I had a requirement to run a headless Linux device, coupled with a 3G USB dongle for communications. The Raspberry Pi 3 I bought about 9 months back came in handy.
Here are the steps I took to setup Linux on Rpi.
1. Download and copy the Linux image file onto a micro SD card.
2. Insert the micro SD card into the Rpi and start it up with the keyboard and mouse connected.
3. Log in, and run ‘sudo apt-get update’
4. Update gparted to expand the partition space. You will need to apt-get install gparted
5. Run gparted and expand the existing partition space.
7. Insert the following string into the /boot/cmdline.txt file. ‘usbhid.mousepoll=0’ at the end of the string. This step removes the laggy mouse scroll.
8. Insert the two following lines into /boot/config.txt file ‘dtoverlay=pi3-disable-wifi’ and ‘dtoverlay=pi3-disable-bt’ at the end of the file. Each lines on their own. This step disables the wifi and bluetooth.
10. Insert 3G Dongle and update the APN configuration in network-manager.
11. APN: hicard, Username: