#Pythonpune

Libvirt API

Amol Kahat

What is Libvert?

• Libvirt is a hypervisor-independent virtualization API and toolkit that is able to interact with the virtualization capabilities of a range of operating systems.
• It is free software under the GNU Lesser General Public License.
• It provides a common, generic and stable layer to securely manage domains on a node.
• it does not provide high level virtualization policies or multi- node management features such as load balancing.

Goals of Libvert API

• Virtualization library: manage guest on one node
• Share the application stack between hypervisors
• Long term stability and compatibility of API
• Provide security and remote access
• Expand to management APIs (Node, Storage, Network)

Terms

• Domain : An instance of an operating system running on a virtualized machine provided by the hypervisor.
• Hypervisor : A layer of software allowing virtualization of a node in a set of virtual machines, which may have different configurations to the node itself.
• Node : A single physical server. Nodes may be any one of many different types, and are commonly referred to by their primary purpose.
• Storage Pool : A collection of storage media, such as physical hard drives. A Storage Pool is sub-divided into smaller containers called Volumes, which may then be allocated to one or more Domains.
• Volume : A storage space, allocated from a Storage Pool. A Volume may be assigned to one or more Domains for use, and are commonly used inside Domains as virtual hard drives.

Architecture

Connections

• Open / Close Connection
  1. conn = libvirt.open(name)
  2. conn = libvirt.openAuth(uri, auth, flags)
  3. conn = libvirt.openReadOnly(name)
  4. conn.close()
• URI Formats
  1. Local URI
  Syntax :
  1. dirver://system
  2. dirver://session

2. Remote URI
1. driver[+transport]://[username@][hostname][:port][/path][?exactPrarams]

• Capability Information
  1. caps = conn.getCapabilities()
• Host Information
  • getHostname()
  • getMaxVcpus()
  • getInfo()
  • getCellsFreeMemory()
  • getVersion()
  • getLibVersion()

Guest Domains

• Domains
• Transient
• Persistent
• Lifecycle Control

Domain Configuration

• Domains are defined in libvert using XML.
• Everything related only to the domain, such as memory and CPU, is defined in the domain XML.
• 1. Boot Modes
  2. Memory / CPU Resources

Virtual Networks

• A virtual network provides a method for connecting the network devices of one or more guest domains within a single host. The virtual network can either:
  1. Remain isolated to the host; or
  2. Allow routing of traffic off-node via the active network interfaces of the host OS. This includes the option to apply NAT to IPv4 traffic.
• A virtual network may be transient or persistent.
• Examples:
  • conn.networkLookupByName()
  • conn.networkLookupByUUID()
  • conn.networkLookupByUUIDString()

Any Questions?

Thank You