How To Create Swap on Ubuntu Step By Step


The simple way of increasing the responsiveness of your server  against out of memory errors in server  to add some swap space. In this artical, we will help how to create a swap file to an Ubuntu 16.04 &18.04 &19.04 server.

What is Swap?

The Linux Kernel usually uses your RAM memory to store temporary information.When there is no enough RAM space, the Linux Kernel takes some of this information from RAM and writes it to the swap space on a hard drive.

This is called the swapping process. This way your Linux system can release some RAM space.and doesn’t crash due to lack of memory. So, Linux swap is a very useful way to extend the RAM because it provides the necessary

additional memory when the RAM space has been exhausted and a process has to be continued.

Check the System for Swapspace Information

You can check type  of your Swapspace with this command:

$ sudo swapon --show

If you are not getting any output that means no swapspace available on your system currently.

You can verify no active swap using the free command

$ free -h

Out Put

[email protected]~$ swapn
total       used       free     shared    buffers     cached
             total       used       free     shared    buffers     cached
Mem:          1518       1459         59          0        180        631
-/+ buffers/cache:        647        871
Swap:         2047          0       2047

Check Available Space on the Hard Drive Partition

Before start first check the current disk space using this command

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            2.0G     0  2.0G   0% /dev
tmpfs           395M  776K  394M   1% /run
/dev/xvda1       25G   11G   14G  44% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/loop1       89M   89M     0 100% /snap/core/7396
tmpfs           395M     0  395M   0% /run/user/1000

/dev/xvda1 is our disk in this case

Create a Swap File

create a swap file, run this command first and replace 2G with the value you want.

$sudo fallocate -l 2G /swapfile

You can verify that correct amount space reserved  for swap memory

$ ls -lh /swapfile

-rw------- 1 root root 2.0G Aug 26 18:25 /swapfile


Finally, Enable The Swap.

You have to set the correct permissions of the file so that only the root privileges can read the contents

Set  the file permission only accessible to root user  by typing:

sudo chmod 600 /swapfile

Check permissions  typing this command:

ls -lh /swapfile

-rw------- 1 root root 2.0G Aug 26 18:25 /swapfile

Then mark the file as swap  by typing this command:

$ sudo mkswap /swapfile
Setting up swapspace version 1, size = 2048 MiB (2147483648 bytes)
no label, UUID=6e755505-3ab8-450g-aed3-596e7608sdge

You can enable swapfile using typing this command:

$ sudo swapon /swapfile

Verify Swapspace is enable or not typing this command:

$ sudo swapon --show

/swapfile file   2G   0B   -2

You can verify the output usefree utility command :

$ free -h
              total        used        free      shared  buff/cache   available
Mem:           3.9G        2.7G        382M        2.4M        836M        980M
Swap:          2.0G          0B        2.0G

Make the Swap File Permanent

First, Back up the /etc/fstab file in if any case anything goes wrong:

$ sudo cp /etc/fstab /etc/fstab.bak

If you want the changes to be permanent, you need to edit the /etc/fstab file open it  and add the following.

/swapfile none swap sw 0 0

Ctrl+O to save the changes and Ctrl+X to exit

In the end, check the status of the swapfile:

$free -h
              total        used        free      shared  buff/cache   available
Mem:           3.9G        2.7G        377M        2.4M        837M        976M
Swap:          2.0G          0B        2.0G

Define How Often The Swapspace Will Be Used.

So, every time your system need to use Swapspace, you will notice that some processes and applications will run slower. However, you can adjust the system to use much more RAM than swap. This can help improve overall system performance. Normally, the default swappiness value is 60.The smaller this value, the more of your RAM will be used. Swap tendency is defined by this formula.

So, to check your current the swappiness value, run this command:

$ cat /proc/sys/vm/swappiness

You should see the value of 60.

If you want to modify the default value, you need to edit the file /etc/sysctl.conf.

And add the following:


10 is the most commonly recommended value.

Also, this setting is recommended when you have more than 2Gb of RAM.

Save the file and close it with Ctrl+O and Ctrl+X keys shortcuts. In order to apply the changes, you need to reboot the system. Now, the swappiness values is ten,This way your Linux kernel will use more RAM and less swap.

All Done Enjoy 🙂

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