Sometimes its useful to connect to Wireless Networks using console . The reasons for that might be many, one possible reason is to be able to debug, Wireless connection failures or simply omit the use of the many available GUI wifi connection programs.
As a first step before connecting in terminal is to look up for the wifi networks available for connection, this is done with cmd:
linux:~# iwlist wlan0 scanning
wlan0 Scan completed :
Cell 01 - Address: 00:24:01:90:8F:38
Channel:7
Frequency:2.442 GHz (Channel 7)
Quality=70/70 Signal level=-39 dBm
Encryption key:on
ESSID:"magdanoz"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s
Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s; 18 Mb/s
24 Mb/s; 36 Mb/s; 54 Mb/s
Mode:Master
Extra:tsf=000000034f5c786b
Extra: Last beacon: 68ms ago
IE: Unknown: 00086D616764616E6F7A
IE: Unknown: 010482848B96
IE: Unknown: 030107
IE: Unknown: 32080C1218602430486C
IE: Unknown: CC0700CC020000018A
IE: Unknown: CC0700CC0300000100
IE: WPA Version 1
Group Cipher : TKIP
Pairwise Ciphers (2) : TKIP CCMP
Authentication Suites (1) : PSK
IE: IEEE 802.11i/WPA2 Version 1
Group Cipher : TKIP
Pairwise Ciphers (2) : TKIP CCMP
Authentication Suites (1) : PSK
Cell 02 - Address: 00:1E:2A:60:5E:DC
Channel:1
...
To just list the ESSID s of the wifi networks:
linux:~# iwlist wlan0 scanning|grep -i 'essid'
ESSID:"magdanoz"
ESSID:"default"
ESSID:"todorov"
ESSID:"BTC-ADSL"
ESSID:"Zahari"
ESSID:"Drago"
1. Connecting to Open Wireless Network
Now from the above output it is clear 6 wifi networks are available for connection. The default wifi network from the list is an Open network (e.g. without pass). To connect to it I use cmd:
linux:~# /sbin/iwconfig wlan0 essid 'default'
linux:~# /sbin/iwconfig wlan0 key open
After connected to configure IP, Gateway and DNS from a DHCP server running on the WIFI router, dhclient cmd is used:
linux:~# /sbin/dhclient wlan0
2. Connecting to WEP 64bit / 128bit encrypted network
linux:~# /sbin/iwconfig wlan0 key 1234-5678-9101-1213
3. Connecting to WPA / WPA2 encrypted wifi network
To connect to WPA or WPA2 encrypted network its necessery to have installed wpasupplicant package. The name of the package might vary in different distributions on Debian and Ubuntu, the name of the package is wpasupplicant, on Fedora, CentOS and RHEL the package that has to be in is wpa_supplicant :
After having installed the wpa_supplicant to connect to the network with ESSID name magdanoz , wpa_passphrase is used first:
linux:~# /usr/bin/wpa_passphrase magdanoz Secret_Wifi_Password | tee -a /etc/wpa_supplicant.conf
network={
ssid="magdanoz"
#psk="Secret_Wifi_Password"
psk=6f7590250c4496ff7bf8dd25199ac3bb5a614d4bc069975aa884bcf084da73bc
}
As you see in above command the secret password key is generated printed on the screen and then added to /etc/wpa_supplicant.conf , necessery to establish the wireless connection with wpa_supplicant with cmd:
linux:~# /sbin/wpa_supplicant wpa_supplicant -d wext -i wlan0 -c /etc/wpa_supplicant.conf -B
-d wext instructs wpa_supplicant to use (Linux wireless extension driver).
-B tells wpa_supplicant to background the connection to prevent the wireless connection to drop off, if the console / terminal from which it is launched gets closed.
In case of succesful connection with wpa_supplicant , once again IP, Gateway and DNS is configured fetching the settings from the wifi hotspot dhcp server:
linux:~# /sbin/dhclient wlan0
General information about the wireless network and info related to the established connection can be obtained with /usr/bin/iwconfig :
linux:~# /sbin/iwconfig
lo no wireless extensions.
eth0 no wireless extensions.
wlan0 IEEE 802.11abg ESSID:"magdanoz"
Mode:Managed Frequency:2.442 GHz Access Point: 00:24:00:90:8F:38
Bit Rate=54 Mb/s Tx-Power=15 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=70/70 Signal level=-39 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
To configure the exact channel over which the wireless connection will be established again is done with iwconfig, for instance to configure wlan0 wifi connection established to be on wifi channel 7:
linux:~# /sbin/iwconfig wlan0 channel 11
By default iwconfig is set to automatically set the channel based on connected network ESSID , if the channel is modified to some specific number to revert it back use:
linux:~# /sbin/iwconfig wlan0 channel auto
