First of all you can execute swapon command to check how much swap space you already have in your system
$ swapon -s
Filename Type Size Used Priority
/dev/sda5 partition 8130556 44732 -1
The above output gives you an indication that you already have a swap space at partition /dev/sda5. The numbers under “Size” and “Used” are in kilobytes. Though I have considerable amount of swap space configured on my system :), let’s continue and try to create a new swap using file system. Before starting with creation of swap space let’s make sure that I’ve enough disk space available in my system
$df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 448G 123G 303G 29% /
udev 1.9G 4.0K 1.9G 1% /dev
tmpfs 767M 40M 727M 6% /run
none 5.0M 0 5.0M 0% /run/lock
none 1.9G 804K 1.9G 1% /run/shm
So I’ve a powerful system with 303G of disk space still available, that means I have a liberty of creating a swap space of my liking. I’ll user the data dump(dd) command to my supplementary swap file, make sure that you would be running this command using root user.
$dd if=/dev/zero of=/home/sandy/extraswap bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 2.41354 s, 222 MB/s
Now we have created a file /home/sandy/extraswap of size 512M which we will be using as a swap partition. Swap can be created by issuing mkswap command
$mkswap /home/sandy/extraswap
Setting up swapspace version 1, size = 524284 KiB
no label, UUID=685ac04a-ad31-48a8-83df-9ffa3dbc6982
Finally we have to run swapon command on our newly created swap partition to bring it into the game
$swapon -s
Filename Type Size Used Priority
/dev/sda5 partition 8130556 46248 -1
$swapon /home/sandy/extraswap
$swapon -s
Filename Type Size Used Priority
/dev/sda5 partition 8130556 46248 -1
/home/sandy/extraswap file 524284 0 -2
As you can notice when we first executed the swapon -s command at that time swap partition was not in the picture, once we executed the command swapon /home/sandy/extraswap the swap partition was available.
One last thing that we have to do is to add the entry of this swap partition in our /etc/fstab file as with the next system boot the swap partition will not be active by default we have to do the entry of this swap in our /etc/fstab file.