Features

General

• Pluggable backends including
  • xc: drives Xen via libxc and libxenguest
  • xenlight: drives Xen via libxenlight and libxc
  • libvirt: drives Xen via libvirt
  • qemu: drives KVM by running qemu processes
  • simulator: simulates operations for component-testing
• Supports running multiple instances and backends on the same host, looking after different sets of VMs
• Distribution agnostic, known to work on
  • XenServer
  • CentOS 6.*
  • Ubuntu 14.04
  • Fedora 21
• Extensive configuration via command-line (see manpage) and config file
• Command-line tool for easy VM administration and troubleshooting
• User-settable degree of concurrency to get VMs started quickly

VMs

• VM start/shutdown/reboot
• VM suspend/resume/checkpoint/migrate
• VM pause/unpause
• VM s3suspend/s3resume
• customisable SMBIOS tables for OEM-locked VMs
• hooks for 3rd party extensions:
  • pre-start
  • pre-destroy
  • post-destroy
  • pre-reboot
• per-VM xenguest replacement
• suppression of VM reboot loops
• live vCPU hotplug and unplug
• vCPU to pCPU affinity setting
• vCPU QoS settings (weight and cap for the Xen credit2 scheduler)
• DMC memory-ballooning support
• support for storage driver domains
• live update of VM shadow memory
• guest-initiated disk/nic hotunplug
• guest-initiated disk eject
• force disk/nic unplug
• support for ‘surprise-removable’ devices
• disk QoS configuration
• nic QoS configuration
• persistent RTC
• two-way guest agent communication for monitoring and control
• network carrier configuration
• port-locking for nics
• text and VNC consoles over TCP and Unix domain sockets
• PV kernel and ramdisk whitelisting
• configurable VM videoram
• programmable action-after-crash behaviour including: shutting down the VM, taking a crash dump or leaving the domain paused for inspection
• ability to move nics between bridges/switches
• advertises the VM memory footprints
• PCI passthrough
• support for discrete emulators (e.g. ‘demu’)
• PV keyboard and mouse
• qemu stub domains
• cirrus and stdvga graphics cards
• HVM serial console (useful for debugging)
• support for vGPU
• workaround for ‘spurious page faults’ kernel bug
• workaround for ‘machine address size’ kernel bug

Hosts

• CPUid masking for heterogenous pools: reports true features and current features
• Host console reading
• Hypervisor version and capabilities reporting
• Host CPU querying

APIs

• versioned json-rpc API with feature advertisements
• clients can disconnect, reconnect and easily resync with the latest VM state without losing updates
• all operations have task control including
  • asychronous cancellation: for both subprocesses and xenstore watches
  • progress updates
  • subtasks
  • per-task debug logs
• asynchronous event watching API
• advertises VM metrics
  • memory usage
  • balloon driver co-operativeness
  • shadow memory usage
  • domain ids
• channel passing (via sendmsg(2)) for efficent memory image copying