Linux Swap and Swapfile
Add/Remove Swapfile Short Guide
Swap On
sudo fallocate -l 4G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
sudo nano /etc/fstab
/swapfile swap swap defaults 0 0
Swap Off
sudo swapoff -a # sudo swapoff /swapfile
sudo rm -f /swapfile
sudo nano /etc/fstab
#/swapfile swap swap defaults 0 0
Check the swap and its usage
sudo swapon --show
sudo free -h
Swap On/Off Scripts
swap-on.sh
#!/bin/bash
sudo fallocate -l 4G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
sudo sed 's_^#/swapfile_/swapfile_' /etc/fstab -i
echo
sudo swapon --show
echo
sudo free -h
swap-off.sh
#!/bin/bash
sudo swapoff /swapfile
sudo rm -f /swapfile
sudo sed 's_^/swapfile_#/swapfile_' /etc/fstab -i
echo
sudo swapon --show
echo
sudo free -h
Adjusting 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 Desktops, for production servers you may need to set a lower value. For example, to set the swappiness value to 10, type:
sudo sysctl vm.swappiness=10
To make this parameter persistent across reboots append the following line to the /etc/sysctl.conf file:
sudo nano /etc/sysctl.conf
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.
References
