FAQ
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From IRC
- Does oVirt have support for managing Xen?
Managing existing RHEL/Xen instances is on the roadmap but not yet complete.
- Does oVirt have support for OpenVZ?
oVirt uses libvirt which supports OpenVZ, but OpenVZ is not the main focus. Our efforts at the present time primarily focus on KVM. Additional platforms and hypervisors will be supported by oVirt as the project matures or as we get community support for them.
- oVirt is supposed to be based on libvirt, and libvirt supports Hypervisor X, so why doesn't oVirt support that hypervisor?
libvirt provides the underlying framework for managing hypervisors and guests, but oVirt is more than just a layer on top of libvirt. oVirt also provides mechanisms for host/guest performance data collection (through collectd), state notification and integration with FreeIPA for security management. So while libvirt makes it easy to support additional hypervisors, each new platform will require some work to port over the oVirt specific code and scripts.
- I'm interested in helping to get hypervisor X supported in oVirt, where do I start?
The best place to start is by taking a look at the oVirt Managed Node. Most of the oVirt specific code for the Managed Node is contained in the ovirt-managed-node RPM which is in the source repository. In addition, the UI and Taskomatic (the daemon which processes host/guest related tasks) needs to be updated to support multiple hypervisors.
- How can oVirt be made highly available?
The appliance that is available for download provides all of the oVirt services contained in a single guest image. The appliance is provided for consumption by two audiences: people looking to try out oVirt and see what its capabilities are and small environments where there is no existing infrastructure to integrate with. For most other environments oVirt will need to be installed and integrated with other components. We are currently working on an installation script and documentation for this installation method. In this install method, components like the underlying database, the web user interface, Taskomatic and other daemons can be installed on separate hardware. Normal clustering and HA techniques can be used to ensure that the oVirt infrastructure pieces are highly available.
- Can guests running on oVirt be used with a distributed file system?
oVirt is generally agnostic to the underlying filesystems used by guests. There is presently one restriction in the user interface code that prevents this, however. At the present time each guest must be assigned a unique iSCSI LUN or NFS target. This means that guests cannot share filesystems. Work is in progress to enhance our storage interfaces, but we would be happy to accept patches to help move this along.
- I have a question about how libvirt works or is used.
oVirt developers are generally knowledgeable about libvirt and we'll try to answer any questions that we can on the IRC channel. If we're not around or if we don't have the answer to a specific question, please check out the libvirt contact page.
- oVirt is awesome, how do I help?
Take a look at our contributions page.
Basic questions
- What license is oVirt distributed under?
The oVirt web management application is distributed under the GNU General Public License v2, see the file COPYING in the distribution for the precise wording. The pre-built host and appliance images are built on top of a Fedora distribution, whose components are covered by a variety of open source licenses.
- What language is the application written in?
The application is being written in Ruby, using Rails because it allows for fast and flexible development.
- How do I get oVirt?
Download our prebuilt image from the download page, or download the kickstart from that page and build the image yourself (this might be faster if you have a local Fedora mirror for example). See the installation instructions for details.
- How do I contribute to oVirt?
Patches are enthusiastically accepted at oVirt-devel@redhat.com. Keep in mind that oVirt is developing rapidly; it's probably better to ask on the list before spending a lot of time on a feature someone else is working on. Also say hello to developers on the #ovirt channel on irc.freenode.net
- What underlying virtualization technology does oVirt use?
Because we use libvirt for all our VM management and communication, we are not tied to a particular hypervisor implementation or technology. For optimal hardware support our pre-built images use the KVM technology built into main Linux kernel.
- Who should use oVirt?
Anyone who wants to manage virtual machines! We intend oVirt to be lightweight enough to work for a developer managing, say, a single host with four VMs, yet robust enough for a large organization managing tens of thousands of VMs. Also, although we develop using Fedora, we aggressively avoid being tied to a particular platform. Solaris and Windows users should be able to use the oVirt browser interface, and in the future we want the oVirt management console to run across platforms as well.
Deployment
- What are the LAN services required for deployment?
oVirt requires that a handful of network services be available on the local LAN:
- DNS
- required to be able to add persistent DNS names for the oVirt management application, and Kerberos servers
- DHCP
- required to configure a PXE image for booting oVirt managed host nodes, and set local configuration options such as Kerberos/iSCSI server names.
- TFTP
- required to serve the PXE image for booting oVirt managed host nodes. The Cobbler application provides an easy way to manage DHCP and TFTP services
- iSCSI
- guest virtual machines use iSCSI volumes for their storage, one iSCSI LUN per guest disk. This restriction will be relaxed in the future to allow use of LVM and direct attached fiber channel storage. The OpenFiler appliance provides a convenient pre-built OS for serving iSCSI targets
- Kerberos
- the oVirt management web UI and libvirt services authenticate using Kerberos principles. The FreeIPA project provides an incredibly easy way to deploy Kerberos servers based on Fedora.
- What are the minimal physical hardware requirements?
For the purposes of development, the minimum hardware requirements is a single machine capable of of running KVM guests (see the developer installation instructions for more details).
- What are the recommended hardware requirements?
Once the application matures to a level where it is suitable for use in production, the recommended minimum hardware for production deployments will be:
- Host providing Kerberos/LDAP
- Host (or filer) providing iSCSI
- Host providing oVirt management web UI
- Host providing services for DHCP/DNS/TFTP
- Multiple oVirt managed hosts for running guests
- 2 network interfaces in each machine, one dedicated for iSCSI data
- I don't have a Kerberos/LDAP server, how do I provide authentication services?
FreeIPA project is integrating Kerberos, Fedora Directory Server, and a handful of related applications into one easy-to-deploy package. If you use the oVirt developer or bundled install, FreeIPA is built right into the appliance. If you want to try FreeIPA on your own, packages are available for both Fedora 8 and Fedora 9 in the default repositories.
- I don't have an iSCSI servers, how do I provide storage?
The OpenFiler project provides a prebuilt OS image which is able to export a machine's disks / LVM volumes as iSCSI LUNs (and other storage / filesystem protocols). This provides a very easy and cheap alternative to a Netapp filer. Alternatively the *scsi-target-utils* application in Fedora can be used to serve iSCSI LUNs from an existing machine with spare storage capacity; see the iSCSI setup instructions for more details.
- I don't have a DHCP/TFTP server, how do I provide PXE boot support?
If you are using the oVirt developer or bundled install, PXE support is built right into the appliance. If you want to setup PXE on your own, the Cobbler project provides a very powerful application for automating the management of DHCP and TFTP services suitable for PXE boot installation of both hosts and guests. It is part of Fedora and available for most other Linux distributions.
Administration
- Can I directly connect to managed hosts, bypassing the web UI?
All communication between the oVirt web UI and the managed hosts takes place using libvirt APIs. So any libvirt enabled application can also connect to the managed hosts. For example the virsh command can be used to manage VMs, though it is recommended that all management by done via the web UI unless major problems have occurred requiring manual recovery.
- How can I access the graphical console for guests?
The virt-viewer application can be used to access guest graphical consoles. It is required that the client host be kerberos enabled and that the user running virt-viewer have a valid kerberos ticket.
Troubleshooting
- What does this libvirt error message mean?
libvir: Remote error : Failed to start SASL negotiation: -4 (SASL(-4): no mechanism available : No worthy mechs found
This indicates that the libvirt client was unable to start the Kerberos negotiation. This is usually because the cyrus-sasl-gssapi RPM is missing.
- Why is the oVirt management interface extremely slow?
This generally happens because you are using regular Qemu CPU emulation instead of KVM virtualization. Make sure to check that the module "kvm_intel" or "kvm_amd" is loaded on your host machine (note that just the "kvm" module is *not* sufficient).
If the appropriate KVM modules are not loaded, make sure that your processor supports virtualization and that virtualization is turned on in the BIOS. If it came disabled in the BIOS, and you changed the BIOS setting to turn virtualization on, you also have to physically power down the host machine. Just rebooting the machine frequently does *not* work.
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