我现在只能进到图形界面里，然后在右上角的“Manual network configuration”里设置打开或禁用无线网。
我以前都是用“sudo ifup/ifdown eth0”来打开或关闭我的有线网。但是现在我用“sudo ifup ath0”却被提示“Ignoring unknown interface ath0=ath0.”，我在/etc/network/interfaces文件里面，也没有看到ath0的配置。
我在论坛里也没搜到能解答我的文章，所以想在此问一下，怎么在命令行里做以下事情：
1. 开启或禁用无线网卡
2. 当附近有多个无线网络时，我怎么选择连接到哪一个。
谢谢。
以下是我的网卡的一些信息。
代码： 全选
ath0 Link encap:Ethernet HWaddr 00:17:C4:00:9B:AE
inet6 addr: fe80::217:c4ff:fe00:9bae/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:20 errors:0 dropped:0 overruns:0 frame:0
TX packets:80 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:4338 (4.2 KiB) TX bytes:12486 (12.1 KiB)
eth0 Link encap:Ethernet HWaddr 00:16:36:91:BB:6F
inet addr:192.168.0.26 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::216:36ff:fe91:bb6f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2387 errors:0 dropped:0 overruns:0 frame:0
TX packets:2690 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2052761 (1.9 MiB) TX bytes:483837 (472.4 KiB)
Interrupt:19 Base address:0x6000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:2 errors:0 dropped:0 overruns:0 frame:0
TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:100 (100.0 b) TX bytes:100 (100.0 b)
wifi0 Link encap:UNSPEC HWaddr 00-17-C4-00-9B-AE-00-00-00-00-00-00-00-00-00-00
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1542 errors:0 dropped:0 overruns:0 frame:253
TX packets:300 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:199
RX bytes:108103 (105.5 KiB) TX bytes:24307 (23.7 KiB)
Interrupt:16 