Disable login password
From MyWiki
Sudo nano /etc/inittab
This will open up the boot time system configuration script.
Scroll down the file until you reach the line ‘1:2345:respawn:/sbin/getty 115200 tty1’
When you see that line, put a hash # in front of it to disable that line then scroll to the end of line and hit enter.
In the blank line that appears add the following command
1:2345:respawn:/bin/login -f pi tty1 / dev/tty1 2>&1