On 12.04, running as a guest in VirtualBox using two adapters, I was getting this error in response to
RTNETLINK answers: File exists Failed to bring up eth1
This was the contents of
# The loopback network interface auto lo iface lo inet loopback # Host-only interface auto eth1 iface eth1 inet static address 192.168.56.20 netmask 255.255.255.0 network 192.168.56.0 broadcast 192.168.56.255 gateway 192.168.56.1 # NAT interface auto eth2 iface eth2 inet dhcp
See this question for more about why I configured it this way.
In VirtualBox, how do I set up host-only virtual machines that can access the Internet?