The easiest way to use virtual networking is to use the "daemon"
transport with the uml_switch instance which is configured and running
by default.

1. Add an entry to /etc/network/interfaces to configure a persistent
tap interface on the host:

auto tap0
iface tap0 inet static
        address 192.168.1.1
        netmask 255.255.255.0
        tunctl_user uml-net

2. Configure uml_switch to connect to this interface by editing
/etc/default/uml-utilities:

UML_SWITCH_OPTIONS="-tap tap0"

3. Activate the tap interface:

# ifup tap0

4. Restart the daemon

# /etc/init.d/uml-utilities restart

5. Use the "daemon" transport with UML:

$ linux eth0=daemon

You should then be able to pass traffic between UML and the host over
the tap interface.  You may also set up forwarding, masquerading,
etc. in order to communicate beyond the host.  It is convenient to run
dhcpd on the host, configured to listen on the tap0 interface and
provide configuration information for UMLs as needed.

As an alternative to the above procedure, to enable virtual networking
using TUN/TAP directly from UML (the "tuntap" transport), add trusted
users to the uml-net group, e.g.:

adduser bill uml-net

If you wish to use a different group or different permissions, use a
statoverride for /usr/lib/uml/uml_net.  Note that members of the
uml-net group will have privileges to do potentially harmful things to
the system, such as reconfiguring network interfaces.

Note also that the uml_net helper is installed in a different place in this
package than by the upstream distribution (/usr/lib/uml/uml_net rather than
PREFIX/bin/uml_net).  This is done in order to comply with FHS.  because
uml_net is not meant to be executed by users, it does not belong in the system
PATH.

 -- Matt Zimmerman <mdz@debian.org>, Sun Sep 28 23:08:26 2003