Linux: add a swap file

To add a swap file:

1. Determine the size of the new swap file and multiple by 1024 to determine the block size. For example, the block size of a 64 MB swap file is 65536.
2. At a shell prompt as root, type the following command with count being equal to the desired block size:
   

   dd if=/dev/zero of=/swapfile bs=1024 count=65536

3. Setup the swap file with the command:
   

   mkswap /swapfile

4. To enable the swap file immediately but not automatically at boot time:
   

   swapon /swapfile

5. To enable it at boot time, edit /etc/fstab to include:
   

   /swapfile swap swap defaults 0 0

   The next time the system boots, it will enable the new swap file.

6. After adding the new swap file and enabling it, make sure it is enabled by viewing the output of the command cat /proc/swaps or free.