ArchLinux connecting to wireless through CLI [WPA]

# iwlist wlan0 scan
Cell 01 - Address: 04:25:10:6B:7F:9D
                    Channel:2
                    Frequency:2.417 GHz (Channel 2)
                    Quality=31/70  Signal level=-79 dBm  
                    Encryption key:off
                    ESSID:"dlink"
                    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; 18 Mb/s; 24 Mb/s
                              36 Mb/s; 48 Mb/s; 54 Mb/s

• If using WPA encryption:

Using WPA encryption requires that the key be encrypted and stored in a file, along with the ESSID, to be used later for connection via wpa_supplicant. Thus, a few extra steps are required:

For the purpose of simplifying and backup, rename the default wpa_supplicant.conf file:

# mv /etc/wpa_supplicant.conf /etc/wpa_supplicant.conf.original

Using wpa_passphrase, provide your wireless network name and WPA key to be encrypted and written to /etc/wpa_supplicant.conf.

The following example encrypts the key “my_secret_passkey” of the “linksys” wireless network, generates a new configuration file (/etc/wpa_supplicant.conf), and subsequently redirects the encrypted key, writing it to the file:

# wpa_passphrase linksys "my_secret_passkey" > /etc/wpa_supplicant.conf

Check WPA Supplicant for more information and troubleshooting.

Note: /etc/wpa_supplicant.conf is stored in plain text format. This is not risky in the installation environment, but when you reboot into your new system and reconfigure WPA, remember to change the permissions on /etc/wpa_supplicant.conf (e.g. chmod 0600 /etc/wpa_supplicant.conf to make it readable by root only).

• Associate your wireless device with the access point you want to use. Depending on the encryption (none, WEP, or WPA), the procedure may differ. You need to know the name of the chosen wireless network (ESSID).

Encryption	Command
No Encryption	iwconfig wlan0 essid “linksys”
WEP w/ Hex Key	iwconfig wlan0 essid “linksys” key “0241baf34c”
WEP w/ ASCII passphrase	iwconfig wlan0 essid “linksys” key “s:pass1”
WPA	wpa_supplicant -B -Dwext -i wlan0 -c /etc/wpa_supplicant.conf

Note: The network connection process may be automated later by using the default Arch network daemon, netcfg, wicd, or another network manager of your choice.

• After utilizing the appropriate association method outlined above, wait a few moments and confirm you have successfully associated to the access point before continuing, e.g.:

# iwconfig wlan0

Output should indicate the wireless network is associated with the interface.

• Request an IP address with /sbin/dhcpcd <interface>, e.g.:

# dhcpcd wlan0

• Lastly, ensure you can route using /bin/ping:

# ping -c 3 www.google.com
PING www.l.google.com (74.125.224.146) 56(84) bytes of data.
64 bytes from 74.125.224.146: icmp_req=1 ttl=49 time=87.7 ms
64 bytes from 74.125.224.146: icmp_req=2 ttl=49 time=87.0 ms
64 bytes from 74.125.224.146: icmp_req=3 ttl=49 time=94.6 ms

--- www.l.google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 87.052/89.812/94.634/3.430 ms

SOURCE: From the great ArchLinux wiki at https://wiki.archlinux.org/index.php/Beginners%27_Guide#Setup_wireless_in_the_live_environment_.28optional.29