Getting started with virtualization

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This page deals with using Fedora to host virtual guests. For information on using Fedora as a virtual guest, see Installing a Fedora Virtual Machine. For information the different virtualization technologies available in Fedora, see the dedicated page.

Using virtualization on Fedora

Fedora uses the libvirt family of tools as its virtualization solution. By default libvirt on Fedora will use Qemu to run guest instances.

For information on other virtualization platforms, refer to http://virt.kernelnewbies.org/TechComparison.

Qemu can emulate a host machine in software, or given a CPU with hardware support (see below) can use KVM to provide a fast full virtualization.

Other virtualization products and packages are available but are not covered by this guide.

Installing and configuring Fedora For virtualized guests

This section covers setting up libvirt on your system. After the successful completion of this section you will be able to create virtualized guest operating systems.

System requirements

The common system requirements for virtualization on Fedora are:

• At least 600MB of hard disk storage per guest. A minimal command-line fedora system requires 600MB of storage. Standard fedora desktop guests require at least 3GB of space.
• At least 256MB of RAM per guest plus 256 for the base OS. At least 756MB is recommended for each guest of a modern operating system. A good rule of thumb is to think about how much memory is required for the operating system normally and allocate that much to the virtualized guest.

KVM requires a CPU with virtualization extensions, found on most consumer CPUs made in the past couple years. These extensions are called Intel VT or AMD-V. To check whether you have proper CPU support, run the command:

$ egrep '^flags.*(vmx|svm)' /proc/cpuinfo 

If NOTHING is printed, your system does not support the relevant extensions. You can still use the QEMU/KVM, but the emulator will fall back to software virtualization, which is FAR FAR slower.

Installing the virtualization packages

When installing Fedora, the virtualization packages can be installed by selecting Virtualization in the Base Group in the installer.

For existing Fedora installations, QEMU, KVM, and other virtualization tools can be installed by running the following command which installs the virtualization group:

su -c "yum install @virtualization"

This will install qemu-kvm, python-virtinst, qemu, virt-manager, virt-viewer and all dependencies are needed.

By default, the libvirtd service will be started on host boot up, but it needs to be started manually after installing the above group:

su -c "service libvirtd start"

Or in newer version of Fedora which use systemd:

su -c "systemd-systemctl start libvirtd"

Verify that the kvm kernel modules were properly loaded:

$ lsmod | grep kvm
kvm_amd                55563  0 
kvm                   419458  1 kvm_amd

If that command did not list kvm_intel or kvm_amd, KVM is not properly configured. See Ensuring system is KVM capable for troubleshooting tips.

Networking Support

By default libvirt will create a private network for your guests on the host machine. This private network will use a 192.168.x.x subnet and not be reachable directly from the network the host machine is on, but virtual guests can use the host machine as a gateway and can connect out via it. If you need to provide services on your guests that are reachable via other machines on your host network you can use iptables DNAT rules to forward in specific ports, or you can setup a Bridged env.

See the libvirt networking setup page for more information on how to setup a Bridged network.

Creating a Fedora guest

The installation of Fedora guests using anaconda is supported. The installation can be started on the command line via the virt-install program or in the GUI program virt-manager.

Creating a guest with virt-install

virt-install is a command line based tool for creating virtualized guests. To start the interactive install process, run the virt-install command with the --prompt parameter.

su -c "/usr/bin/virt-install --prompt"

The following questions for the new guest will be presented.

1. What is the name of your virtual machine? This is the label that will identify the guest OS. This label is used with virsh commands and virt-manager(Virtual Machine Manager).
2. How much RAM should be allocated (in megabytes)? This is the amount of RAM to be allocated for the guest instance in megabytes (eg, 256). Note that installation with less than 256 megabytes is not recommended.
3. What would you like to use as the disk (path)? The local path and file name of the file to serve as the disk image for the guest (eg, /var/lib/libvirt/images/name.img). This will be exported as a full disk to your guest. It's best to specify the default /var/lib/libvirt/images/ directory.
4. How large would you like the disk to be (in gigabytes)? The size of the virtual disk for the guest (only appears if the file specified above does not already exist). 4.0 gigabytes is a reasonable size for a "default" install
5. What is the install CD-ROM/ISO or URL? This is the path to a Fedora installation tree in the format used by anaconda. NFS, FTP, and HTTP locations are all supported. Examples include:
   • nfs:my.nfs.server.com:/path/to/test2/tree/
   • http://my.http.server.com/path/to/tree/
   • ftp://my.ftp.server.com/path/to/tree

These options can be passed as command line options, execute virt-install --help for details.

virt-install can use kickstart files, for example virt-install -x ks=kickstart-file-name.ks.

If graphics were enabled, a VNC window will open and present the graphical installer. If graphics were not enabled, a text installer will appear. Proceed with the fedora installation.

Creating a guest with virt-manager

Start the GUI Virtual Machine Manager by selecting it from the "Applications-->System Tools" menu, or by running the following command:

su -c "virt-manager"

If you encounter an error along the lines of "Failed to contact configuration server; some possible causes are that you need to enable TCP/IP networking for ORBit, or you have stale NFS locks due to a system crash", trying running virt-manager not as root (without the su -c). The GUI will prompt for the root password.

1. Open a connection to a hypervisor by choosing File-->Add connection...
2. Choose "qemu" for KVM, or "Xen" for Xen.
3. Choose "local" or select a method to connect to a remote hypervisor
4. After a connection is opened, click the new icon next to the hypervisor, or right click on the active hypervisor and select "New" (Note - the new icon is going to be improved to make it easier to see)
5. A wizard will present the same questions as appear with the virt-install command-line utility (see descriptions above). The wizard assumes that a graphical installation is desired and does not prompt for this option.
6. On the last page of the wizard there is a "Finish" button. When this is clicked, the guest OS is provisioned. After a few moments a VNC window should appear. Proceed with the installation as normal.

Remote management

The following remote management options are available:

• (easiest) If using non-root users via SSH, then setup instructions are at: http://wiki.libvirt.org/page/SSHSetup
• If using root for access via SSH, then create SSH keys for root, and use ssh-agent and ssh-add before launching virt-manager.
• To use TLS, set up a local certificate authority and issue x509 certs to all servers and clients. For information on configuring this option, refer to http://wiki.libvirt.org/page/TLSSetup.

Guest system administration

When the installation of the guest operating system is complete, it can be managed using the GUI virt-manager program or on the command line using virsh.

Managing guests with virt-manager

Start the Virtual Machine Manager. Virtual Machine Manager is in the "Applications-->System Tools" menu, or execute:

su -c "virt-manager"

{1} If you are not root, you will be prompted to enter the root password. ChooseRun unprivileged to operate in a read-only non-root mode.

• Choose the host you wish to manage and click "Connect" in the "Open Connection" dialog window.
• The list of virtual machines is displayed in the main window. Guests that are running will display a ">" icon. Guests that are not running will be greyed out.
• To manage a particular guest, double click on it, or right click and select "Open".
• A new window for the guest will open that will allow you to use its console, see information about its virtual hardware and start/stop/pause it.

For further information about virt-manager consult the project website

Bugs in the virt-manager tool should be reported in BugZilla against the 'virt-manager' component

Managing guests with virsh

The virsh command line utility that allows you to manage virtual machines. Guests can be managed on the command line with the virsh utility. The virsh utility is built around the libvirt management APIl:

• virsh has a stable set of commands whose syntax and semantics are preserved across updates to the underlying virtualization platform.
• virsh can be used as an unprivileged user for read-only operations (e.g. listing domains, listing domain statistics).
• virsh can manage domains running under Xen, Qemu/KVM, esx or other backends with no perceptible difference to the user

A valid URI may be passed to virsh with "-c' to connect to a remote libvirtd instance. For details, see http://libvirt.org/uri.html

To start a virtual machine:

su -c "virsh create <name of virtual machine>"

To list the virtual machines currently running:

su -c "virsh list"

To list all virtual machines, running or not:

su -c "virsh list --all"

To gracefully power off a guest:

su -c "virsh shutdown <virtual machine (name | id | uuid)>"

To non gracefully power off a guest:

su -c "virsh destroy <virtual machine (name | id | uuid)>"

To save a snapshot of the machine to a file:

su -c "virsh save <virtual machine (name | id | uuid)> <filename>"

To restore a previously saved snapshot:

su -c "virsh restore <filename>"

To export the configuration file of a virtual machine:

su -c "virsh dumpxml <virtual machine (name | id | uuid)"

For a complete list of commands available for use with virsh:

su -c "virsh help"

Or consult the manual page: man 1 virsh

Bugs in the virsh tool should be reported in BugZilla against the 'libvirt' component.

Other virtualization options

QEMU/KVM without Libvirt

QEMU/KVM can be invoked directly without libvirt, however you won't be able to use tools such as virt-manager, virt-install, or virsh. Plain QEMU (without KVM) can also virtualize other processor architectures like ARM or PowerPC. See How to use qemu

Xen

Fedora can run as a Xen Guest OS, but using Fedora as a Xen Host is currently not supported. There is an experimental repo available at http://myoung.fedorapeople.org/dom0

OpenStack

OpenStack consists of a number services for running IaaS clouds. They are the Object Store (Swift), Compute (Nova) and Image (Glance) services. It is a Fedora 16 feature.

OpenNebula

OpenNebula is an Open Source Toolkit for Data Center Virtualization.

oVirt

The oVirt project is an open virtualization project providing a feature-rich, end to end, server virtualization management system with advanced capabilities for hosts and guests, including high availability, live migration, storage management, system scheduler, and more.

Troubleshooting, bug reporting, and known issues

For a list of known unresolved issues, as well as troubleshooting tips, please see How to debug virtualization problems