This is a quick guide to adding emergancy swap space to linux. Which is useful when you know a machine is going to run out memory. Or you need a lot of memory for a single task that cannot be completed without the extra memory.

Step 1

Login as root

Step 2

Create a new file of the size that you want to add using the following command. In this case 512 mbytes of space.

dd if=/dev/zero of=/extraswap1 bs=1024 count=512k

Step 3

Fix the permissions on the file so that only the creator can read / write to it.

chmod 0600 /extraswap1

Step 4

Turn it into a swap file and tell linux to turn on the extra space

mkswap /extraswap1

swapon /extraswap1

Step 5

If you want the swap to be enabled after the next reboot of the machine you will need to add the following line to /etc/fstab

/extraswap1 swap swap defaults 0 0

Finally

You can verify that it is working by either using free or by looking directly at the proc filesystem using cat /proc/swaps