs to be shutdown first:

virsh # shutdown mirror
Domain mirror is being shutdown

This command asks for a nice shutdown (like running shutdown in command line).

Notice: Ubuntu 10.04 server doesn't have acpid installed by default. This package needs to be installed on the guest OS before it will listen to any requests from the host.

You can also use "destroy", the more brutal way of shutting down a VM, equivalent of taking the power cable off:

virsh # destroy mirror
Domain mirror destroyed

If you have made a change to the XML configuration file, you need to tell KVM to reload it before restarting the VM:

virsh # define /etc/libvirt/qemu/mirror.xml
Domain mirror defined from /etc/libvirt/qemu/mirror.xml

Then, to restart the VM:

virsh # start mirror
Domain mirror started

Suspend and resume a Virtual Machine

Virsh allows you to easily suspend and resume a virtual machine.

virsh # suspend mirror
Domain mirror suspended

virsh # resume mirror
Domain mirror resumed

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 VMware *.vmx files. While it is possible to edit these files in place and restart libvirt-bin for the changes to take effect, 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:

  1. export (aka 'dump') the xml of the virtual machine you want to edit
  2. edit the xml
  3. import (aka 'define') the xml

For example, to edit the machine named 'foo' (you can get a list of your machines with 'virsh list --all'), do:

$ virsh dumpxml foo > /tmp/foo.xml
(edit /tmp/foo.xml as needed)
$ virsh define /tmp/foo.xml

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:

<domain type='kvm'>
  ...
  <vcpu>2</vcpu>
  ...
</domain>

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:

<domain type='kvm'>
  ...
  <memory>262144</memory>
  <currentMemory>262144</currentMemory>
  ...
</domain>

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:

<domain type='kvm'>
  ...
    <interface type='network'>
      ...
      <model type='e1000'/>
    </interface>
  ...
</domain>

Now define the VM as above.

Adding USB Device Pass-through

Limitations

  • USB protocol 1.1 only
  • Device must be plugged in before KVM starts
  • Apparmor modifications needed

Apparmor Modification

In order for a software program to access the usb device correctly the apparmor must be changed. Edit /etc/apparmor.d/abstractions/libvirt-qemu and uncomment some lines.:

# WARNING: uncommenting these gives the guest direct access to host hardware.
# This is required for USB pass through but is a security risk. You have been
# warned.
/sys/bus/usb/devices/ r,
/sys/devices/*/*/usb[0-9]*/** r,
/dev/bus/usb/*/[0-9]* rw,

After making the changes apparmor must be restarted.:

$ sudo /etc/init.d/apparmor restart

Saucy released with a version of libvirt-bin and qemu that requires a different apparmor setting until a bug is fixed. From https://bugs.launchpad.net/ubuntu/saucy/+source/libvirt/+bug/1245251 use the following settings in /etc/apparmor.d/abstractions/libvirt-qemu:

  /dev/bus/usb/ r,
  /etc/udev/udev.conf r,
  /sys/bus/ r,
  /sys/class/ r,

After making the changes apparmor must be restarted.:

$ sudo /etc/init.d/apparmor restart

Adding USB devices

This can also be done via virt-manager.

First find the usb Vendor ID and Product ID.:

$ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 012: ID 0a5c:2110 Broadcom Corp. Bluetooth Controller
Bus 005 Device 003: ID 0483:2016 SGS Thomson Microelectronics Fingerprint Reader
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

In the event that the Broadcom Corp. Bluetooth Controller wans to be selected the vendor and product ids are 0a5c and 2110 respectively. These can be entered into the xml profile. This can be done through virsh through the edit <domain> command.:

<domain type='kvm'>
  <name>windowsxp</name>
  <devices>
    <hostdev mode='subsystem' type='usb'>
      <source>
        <vendor id='0x0a5c'/>
        <product id='0x2110'/>
      </source>
    </hostdev>
  </devices>
</domain>

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


CategoryVirtualization

KVM/Managing (last edited 2016-04-10 18:21:15 by leesharp)