I have flashed Erle-Brain-3-frambuesa-update-04-07-2017.img to the 16 GB SD card. After the flash it created root and boot partitions, But there is a 7.43GB disk space is showing as unallocated. How we can make use of that space as a part of "/"?
You can use GParted and make the following:
Select the ext4 partition > Resive/Move > and move it to the right > and press the button that says Resize/Move.
After that you have to click on the green check.