1. libvirt https://help.ubuntu.com/8.04/serverguide/C/libvirt.html
Official Documentation
Ubuntu Documentation > Ubuntu 8.04 LTS > Ubuntu Server Guide > Virtualization > libvirt
libvirt
The libvirt library is used to interface with different virtualization technologies. Before getting started with libvirt it is best to
make sure your hardware supports the necessary virtualization extensions for KVM. Enter the following from a terminal
prompt:
egrep '(vmx|svm)' /proc/cpuinfo
If nothing is printed, it means that your cpu does not support hardware virtualization.
On most computer whose processor supports virtualization, it is necessary to activate an option in
the bios to enable it. The method described above does not show the status of it's activation.
Virtual 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.
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. To setup a bridge interface edit /etc/network/interfaces and either comment or replace the existing
config with:
auto lo
iface lo inet loopback
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
Enter the appropriate values for your physical interface and network.
Now restart networking and your virtual machines that are managed by libvirt will appear on the network the same as
physical hosts:
sudo /etc/init.d/networking restart
If setting up a bridge interface using Ubuntu Desktop Edition, or if dhcdbd is installed, the dhcdbd daemon will need to be
stopped and disabled.
After configuring the bridge in /etc/network/interfaces, shutdown dhcdbd by:
sudo /etc/init.d/dhcdbd stop
Now to disable it from starting on boot enter:
sudo update-rc.d -f dhcdbd remove
Installation
To install the necessary packages, from a terminal prompt enter:
sudo apt-get install kvm libvirt-bin
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2. libvirt https://help.ubuntu.com/8.04/serverguide/C/libvirt.html
After installing libvirt-bin, the user used to manage virtual machines will need to be added to the libvirtd group. Doing so will
grant the user access to the advanced networking options.
In a terminal enter:
sudo adduser $USERNAME libvirtd
If the user chosen is the current user, you will need to log out and back in for the new group
membership to take effect.
You are now ready to install a Guest operating system. Installing a virtual machine follows the same process as installing the
operating system directly on the hardware. You either need a way to automate the installation, or a keyboard and monitor will
need to be attached to the physical machine.
In the case of virtual machines a Graphical User Interface (GUI) is analogous to using a physical keyboard and mouse.
Instead of installing a GUI the virt-viewer application can be used to connect to a virtual machine's console using VNC. See
the section called “Virtual Machine Viewer” for more information.
There are several ways to automate the Ubuntu installation process, for example using preseeds, kickstart, etc. Refer to the
Ubuntu Installation Guide for details.
Yet another way to install an Ubuntu virtual machine is to use ubuntu-vm-builder. ubuntu-vm-builder allows you to setup
advanced partitions, execute custom post-install scripts, etc. For details see the section called “ubuntu-vm-builder”
virt-install
virt-install is part of the python-virtinst package. To install it, from a terminal prompt enter:
sudo apt-get install python-virtinst
There are several options available when using virt-install. For example:
sudo virt-install -n web_devel -r 256 -f web_devel.img -s 4 -c jeos.iso --accelerate --vnc --noautoconsole
-n web_devel: the name of the new virtual machine will be web_devel in this example.
-r 256: specifies the amount of memory the virtual machine will use.
-f web_devel.img: indicates the path to the virtual disk which can be a file, partition, or logical volume. In this example
a file named web_devel.img.
-s 4: the size of the virtual disk.
-c jeos.iso: file to be used as a virtual CDROM. The file can be either an ISO file or the path to the host's CDROM
device.
--accelerate: enables the kernel's acceleration technologies.
--vnc: exports the guest's virtual console using VNC.
--noautoconsole: will not automatically connect to the virtual machine's console.
After launching virt-install you can connect to the virtual machine's console either locally using a GUI or with the virt-view er
utility.
virt-clone
The virt-clone application can be used to copy one virtual machine to another. For example:
sudo virt-clone -o web_devel -n database_devel -f /path/to/database_devel.img --connect=qemu:///system
-o: original virtual machine.
-n: name of the new virtual machine.
-f: path to the file, logical volume, or partition to be used by the new virtual machine.
--connect: specifies which hypervisor to connect to.
Also, use -d or --debug option to help troubleshoot problems with virt-clone.
Replace web_devel and database_devel with appropriate virtual machine names.
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3. libvirt https://help.ubuntu.com/8.04/serverguide/C/libvirt.html
Virtual Machine Management
virsh
There are several utilities available to manage virtual machines and libvirt. The virsh utility can be used from the command
line. Some examples:
To list running virtual machines:
virsh -c qemu:///system list
To start a virtual machine:
virsh -c qemu:///system start web_devel
Similarly, to start a virtual machine at boot:
virsh -c qemu:///system autostart web_devel
Reboot a virtual machine with:
virsh -c qemu:///system reboot web_devel
The state of virtual machines can be saved to a file in order to be restored later. The following will save the virtual
machine state into a file named according to the date:
virsh -c qemu:///system save web_devel web_devel-022708.state
Once saved the virtual machine will no longer be running.
A saved virtual machine can be restored using:
virsh -c qemu:///system restore web_devel-022708.state
To shutdown a virtual machine do:
virsh -c qemu:///system shutdown web_devel
A CDROM device can be mounted in a virtual machine by entering:
virsh -c qemu:///system attach-disk web_devel /dev/cdrom /media/cdrom
In the above examples replace web_devel with the appropriate virtual machine name, and
web_devel-022708.state with a descriptive file name.
Virtual Machine Manager
The virt-manager package contains a graphical utility to manage local and remote virtual machines. To install virt-manager
enter:
sudo apt-get install virt-manager
Since virt-manager requires a Graphical User Interface (GUI) environment it is recommended to be installed on a
workstation or test machine instead of a production server. To connect to the local libvirt service enter:
virt-manager -c qemu:///system
You can connect to the libvirt service running on another host by entering the following in a terminal prompt:
virt-manager -c qemu+ssh://virtnode1.mydomain.com/system
The above example assumes that SSH connectivity between the management system and
virtnode1.mydomain.com has already been configured, and uses SSH keys for authentication. SSH
keys are needed because libvirt sends the password prompt to another process. For details on
configuring SSH see the section called “OpenSSH Server”
Virtual Machine Viewer
The virt-viewer application allows you to connect to a virtual machine's console. virt-view er does require a Graphical User
Interface (GUI) to interface with the virtual machine.
To install virt-viewer from a terminal enter:
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4. libvirt https://help.ubuntu.com/8.04/serverguide/C/libvirt.html
sudo apt-get install virt-viewer
Once a virtual machine is installed and running you can connect to the virtual machine's console by using:
virt-viewer qemu:///system web_devel
Similar to virt-manager, virt-viewer can connect to a remote host using SSH with key authentication, as well:
virt-viewer -c qemu+ssh://virtnode1.mydomain.com/system web_devel
Be sure to replace web_devel with the appropriate virtual machine name.
If configured to use a bridged network interface you can also setup SSH access to the virtual machine. See the section
called “OpenSSH Server” and the section called “Virtual Networking” for more details.
Resources
See the KVM home page for more details.
For more information on libvirt see the libvirt home page
The Virtual Machine Manager site has more information on virt-manager development.
Also, stop by the #ubuntu-virt IRC channel on freenode to discuss virtualization technology in Ubuntu.
Chapter 17. Virtualization ubuntu-vm-builder
The material in this document is available under a free license, see Legal for details
For information on contributing see the Ubuntu Documentation Team wiki page. To report a problem, visit the bug page for Ubuntu Documentation
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