File-based Swap for Linux
You forgot to create a swap filesystem on Linux, and you don’t know or don’t want to use fdisk to repartition a disk and create swap space.
What do you do?
Fortunately, you still have a chance of saving your job.
1. Logon as root
2. Create a new directory anywhere that you prefer to use as swap fs. I prefer creating under the root directory and name it as /swapfs
mkdir /swapfs
3. We will create a data dump of a bunch of zeroes and store it in a X-bytes worth of file. The X-bytes will represent the size of swap file that you want or need. What is the ideal size? My answer has always been, it depends! If its just your PC for browsing the internet etc…, same size with your RAM will do. If its a database server, you may not want to use swap intensively, so blow up your RAM instead. I typically benchmark it from half of my RAM, to even twice my RAM. Again, it depends on what type application is running on your server or PC.
dd if=/dev/zero of=/swapfs/swap bs=1M count=4096
I am creating here a 1 megabyte swap file. It will create a file named swap under the directory /swapfs
4. I’ll now assign /swapfs/swap file as a SWAP space
mkswap /swapfs/swap
5. Of course, that is not enough, you have to enable it
swapon /swapfs/swap
If you’ll issue a df command, you’d be able to see the new swap filesystem, and the top command will also display the additional swap space.
