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Thread: Ubuntu Server - USB Wireless CLI config

  1. #1
    Join Date
    Mar 2009

    Ubuntu Server - USB Wireless CLI config


    I've decided to setup a PC with Ubuntu server so it can serve me as a FTP server and perhaps even more in the future.

    Soon after install I knew I will have to face the command line interface but what I didn't expect was that my Ethernet Controller somehow died and the computer wont boot with the Ethernet controller in it.

    The original plan was to download the ubuntu-desktop and install it using the wired connection with the Ethernet Controller. After I would complete that I would install the USB Wireless network card and configure it in GUI to work properly. The problem now is that the USB wi-fi card now can't be configuered since I have absolutely NO knowledge of using the CLI. (Been suffering Windows for quite a long time).

    Then I gave it some thought and came up with "Hey maybe this is a great opportunity for me to learn how to use the CLI". I am also running Ubuntu Desktop distro on my laptop and knowing the CLI would help advance in Linux usage.

    So why did I start this thread...

    First of all I want to get my USB Wi-fi card running so I get connection and then step it up to server configuration. I will put all my future questions, problems etc. in this thread.

    Problem no.1 : How to get the USB Wi-fi configured using only CLI? (USB wireless network card - TP-Link TL-WN422G)

    Thank you in advance.

  2. #2
    Join Date
    Nov 2007

    Re: Ubuntu Server - USB Wireless CLI config

    Let's assume your USB device is properly recognized and configured.
    TIP - Each of the commands below has a man page installed on your system. Try '$man iwconfig', for example.

    1) The 'iwconfig' command will tell you what wireless interfaces you have available, including wired, wireless, loopback, and other.

    Let's say your new wireless interface is on 'eth1'. Yours may well have a different name - just change the name in the next steps.

    $ iwconfig
    lo        no wireless extensions.
    eth0      no wireless extensions.
    wmaster0  no wireless extensions.
    eth1      IEEE 802.11g  ESSID:""  Nickname:""
              Mode:Managed  Frequency:  Access Point:   
              Bit Rate=   Tx-Power=
              Retry min limit:   RTS thr:   Fragment thr=   
              Power Management:off
              Link Quality=     Signal level=    Noise level= 
              Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
              Tx excessive retries:0  Invalid misc:0   Missed beacon:0
    2) The 'iwlist' command scans for wireless networks. It requires 'sudo' and your password to pass this system-level command to the wireless driver, or else it will fail.
    $ sudo iwlist eth1 scan
    [sudo] password for ian:    #Your password will not show when you type 
    eth1      Scan completed :
              Cell 01 - Address: 00:14:BF:EB:94:77
                        Frequency:2.437 GHz (Channel 6)
                        Quality=94/100  Signal level=-35 dBm  Noise level=-64 dBm
                        Encryption key:off
                        Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
                                  24 Mb/s; 36 Mb/s; 54 Mb/s; 6 Mb/s; 9 Mb/s
                                  12 Mb/s; 48 Mb/s
    3) Use 'iwconfig' to connect to a network with the essid 'MyNetwork'. This time, you need to also use sudo, since you're telling it to make a system-level change.
    $ sudo iwconfig eth1 essid MyNetwork
         # If it's been less than 15 minutes, the system won't ask for your password again
    4) Let's use 'iwconfig' to check if it worked
    $ iwconfig eth1
    eth1      IEEE 802.11g  ESSID:"MyNetwork"  Nickname:""
              Mode:Managed  Frequency:2.437 GHz  Access Point: 00:14:BF:EB:94:77   
              Bit Rate=54 Mb/s   Tx-Power=27 dBm   
              Retry min limit:7   RTS thr:off   Fragment thr=2346 B   
              Power Management:off
              Link Quality=85/100  Signal level=-51 dBm  Noise level=-85 dBm
              Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
              Tx excessive retries:0  Invalid misc:0   Missed beacon:0
    5) Now that we're connected, let's use 'dhclient3' to get an IP address
    $ sudo dhclient3 eth1
    There is already a pid file /var/run/ with pid 5056
    killed old client process, removed PID file
    Internet Systems Consortium DHCP Client V3.0.6
    Copyright 2004-2007 Internet Systems Consortium.
    All rights reserved.
    For info, please visit
    wmaster0: unknown hardware address type 801
    Listening on LPF/eth1/00:13:02:d0:bd:ce
    Sending on   LPF/eth1/00:13:02:d0:bd:ce
    Sending on   Socket/fallback
    DHCPREQUEST of on eth1 to port 67
    DHCPREQUEST of on eth1 to port 67
    DHCPACK of from
    bound to -- renewal in 42731 seconds.
    Finally, let's run a test to make sure we can use our newly acquired network.
    $ ping
    PING ( 56(84) bytes of data.
    64 bytes from ( icmp_seq=1 ttl=245 time=307 ms
    64 bytes from ( icmp_seq=2 ttl=245 time=306 ms
    64 bytes from ( icmp_seq=3 ttl=245 time=167 ms
    <CTRL+C to stop the pings>
    --- ping statistics ---
    4 packets transmitted, 3 received, 25% packet loss, time 2998ms
    rtt min/avg/max/mdev = 167.460/260.451/307.891/65.759 ms

  3. #3
    Join Date
    Mar 2009

    Re: Ubuntu Server - USB Wireless CLI config

    Thank you for a nicely formed reply.

    But unfortunately there has been some differences with my Pc.
    The interface name is wlan0 and it picks up the USB device I presume since it prints out a nice report on IEEE 802.11bg ESSID: "mySSID". However I get no Link Quality, no signal strenght, no noise level... plain zeros. That is after the "sudo iwconfig wlan0 essid mySSID" command. Even the scan thingy doesn't do anything it simply prints out an unpleasant "Interface doesn't support scanning : network is down". After the dhclient 3 it gives me a few messages stating "Network is down".

    PS: Can you tell me how to copy the output of the commands I type into the PC and how to transfer them onto this PC?

  4. #4
    Join Date
    Jan 2008

    Re: Ubuntu Server - USB Wireless CLI config


    I am aware that this thread is a few months old, but for the benefit of those who will come after your problem of the network being down is solved by simply bringing it up.

    sudo ifconfig "network device (eth0, wlan0, etc)" up
    I am using a Rosewill USB device so my command was

    sudo ifconfig ra0 up
    After this you can run the commands specified before.


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