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How to Add a Swap File On Ubuntu

A swap file in Ubuntu is a dedicated file on the hard drive that is used as virtual memory when RAM is full. It enhances system performance by providing additional space for temporarily storing data that is not actively used by the CPU. A swap file should only be used when you need swap space, and a swap partition can not be added.

This article guides you through adding a swap file to your Ubuntu system, a flexible alternative to creating a dedicated swap partition.

Creating the Swap File

First, decide on the size of your swap file. A general recommendation is to make it equal to or double the amount of RAM for systems with less than 4GB of RAM. For systems with more RAM, a swap size equal to the amount of RAM might be sufficient.

Use the fallocate command to create a swap file of the desired size. For example, to create a 4GB swap file, you would use:

sudo fallocate -l 4G /swapfile

Setting the Swap File Permissions

For security reasons, the swap file must not be readable by any user other than root. Set the correct permissions using the `chmod` command:

sudo chmod 600 /swapfile

Formatting the Swap File

Next, format the file to be used as swap space:

sudo mkswap /swapfile

Activating the Swap File

To start using the swap file immediately, activate it with:

sudo swapon /swapfile

Making the Swap File Permanent

To ensure the swap file is used on system boot, edit the `/etc/fstab` file:

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

Checking Your Swap File

To confirm that your swap is active, use:

sudo swapon --show

Or you can use:

free -h

To view the overall memory and swap usage.

Frequently Asked Questions

How do I determine the optimal size for my swap file?

The optimal size depends on your system configuration and usage. For systems with less RAM, a larger swap can be beneficial. In general, an amount equal to or double your RAM is a good starting point.

Can I have multiple swap files or a combination of swap files and swap partitions?

Linux supports multiple swap spaces, which can be a combination of swap files and swap partitions.

How do I remove a swap file?

To remove a swap file, first deactivate it with:

sudo swapoff /swapfile

Then remove the file using

sudo rm /swapfile

Don’t forget to remove the corresponding entry from /etc/fstab file.

Will adding a swap file slow down my system?

Swap space is typically slower than RAM. However, it provides a necessary buffer for when your RAM is fully utilized. Properly configured swap space should not noticeably slow down your system under normal operations.

Is a swap file as effective as a swap partition?

Swap files and swap partitions offer similar performance in modern Linux kernels. The choice between them often comes down to flexibility and ease of management, with swap files generally being easier to create and modify.


Adding a swap file in Ubuntu Linux can significantly benefit your system’s performance and stability, especially under high-load conditions. By following these steps, you can ensure that your system has enough “breathing room” to handle intensive applications and multitasking scenarios. Remember to monitor your system’s performance and adjust your swap settings as needed.



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