8 VBoxManage • --natdnsproxy1-N on|off: This option makes the NAT engine proxy all guest DNS requests to the host’s DNS servers (please see chapter 9.10.5, Enabling DNS proxy in NAT mode, page 147 for details). • --natdnshostresolver1-N on|off: This option makes the NAT engine use the host’s resolver mechanisms to handle DNS requests (please see chapter 9.10.5, Enabling DNS proxy in NAT mode, page 147 for details). • --natnatsettings1-N [mtu],[socksnd],[sockrcv],[tcpsnd], [tcprcv]: This option controls several NAT settings (please see chapter 9.10.3, Tuning TCP/IP buffers for NAT, page 146 for details). • --nataliasmode1-N default|[log],[proxyonly],[sameports]: This option de- fines behaviour of NAT engine core: log - enables logging, proxyonly - switches of aliasing mode makes NAT transparent, sameports enforces NAT engine to send packets via the same port as they originated on, default - disable all mentioned modes above . (please see chap- ter 9.10.7, Configuring aliasing of the NAT engine, page 147 for details). 8.7.3 Serial port, audio, clipboard, remote desktop and USB settings The following other hardware settings are available through VBoxManage modifyvm: • --uart1-N off|I/O base IRQ: With this option you can configure virtual serial ports for the VM see chapter 3.9, Serial ports, page 48 for an introduction. • --uartmode1-N arg: This setting controls how VirtualBox connects a given virtual serial port (previously configured with the --uartX setting, see above) to the host on which the virtual machine is running. As described in detail in chapter 3.9, Serial ports, page 48, for each such port, you can specify arg as one of the following options: – disconnected: Even though the serial port is shown to the guest, it has no “other end” – like a real COM port without a cable. – server pipename: On a Windows host, this tells VirtualBox to create a named pipe on the host named pipename and connect the virtual serial device to it. Note that Windows requires that the name of a named pipe begin with \\.\pipe\. On a Linux host, instead of a named pipe, a local domain socket is used. – client pipename: This operates just like server ..., except that the pipe (or local domain socket) is not created by VirtualBox, but assumed to exist already. – devicename: If, instead of the above, the device name of a physical hardware serial port of the host is specified, the virtual serial port is connected to that hardware port. On a Windows host, the device name will be a COM port such as COM1 on a Linux host, the device name will look like /dev/ttyS0. This allows you to “wire” a real serial port to a virtual machine. • --audio none|null|oss: With this option, you can set whether the VM should have audio support. • --clipboard disabled|hosttoguest|guesttohost|bidirectional: With this set- ting, you can select whether the guest operating system’s clipboard should be shared with the host see chapter 3.3, General settings, page 42. This requires that the Guest Additions be installed in the virtual machine. • --monitorcount count: This enables multi-monitor support see chapter 3.5, Display settings, page 45. • --usb on|off: This option enables or disables the VM’s virtual USB controller see chapter 3.10.1, USB settings, page 49 for details. 113