How to add swap space on Ubuntu 20.04

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Swap is space on a hard drive that is used when the physical RAM memory is full. When a Linux system runs out of memory, inactive pages are moved from memory to the swap area.

The swap area can either take the form of a dedicated swap partition or a swap file. When Ubuntu is running on a virtual machine, there is usually no swap partition and the only option is to create a swap file.

This tutorial explains how to add a paging file on Ubuntu 20.04.

before you start

Swap should not be viewed as a substitute for physical storage. Since the swap memory is a section of the hard disk, it has a slower access time than the physical memory. If your system is constantly running out of memory, consider adding more RAM.

In general, the size of the paging file depends on how much RAM your system has:

  • Systems with less than 2 GB of RAM – 2 times the amount of RAM.
  • Systems with 2 to 8 GB of RAM – the same size as the amount of RAM.
  • Systems with more than 8 GB of RAM – at least 4 GB swap.

Only root or users with sudo permissions can activate the swap file.

Create a swap file

In this example we are creating 2 GB Paging file. If you want to add more swap replace it 2G with the amount of swap space you need.

To add swap space on Ubuntu 20.04, do the following:

  1. First, create a file that will be used as a swap:

    sudo fallocate -l 2G /swapfile

    If the fallocate Utility does not exist on your system or you receive an error message stating fallocate failed: Operation not supported, use the following command to create the paging file:

    sudo dd if=/dev/zero of=/swapfile bs=1024 count=2097152
  2. Set the file permissions 600 to prevent normal users from writing and reading the file:

    sudo chmod 600 /swapfile
  3. Create a Linux swap area for the file:

    sudo mkswap /swapfile
    Setting up swapspace version 1, size = 2 GiB (2147479552 bytes)
    no label, UUID=fde7d2c8-06ea-400a-9027-fd731d8ab4c8
    
  4. Activate the paging file by running the following command:

    sudo swapon /swapfile

    To make the change permanent, open that /etc/fstab File:

    sudo nano /etc/fstab

    and insert the following line:

    / etc / fstab
    /swapfile swap swap defaults 0 0
  5. Make sure the swap is active by using either the swapon or the free
    Command as shown below:

    sudo swapon --show
    NAME      TYPE      SIZE  USED PRIO
    /swapfile file        2G    0B   -1
    sudo free -h
                  total        used        free      shared  buff/cache   available
    Mem:          981Mi        97Mi        68Mi       0.0Ki       814Mi       735Mi
    Swap:         2.0Gi        10Mi       1.9Gi

Adjusting the swap value

Swappiness is a property of the Linux kernel that defines how often the system uses the swap area. It can have a value between 0 and 100. A lower value will cause the kernel to try to avoid swapping whenever possible, while a higher value will cause the kernel to use swap space more aggressively.

Under Ubuntu, the default value for swappiness is set to 60. You can check the current value by entering the following command:

cat /proc/sys/vm/swappiness
60

While the swappiness value of 60 is fine for most Linux systems, but may need to be set lower for production servers.

To set the swappiness value, for example, to 10, Run:

sudo sysctl vm.swappiness=10

To make this parameter persistent across reboots, add the following line to the /etc/sysctl.conf File:

/etc/sysctl.conf
vm.swappiness=10

The optimal swappiness value depends on your system utilization and the use of memory. You should adjust this parameter in small steps to find an optimal value.

Remove a paging file

Proceed as follows to deactivate and delete the paging file:

  1. First deactivate the swap space:

    sudo swapoff -v /swapfile
  2. Next, remove the paging file entry /swapfile swap swap defaults 0 0 of the /etc/fstab File.

  3. Finally, remove the actual paging file with the rm
    Command:

    sudo rm /swapfile

diploma

We showed you how to create a swap file and activate and configure the swap area on your Ubuntu 20.04 system.

If you run into any problem or have any feedback, please leave a comment below.

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