Swap space in Linux acts as an “overdraft” when your system runs low on physical memory (RAM). It provides a backup system, allowing the operating system to move less-used pages of memory over to the swap space, freeing up main memory for other, more pressing tasks. Here’s how to check the amount of swap space currently in use and how to manage it.
Checking Swap Space
You can check the amount of swap space your system is currently utilizing with the swapon command. This command will list all swap areas currently in use:
swapon --show
Adding Swap Space
If you find that you need more swap space, you can add more. The first step is to create a file that will be used for swap:
sudo fallocate -l 1G /swapfile
This command will create a 1GB file at /swapfile for swap space. You can replace “1G” with the amount of swap space you want to add.
Next, set the correct permissions for the swap file:
sudo chmod 600 /swapfile
Then, tell the system to set up a swap area on the file:
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And finally, make the system start using the swap file:
sudo swapon /swapfile
Persisting Swap File
To make the swap file persist across reboots, you need to add it to the /etc/fstab file:
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
Note that creating too large a swap space can lead to system degradation, as important system resources could be swapped out, leading to slow access times. As a general rule, your swap space should be equal to or at most 2 times the amount of physical RAM on your system.
Removing Swap Space
If you want to reduce the amount of swap space, you can deactivate and remove the swap file. First, turn off the swap space:
sudo swapoff /swapfile
Then remove the swap space file:
sudo rm /swapfile
Finally, remove the related line in the /etc/fstab file.
Conclusion
Understanding and managing swap space is one of the basic skills that every Linux user should know. It allows you to maintain optimal performance and manage your system resources more efficiently. Remember that while the swap space can be a lifesaver in times of memory shortage, it is not a substitute for more RAM.
