eth0 missing and ip is always 10.0.2.15 issues in ubuntu under VirtualBox

Solution for eth0 missing issue:
1. rm /etc/udev/rules.d/70-persistent-net.rules, and shutdown.
2. In VirtualBox settings->Network, refresh the MAC.
3. start ubuntu and the eth0 appears.

Solution for ip=10.0.2.15 issue(use "dhclient" to refetch ip from dhcp server):
1. Configure to fetch IP via dhcp: /etc/network/interfaces
auto lo eth0
iface lo inet loopback
iface eth0 inet dhcp

2. In VirtualBox settings->network->"Attached to", change from "NAT" to "Bridged Adapter".



然后设置浏览器的代理和apt-get的代理即可以工作。
ubuntu@ubuntu-VirtualBox:/etc/apt$ cat apt.conf
Acquire::http::Proxy "http://www-proxy.ericsson.se:8080";