从VirualBox 4.2 Beta1 到 VirualBox 4.2 RC4，这时VirualBox最长的一次版本进化，伴随着N多改进，这包括对OS X ML和Win8适配，网络带宽控制，虚拟机分组，剪贴板共享和Drag'n'drop拖拽等期待已久的功能，尤其是Drag'n'drop拖拽，该功能早在六年前[]，社区就有人提出了，但一直没能实现，其实核心代码早已支持（vbox 是 based on QEMU的），只是Addition需要做些处理。另外，这个版本界面也变得更加美观和实用了。Good Job !

Changelog:

VirtualBox 4.2.0 (released 2012-09-13)

This version is a major update. The following major new features were added:

• Improved Windows 8 support, in particular many 3D-related fixes
• GUI: VM groups (bug )
• GUI: expert mode for wizards
• GUI: allow to alter some settings during runtime
• Support for up to 36 network cards, in combination with an ICH9 chipset configuration (bug )
• Resource control: added support for limiting network IO bandwidth; see the manual for more information (bug )
• Added possibility to start VMs during system boot on Linux, OS X and Solaris; see the manual for more information (bug )
• Added experimental support for Drag'n'drop from the host to Linux guests. Support for more guests and for guest-to-host is planned. (bug )
• Added support for parallel port passthrough on Windows hosts
• Enhanced API for controlling the guest; please see the SDK reference and API documentation for more information

In addition, the following items were fixed and/or added:

• • Mac OS X hosts: sign application and installer to avoid warnings on Mountain Lion
  • VMM: fixed a potential host crash triggered by shutting down a VM when another VM was running (only affected 32-bit hosts and 64-bit OS X hosts, 4.1 regression, bug )
  • VMM: fixed a potential host crash under a high guest memory pressure (seen with Windows 8 guests)
  • VMM: improved VM context switch performance for Intel CPUs using nested paging
  • VMM: added support for FlushByASID features of AMD CPUs (Bulldozer and newer)
  • VMM: fixed unreal mode handling on older CPUs with VT-x (gPXE, Solaris 7/8/9; bug )
  • VMM: fixed MP tables fixes for I/O APIC interrupt routing relevant for ancient SMP guests (e.g. old OS/2 releases)
  • VMM: support recent VIA CPUs (bug )
  • VMM: fixed handling of task gates if VT-x/AMD-V is disabled
  • VMM: page fusion fixes
  • GUI: network operations manager
  • GUI: allow taking screenshots of the current VM window content (bug )
  • GUI: allow automatically sorting of the VM list
  • GUI: allow starting of headless VMs from the GUI
  • GUI: allow reset, shutdown and power off from the Manager window
  • GUI: allow to globally limit the maximum screen resolution for guests
  • GUI: show the full medium part on hovering the list of recently used ISO images
  • GUI: do not create additional folders when a new machine has a separator character in its name (bug )
  • GUI: don't crash on terminate if the settings dialog is still open (bug )
  • GUI: consider scaled DPI values when display fonts on Windows hosts (bug )
  • GUI: if a bridged network interface cannot be found, don't refuse to start the VM but allow the user to change the setting immediately
  • Snapshots: fixed a crash when restoring an old snapshot when powering off a VM (bugs , , )
  • Clipboard: disable the clipboard by default for new VMs (see the manual for more information). It can be enabled at any time using the VM menu.
  • Settings: sanitize the name of VM folders and settings file (bug )
  • Settings: allow to store the iSCSI initiator secret encrypted
  • NAT: improvements for the built-in TFTP server (bugs , )
  • NAT: fixed memory leak when disabling the NAT engine (bug )
  • E1000: 802.1q VLAN support (bug )
  • Storage: implemented burning of audio CDs in passthrough mode
  • Storage: fixed audio CD passthrough for certain media players
  • Storage: implemented support for discarding unused image blocks through TRIM for SATA and IDE and UNMAP for SCSI when using VDI images
  • Storage: added support for QED images
  • Storage: added support for QCOW (full support for v1 and readonly support for v2 images)
  • Storage: added readonly support for VHDX images
  • USB: don't crash if a USB device is plugged or unplugged when saving or loading the VM state (SMP guests only)
  • Solaris additions: added support for X.org Server 1.11 and 1.12
  • Solaris additions: switched to using an in-kernel mouse driver
  • Windows hosts: no need to recreate host-only adapters after a VirtualBox update
  • Windows hosts: updated toolchain; make the source code compatible to VC 2010 and enable some security-related compiler options
  • Windows Additions: fixed memory leak in VBoxTray (bug )