Swap Files (If the ram is not enough)

I guess many know this already, but it recently helped me with a lot of problems,
and I guess there are many who don't know how to work with swap on Linux.
So I give a short Howto on Swap-Files

• What is Swap?Swap is a special filesystem in Linux systems which provides the system an alternative memory space if the RAM is full.
• For what can I use it: If your Programs (e.g. Code_Aster) run out of Memory, you can create Virtual RAM for your Programs
• How can I create Swap
2 Possibilities: Create a Swap Partition is the standard way, but what if you only need swap temporarily or simply don't have the user rights? Then you can create a Swapfile.

Do the following steps in a terminal:

1. Work as root-user:

   sudo -i

2. Create an empty file with zeros (here we create swapfile in the root directory with 512 Megabiyte (M) ):

   dd if=/dev/zero of=/swapfile bs=1M count=512

   Explaination: dd makes a file full with zeros in the file swapfile (or what name and location you wish to give; you could also create one in your user directory with of=/home/username/myswapfile) ; bs=1M gives the blocksize. You could also use e.g. 1G for one Gigabyte instead. Count is the number of Blocks. In this case we have 512 blocks with 1 Megabyte, i.e. 512 MB
3. Set the right user rights (not necessary but highly recommended for security reasons):

   chmod 600 /swapfile

4. Activate Swapfile:

   swapon /swapfile

5. Set entry in

   /etc/fstab

   (optional) if you want to keep the file if you reboot the machine:

   /swapfile none swap defaults 0 0

6. To safely remove the swapfile:

   swapoff -a

   to turn it off an then

   rm -rf /swapfile

Thats it. For further reading i Refer to my source in the Arch Linux Wiki

Hope that helps some people!