How to enable swap on Linux server?

Question

A minimum of 1 GB swap is required for Plesk on a Linux server. According to this article, Plesk does not manage swap space. This article describes how to manually enable the swap file in the Linux operating system.

Answer

1. Start by creating a file that will be used for swap:

   # fallocate -l 1G /swapfile

2. Note: In old distributions like CentOS 7 you might have problems with fallocate command, to create the file in sthis case use:

   # dd if=/dev/zero of=/swapfile count=1024 bs=1MiB

3. Only the root user should be able to write and read the swap file. Set the correct permissions by typing:

   # chmod 600 /swapfile

4. Use the mkswap utility to set up a Linux swap area on the file:

   # mkswap /swapfile

5. Activate the swap file using the following command:

   # swapon /swapfile

6. To make the change permanent open the /etc/fstab file:

   # vi /etc/fstab

7. Add the following content:

   CONFIG_TEXT: /swapfile swap swap defaults 0 0

8. Verify that the swap is active by using either the swapon or the free command , as shown below:

   # swapon --show
   # free -h

9. 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 try to avoid swapping whenever possible, while a higher value will make the kernel 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

10. While the swappiness value of 60 is OK for most Linux systems, for production servers, you may need to set a lower value.