Default entry for /etc/network/interfaces

Question

I accidentally removed everything inside my laptop's /etc/network/interfaces file. Now it does not find any WiFi network/SSID

I Tried to change to this but it still has problem:

auto lo
Iface lo inet loopback

auto wlan0
iface wlan0 inet dhcp

Then I do

$ ifup wlan0

But it gets stuck and prints the following line forever:

DHCPDISCOVER on wlan0..........

Answer 1

If you wish to continue with /etc/network/interfaces, wireless will require the addition of the network you intend to connect to and any encryption details. I suggest:

auto lo
iface lo inet loopback

auto wlan0
iface wlan0 inet dhcp
wpa-ssid mynetwork
wpa-psk 0123456789

Restart the interface:

sudo ifdown wlan0 && sudo ifup -v wlan0

Check:

ping -c3 www.ubuntu.com

Answer 2

Did you try restarting network-manager after adding back the file content?

sudo restart network-manager

Answer 3

Add to /etc/network/interface the following code:

auto lo

iface lo inet loopback

Then save the file and run the command:

sudo restart network-manager - as el_tigro stated.

This should reactivate the network interface and allow you to connect to the internet again.