Change the swap memory size in Raspeberry

I've been puzzled by a failure in the Rails on Ruby setup inside the Pi. After searching I found this page and it works fine:
Raspbian uses dphys-swapfile, which is a swap-file based solution instead of the "standard" swap-partition based solution. It is much easier to change the size of the swap.

• The configuration file is:

/etc/dphys-swapfile 

• The content is very simple. By default my Raspbian has 100MB of swap:

CONF_SWAPSIZE=100

• If you want to change the size, you need to modify the number and restart dphys-swapfile:

/etc/init.d/dphys-swapfile stop
/etc/init.d/dphys-swapfile start

 
The last step didn't work for me. Instead, I had to restart the Pi.

Configuring the RPi B+ default serial port

By default Raspbian configures the Raspberry Pi serial port (GPIO14-GPIO15) to provide boot-up information. It also allows you to login via a connected device. If you need to use the Pi’s serial port for something else (i.e. a specific add-on board) you will need to disable this default functionality.

The Broadcom UART appears as /dev/ttyAMA0 under Linux. There are several minor things in the way if you want to have dedicated control of the serial port on a Raspberry Pi. This link describes the process for free the serial port: http://elinux.org/RPi_Serial_Connection. There is a brief script to automate the same steps: https://github.com/lurch/rpi-serial-console.

If you want to test the serial port to send/receive data:

• First have a look at the permissions on that file, lets assume you are using /dev/ttyAMA0:

ls -l /dev/ttyAMA0

• You will want read.write access, if this is a shared system then you should consider the security consequences of opening it up for everyone:

chmod o+rw /dev/ttyAMA0

• You have to setup the baud rate with the next instruction:

 stty 115200 -F /dev/ttyAMA0

• A very simple crude method to write to the file (send data to the serial port), would use the simple echo command in one terminal:

echo -ne 'ri_07_02' > /dev/ttyAMA0

• And to read use the minicom command (maybe with another terminal):

minicom -b 115200 -o -D /dev/ttyAMA0