How to allow customisations if Raspbian is already installed?

[mukkachaitanya]

I run my RaspPi headless and by mistake changed my /etc/network/interfaces which rendered my WiFi not working. So I was thinking if these customisations work with pre-installed Raspbian too ?

[procount]

Did you install Raspbian via NOOBS?
What version of NOOBS do you have?
What model of Pi do you have?
What wifi dongle do you use?
Can you use an Ethernet connection?
Can you access NOOBS headlessly (via ethernet, or wifi if you have a broadcom wifi chipset)?

[mukkachaitanya]

Yes I have installed Raspbian via NOOBS.
Not sure about NOOBS version.
Raspberry Pi2
I am not sure about its company. But it's not one of those official ones.

BTW I was able to edit my interfaces, and made required changes. But I have a new problem that when I plug usb dongle the system freezes and the red lights start blinking erratically.

[procount]

It's good that you managed to edit your interface file. Does that mean that you managed to put it back in your Raspbian image too? In which case you are sorted with that.

Your new problem sounds like a power supply issue. A blinking red LED means your Pi is not getting enough voltage. Try a more powerful power supply, a shorter thicker cable, or plug your wifi dongle into a powered USB hub. You can also try adding max_usb_current=1 to your config.txt file to ensure your wifi
dongle is getting enough current.

[mukkachaitanya]

I am not sure if it's a problem with the power supply, because the pi worked perfectly with the dongle earlier (i.e. before I messed up the interfaces file). Also I'm not sure even if ethernet is working as pi doesn't take up an IP when connected to it.

PS I will try changing max_usb_current value.

[procount]

You're probably better off posting this issue on the RPi forums to get a broader response.

It's also better to connect your wifi dongle before applying power to avoid power fluctuations.