是不是试了很多方法之后还是不行？:）

我的虚拟机网络设置为桥接模式，输入ifconfig只显示127.0.0.1，不能连上外网。

xxx@ubuntu:~$ ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (本地环回)
        RX packets 4749  bytes 287841 (287.8 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 4749  bytes 287841 (287.8 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

1、sudo -i切换为root用户

2、输入dhclient -v

再输入ifconfig就可以看到多了一个ip地址

root@ubuntu:~# ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.203.2.196  netmask 255.255.255.224  broadcast 10.203.2.223
        inet6 2001:da8:215:c316:20c:29ff:fe3b:830b  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::20c:29ff:fe3b:830b  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:3b:83:0b  txqueuelen 1000  (以太网)
        RX packets 8  bytes 1251 (1.2 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 54  bytes 8642 (8.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (本地环回)
        RX packets 4942  bytes 299699 (299.6 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 4942  bytes 299699 (299.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

这样就可以正常上网啦，记得输入exit回到登录者用户哦

有的同学说重启后命令失效，请参考下面的方法：
1、执行vim ~/.bashrc
2、在最后一行添加dhclient -v
3、保存退出
4、执行source ~/.bashrc使其立即生效