How to add Swap Space on Ubuntu 20.04

How to add Swap Space on Ubuntu 20.04

As an administrator, you have face out-of-memory errors in applications. In this article, we are going to learn you how to add Swap Space on Ubuntu 20.04. Join us to review how easy you can guard against this issue after adding swap space to your server.


How to add Swap Space on Ubuntu 20.04

What is Swap?

While RAM can not hold some data anymore, there is an area on the hard drive that is specified as a place where the operating system can temporarily store data. This area is called Swap. In other words, when there is no longer sufficient space in RAM to hold in-use application data, you are able to increase the amount of information that your server can keep in its working “memory”.

Although the written information to disk will be slower (than information kept in RAM), the operating system will prefer to keep running application data in memory and use swap.

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 1- Checking the System for Swap Information

First, check the system for any swap space available. One should be enough, though it is possible to have multiple swap files or swap partitions,

To verify this, type below command

sudo swapon --show

In case you do not receive any output, it means the system has no swap space available currently.

To check if there is any active swap or not, use free utility

free -h    Output                  total        used        free      shared  buff/cache   available  Mem:          990Mi        36Mi       863Mi       4.0Mi        89Mi       837Mi  Swap:            0B          0B          0B        

2- Checking Available Space on the Hard Drive Partition

To check your current disk usage to make sure you have enough space, enter the following command.

df -h
Filesystem      Size  Used Avail Use% Mounted on  udev            488M     0  488M   0% /dev  tmpfs           100M  4.5M   96M   5% /run  /dev/vda1        25G  989M   23G   5% /  tmpfs           499M     0  499M   0% /dev/shm  tmpfs           5.0M     0  5.0M   0% /run/lock  tmpfs           499M     0  499M   0% /sys/fs/cgroup  tmpfs           100M     0  100M   0% /run/user/1001


3- Creating a Swap File

Now you can create a swap file on your file system as you know your available hard drive space. To create a swap file use fallocate program to creates a file of the specified size. You need to create a 1G file while the server in the below example has 1G of RAM.

sudo fallocate -l 1G /swapfile  

To verify the correct amount of space is reserved, enter the below command.

ls -lh /swapfile
-rw-r--r-- 1 root root 1.0G May 29 17:34 /swapfile

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4- Enabling the Swap File

While the file has the correct size, you should turn this into swap space. To let the only users with root privileges can read the contents, lock down the permissions of the file.

Use the following command, to make the file only accessible to root,

sudo chmod 600 /swapfil  

If you want to check the permissions change, type the below command.

ls -lh /swapfile  
-rw------- 1 root root 1.0G May 29 17:34 /swapfile

Mark the file as swap space by typing:

sudo mkswap /swapfile  
Setting up swapspace version 1, size = 1024 MiB (1073737728 bytes)  no label, UUID=b591444e-c12b-45a6-90fc-e8b24c67c006f

You can enable the swap file after marking the file to allow the system to start using it.

sudo swapon /swapfile

To check the swap is available or not, enter the following command.

sudo swapon --show  
NAME      TYPE  SIZE USED PRIO  /swapfile file 1024M   0B   -2

You can check the output of the free utility again to corroborate your findings:

free -h  
              total        used        free      shared  buff/cache   available  Mem:          990Mi        37Mi       860Mi       4.0Mi        92Mi       834Mi  Swap:         1.0Gi          0B       1.0Gi


5- Making the Swap File Permanent

The recent change enabled the swap file for the current session. If you reboot, the server will not retain the swap setting automatically. To change this, add the swap file to your /etc/fstab file.

If you faced anything goes wrong, back up the /etc/fstab

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

Using the below command, add the swap file information to the end of your /etc/fstab file.

echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab  

6- Tuning your Swap Settings

To configures how often your system swaps data out of RAM to the swap space, you can use the swappiness parameter. You can see as a value between 0 and 100 that represents a percentage. The values that are closer to 100 will try to put more data into swap in an effort to keep more RAM space free.

You can see the current swappiness value by typing:

cat /proc/sys/vm/swappiness  

Also, you can set the swappiness to a different value by using the sysctl command.

To set the swappiness to 10, you could type:

sudo sysctl vm.swappiness=10  
vm.swappiness = 10

You can set this value automatically at restart by adding the line to your /etc/sysctl.conf file

sudo nano /etc/sysctl.conf

Also, you could add:



Now save and close the file when you are finished.


You can also modify the vfs_cache_pressure, to configure how much the system will choose to cache inode and dentry information over other data. However, this is access data about the filesystem and is very costly to look up and very frequently requested. To check the current value by querying the proc filesystem again:

cat /proc/sys/vm/vfs_cache_pressure  

You can set this to a more conservative setting like 50 by typing:

sudo sysctl vm.vfs_cache_pressure=50  

Also, you can change that by adding it to our configuration file.

sudo nano /etc/sysctl.conf  

And finally, add the line that specifies your new value:



Then save and close the file, when you are finished.


Recommended Article: How to add Swap Space on Ubuntu 20.04

Dear user, we hope you would enjoy this tutorial on how to add Swap Space on Ubuntu 20.04 you can ask questions about this training in the comments section or to solve other problems in the field of Eldernode training, refer to the Ask page section and raise your problems in it.



Also, see

How to clear cache buffer and swap memory in Linux

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