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How to enable SWAP on your server

Donell Cox
  • Updated

Introduction

This article outlines how you can enable SWAP on your server. The below examples assume you are using CentOS or another RedHat RHEL-based operating system.

cPanel support can not assist or support enabling SWAP on your server. The procedure below is intended to serve as a guide and involves editing sensitive files that are part of your file system configuration. If you are uncomfortable making the changes, we recommend contacting a qualified System Administrator for detailed assistance.

 

Procedure 

For CentOS, AlmaLinux, and RockyLinux:

  1. Determine if SWAP is enabled on the server already. The output from the following command can tell you. If SWAP is not enabled, the following command will produce no output:

    root@server [~] # swapon -s
    [No Output]
  2. If SWAP is already enabled and you are trying to resize the partition, follow the instructions in this companion article instead:
    How to resize SWAP on your server
  3. If SWAP is not enabled, we can set it up start to set it up by creating a disk image. We will use an example path for the SWAP disk image. The following is an example of setting up such an image using the 'dd' tool: 
    dd if=/dev/zero of=/root/cp-swap bs=1M count=2000
  4. Set permissions on the disk image: 
    chmod 0600 /root/cp-swap
  5. Verify that the image was created and has the proper permissions: 
    root@server [~] # ls -al /root/cp-swap
    -rw------- 1 root root 2097152000 Jan 1 00:00 /root/cp-swap
  6. Before we can use it, we must format the disk image to be useable as SWAP: 
    mkswap /root/cp-swap
  7. Now we can enable SWAP using the disk image we created: 
    swapon /root/cp-swap
  8. We can use the command from Step 1 to verify SWAP is enabled now: 
    root@server [~] # swapon -s
    Filename Type Size Used Priority
    /root/cp-swap file 2047996 0 -3
  9. To make the change permanent, you will need to add the following entry to your server's /etc/fstab file. Please use extreme caution when modifying the /etc/fstab file. It is responsible for the mounting of the partitions on the server. If you are unfamiliar with the file, we would recommend having a qualified System Administrator make the change:
     
    /root/cp-swap swap swap defaults 0 0

 

Resources

How to check available swap space on your server.

 

 

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