Boyang Yan

Permanently Disable Swap Partition

3 min read

what is Swap

How to Check Swap Space in Linux

Before actually disabling swap space, first, you need to visualize your memory load degree and then identify the partition that holds the swap area, by issuing the below free command.

boyang@k8s-worker2:~$ free -h
               total        used        free      shared  buff/cache   available
Mem:           3.8Gi       193Mi       3.3Gi       0.0Ki       340Mi       3.4Gi
Swap:          3.0Gi          0B       3.0Gi

Look for the Swap space used size. If the used size is 0B or close to 0 bytes, it can be assumed that swap space is not used intensively and can be safely disabled.

How to Disable Swap in Linux

After you’ve identified the swap partition or file, execute the below command to deactivate the swap area.

sudo swapoff -a

Run free command in order to check if the swap area has been disabled.

boyang@k8s-worker2:~$ free -h
               total        used        free      shared  buff/cache   available
Mem:           3.8Gi       190Mi       3.3Gi       0.0Ki       342Mi       3.4Gi
Swap:             0B          0B          0B

How to Disable Swap Permanently in Linux

In order to permanently disable swap space in Linux, open /etc/fstab file, search for the swap line and comment on the entire line by adding a # (hashtag) sign in front of the line, as shown in the below.

vi /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to nam
e devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <
pass>
# / was on /dev/ubuntu-vg/ubuntu-lv during curtin installation
/dev/disk/by-id/dm-uuid-LVM-oqXcZ9SBcGRIYBMm921eX1ifQSqU4LnDm5YhM
NjdAmLFAYKSU9XfhHl96Q2P2ywd / ext4 defaults 0 1
# /boot was on /dev/sda2 during curtin installation
/dev/disk/by-uuid/72af1baa-fd38-42a3-a6ea-5b894da6d38b /boot ext4
 defaults 0 1
/swap.img       none    swap    sw      0       0

Afterward, reboot the system in order to apply the new swap setting or issue mount -a command in some cases might do the trick.

mount -a

Auto Script

#!/bin/bash
 
# Function to comment out lines containing the keyword
comment_lines_with_keyword() {
    local keyword=$1
    local file=$2
 
    # Create a temporary file
    local temp_file=$(mktemp)
 
    while IFS= read -r line; do
        if [[ $line == *"$keyword"* ]]; then
            echo "# $line" >> "$temp_file"
        else
            echo "$line" >> "$temp_file"
        fi
    done < "$file"
    # Make file backup
    sudo mv "$file" "$file.backup"
    # Overwrite the original file with the modified content
    sudo mv "$temp_file" "$file"
    echo "Modified content written back to $file"
}
 
# check swap size, if swap great than 1 bytes, disable Swap permanently
disable_swap_permanently() {
    # Get swap size in bytes
    swap_size=$(grep 'SwapTotal' /proc/meminfo | awk '{print $2}')
 
    # Check if the variable is less than 1
    if (( $(echo "$swap_size < 1" | bc -l) )); then
        echo "The Swap size is less than 1 bytes."
    else
        echo "The variable is not less than 1."
        # Print the swap size
        echo "Swap Size: $swap_size"
        # disable swap permanently
        comment_lines_with_keyword "swap" "/etc/fstab"
    fi
 
}
 
echo "K8S required Disable Swap"
read -p "Do you want to Disable Swap Permanently? Otherwise Disable Temporarily (yes/no): " answer
 
case "$answer" in
    [Yy][Ee][Ss]|[Yy])
        echo "Disable Swap Permanently"
        disable_swap_permanently
        # apply the new swap setting
        mount -a
        ;;
    [Nn][Oo]|[Nn])
        echo "Disable Swap Temporarily"
        sudo swapoff -a
        ;;
    *)
        echo "Invalid input. Please enter 'yes' or 'no'."
        ;;
esac

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