How to use the command dphys-swapfile (with examples)

This article will illustrate different use cases of the dphys-swapfile command on Debian-based Linux systems. The dphys-swapfile command is used to manage the swap file, which is a space on the hard drive used by the operating system as virtual memory when the physical memory (RAM) is all in use.

Disable the swap file

Code:

sudo dphys-swapfile swapoff

Motivation: Disabling the swap file can be useful in scenarios where you want to reduce disk I/O or free up disk space temporarily. For example, if your system is running low on free disk space, you can disable the swap file to reclaim some space.

Explanation: The swapoff option is used to disable the swap file. When executed with sudo, the command requires administrator privileges.

Example output:

Stopping dphys-swapfile swapfile setup ...
swapoff for /var/swap.1

Enable the swap file

Code:

sudo dphys-swapfile swapon

Motivation: Enabling the swap file is necessary if you have previously disabled it and want to restore the functionality of virtual memory. The swap file is used to prevent the system from running out of memory when the physical RAM is depleted.

Explanation: The swapon option is used to enable the swap file. When executed with sudo, the command requires administrator privileges.

Example output:

Activating dphys-swapfile swapfile setup ...
swapon for /var/swap.1

Create a new swap file

Code:

sudo dphys-swapfile setup

Motivation: Creating a new swap file can be beneficial when you need to allocate additional virtual memory to your system. This is useful if you frequently run memory-intensive applications or experience high memory usage.

Explanation: The setup option is used to create a new swap file. When executed with sudo, the command requires administrator privileges. The command will automatically configure the swap file with default settings.

Example output:

Want me to create a swap file of size 1024MBytes?
[Y/n] Y
Creating swap file /var/swap.1, size 1024MBytes
1024MiB swapfile has been set up, you must activate it manually using swapon

Conclusion:

The dphys-swapfile command provides easy management of the swap file on Debian-based Linux systems. You can disable the swap file to reduce disk I/O or free up disk space temporarily. Enabling the swap file is necessary to restore virtual memory functionality, and creating a new swap file allows for additional memory allocation on the system. By utilizing these different use cases of the dphys-swapfile command, you can optimize the memory usage and performance of your Linux system.