运行ovs后，Linux系统中会多出一块状态是down掉的网卡ovs-system：
ifconfig -a
...
ovs-system Link encap:Ethernet HWaddr FA:4F:0D:E4:DA:11
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:468 (468.0 b)
...
历史原因，Open vSwitch在内核中使用的是datapath，而每个datapath必须有一个端口与之对应，ovs使用的datapath名字是ovs-system，所以系统中就冒出来一个ovs-system的网卡，没有任何用途，忽略它既可。你也根本删不掉它的。
It's not used for anything, and not useful for anything. It is mostly historical. A Linux kernel Open vSwitch datapath needs to have a port named the same as the datapath. Open vSwitch needs one datapath, and it
names it ovs-system, so there's a port with the same name, even though it doesn't get used for anything.