raspberry pi for dummy: WPA_SUPPLICANT: /SBIN/WPA_SUPPLICANT DAEMON FAILED TO START

Monday, 27 March 2017 UPDATE:
- please refer to this official Raspberry Pi Wifi configuration documentation

After you have the USB Wifi dongle plugged into your RPI, you can scan wifi sign near you with

sudo iwlist wlan0 scan 

command (if this work, that mean you are close to setup wifi successfully)

Finally, if you haven't added any network config in your wpa_supplicant.conf (/etc/wpa_supplicant/wpa_supplicant.conf) insert wifi detail using:

wpa_passphrase "your wifi SSID" "your wifi password" >> /etc/wpa_supplicant/wpa_supplicant.conf

Note: please refer official link attached above for detailed explanation.

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If you face problems stated below:
- WPA_SUPPLICANT: /SBIN/WPA_SUPPLICANT DAEMON FAILED TO START

You may first look at this Setting up Wifi (EDIMAX) on Raspberry Pi,
if you're still fail to configure a successful connection to your access point (AP or wifi router),

please remove the quote symbol to your psk value like this in your wpa_supplicant.conf:

network={
    ssid="Your SSID Here"
    key_mgmt=WPA-PSK
    psk=YourPresharedKeyHereWithoutQuote
}

get your PSK value from WireShark WPA-PSK Generator.

Once done:
apply commands and restart network or your RPI (sudo reboot):

sudo service networking restart
sudo ifup wlan0 (or sudo ifdown wlan0 then sudo ifup wlan0)

I wrote this because I saw too many tutorial out there didn't mention/emphasize about removing the quote symbol for psk value.
examples

Circled quotes symbols should not be around your psk value

wireless setup command reference: Useful Linux Wireless Commands