Creating a swap file

From CLUG Wiki

Did you forget to create a swap partition, and now you dont want to repartition to add it? Just an a swap file. This is how:

• 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.

• 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

• Setup the swap file with the command:

 mkswap /swapfile

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

 swapon /swapfile

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

 /swapfile               swap                    swap    defaults        0 0

• 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.

 root@mail[~]# free
              total       used       free     shared    buffers     cached
 Mem:        119400     115956       3444          0       2240      64464
 -/+ buffers/cache:      49252      70148
 Swap:       262132      14300     247832
 root@mail[~]#

Taken from here