oam/knowledge base/swap.md

Swap

TL;DR

# show the swap usage
swapon --show
free -h

# enable or disable a swap partition or file
sudo swapon /root/swapfile
sudo swapoff LABEL=swap
sudo swapoff /dev/sda2

# enable or disable *all* swap partition or file
sudo swapon -a
sudo swapoff --all

# chech what processes are swapping
# see the "si" (swap in) and "so" (swap out) columns
vmstat
vmstat --wide 1

Swappiness

# change the current value
sudo sysctl vm.swappiness=10
sudo sysctl -w vm/swappiness=5

# persistent configuration
echo 'vm.swappiness=10'  | sudo tee -a /etc/sysctl.conf
echo 'vm.swappiness = 5' | sudo tee -a /etc/sysctl.d/99-swappiness.conf

Swapfile

# add a swapfile
sudo fallocate -l 1G /swapfile   # or sudo dd if=/dev/zero of=/swapfile bs=1024 count=1048576
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
echo '/swapfile swap swap defaults 0 0' | sudo tee -a /etc/fstab

# remove a swapfile
sudo swapoff -v /swapfile
sudo sed -i.bak '/\/swapfile/d' /etc/fstab
sudo rm /swapfile

Further readings

• create a linux swap file
• How to reload sysctl.conf variables on Linux
• How to empty swap if there is free RAM