Device support

All devices seen by the user-mode kernel are virtual from the point of view of the host. They are constructed from software abstractions provided by the host. The following types of devices are provided:

Consoles

The main console is whatever terminal the kernel was invoked in. In addition, virtual consoles are supported. By default, they execute an xterm when opened. Optionally, they can just allocate a pseudo-terminal which the user can connect to with a terminal program such as minicom or kermit.

Block devices

The block device driver operates within a file on the host. Normally, this is a file containing a filesystem or swap space. However, any file on the host that is seekable is suitable. Among other things, this means that devices on the host can be accessed through their device files.

Serial lines

The serial line driver allocates a pseudo-terminal. Users wanting to connect to the virtual machine via a serial line can do so by connecting to the appropriate pseudo-terminal with a terminal program.

Network devices

There are two network device drivers. The old network driver communicates with the host networking system through a slip device in the host. The virtual machine's side of the connection is a pseudo-terminal in the host which appears as a network device inside. There is also a newer network driver which uses an external daemon to pass Ethernet frames between virtual machines. This daemon can also attach this virtual network to the host's physical Ethernet by way of an ethertap device. With an appropriate packet forwarding policy in the daemon, the virtual Ethernet can be transparently merged with the physical Ethernet, totally isolated from it, or anything in between.