How to add more Swap Space on Red Hat Linux System if you are left with no free Hard Disk space to create a new partition for Swap

You installed a new Linux system, but forgot to set enough swap space for your needs. Do you need to repartition and reinstall? No, the swap utilities on Linux allow you to make a real file and use it as swap space even if you have no free space to make another swap partition.

The trick is to make a file and then tell the swapon program to use it. Here's how to create, for example, a 512 MB swap file on your root partition (of course make sure you have at least 512 MB free on the filesystem on which you are going to create it):

#dd if=/dev/zero of=/swapfile bs=1024 count=524288

This will make a 512 MB file on your hard drive. You now need to initialize it:

#mkswap /swapfile 524288
#sync

And you can then add it to your swap pool:

#swapon /swapfile

With that you have 512 MB of swap added. Don't forget to add the swapon command to your startup files so the command will be repeated at each reboot.