How to add Swap File
Follow these steps to add 1GB of swap to your server. If you want to add 2GB instead of 1 GB, replace 1G with 2G.
1. Create swap file
Create a file that will be used for swap:
sudo fallocate -l 1G /swapfile
"Note: dynamic space allocation such as using fallocate is not supported, as it causes problems with some file systems such as F2FS[1] and will likely fail to activate at boot time with error "swapon: swapfile has holes" as of kernel 5.7. Hence, contiguous allocation, such as dd, is the only reliable way to allocate a swap file.[2]" (https://wiki.archlinux.org/index.php/Swap#Swap_file).
If fallocate is not installed or if you get an error message saying fallocate failed: Operation not supported then you can use the following command to create the swap file:
sudo dd if=/dev/zero of=/swapfile bs=1024 count=3145728
2. Change ownership
Only the root user should be able to write and read the swap file. To set the correct permissions type:
sudo chmod 600 /swapfile
3. Set file as swap area
Use the mkswap utility to set up the file as Linux swap area:
sudo mkswap /swapfile
4. Enable swap
Enable the swap with the following command:
sudo swapon /swapfile
5. Set swap in fstab
To make the change permanent open the /etc/fstab file and append the following line:
/swapfile swap swap defaults 0 0
6. Verify
To verify that the swap is active, use either the swapon or the free command as shown below:
swapon:
sudo swapon --show
NAME TYPE SIZE USED PRIO
/swapfile file 1024M 507.4M -1
free:
sudo free -h
total used free shared buff/cache available
Mem: 488M 158M 83M 2.3M 246M 217M
Swap: 1.0G 506M 517M
7. Adjust swappiness value
How to adjust the swappiness value
Swappiness is a Linux kernel property that defines how often the system will use the swap space. Swappiness can have a value between 0 and 100. A low value will make the kernel to try to avoid swapping whenever possible, while a higher value will make the kernel to use the swap space more aggressively.
The default swappiness value is 60. You can check the current swappiness value by typing the following command:
cat /proc/sys/vm/swappiness
60
While the swappiness value of 60 is OK for most Linux systems, for production servers, you may need to set a lower value.
For example, to set the swappiness value to 10, you would run the following sysctl command:
sudo sysctl vm.swappiness=10
To make this parameter persistent across reboots append the following line to the /etc/sysctl.conf file:
vm.swappiness=10
The optimal swappiness value depends on your system workload and how the memory is being used. You should adjust this parameter in small increments to find an optimal value.
8. Remove Swap File
If for any reason you want to deactivate and remove the swap file, follow these steps:
First, deactivate the swap by typing:
sudo swapoff -v /swapfile
Remove the swap file entry /swapfile swap swap defaults 0 0 from the /etc/fstab file.
Finally, delete the actual swapfile file using the rm command:
sudo rm /swapfile