Create swap file on linux

# From https://xiaoxing.us/2018/09/04/creating_swap_on_lightsail/

# fallocate is instant; no point wasting time writing zeroes
sudo fallocate -l 8G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
sudo cp /etc/fstab /etc/fstab.bak
# Activate swap on boot
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
# Make system use swap only when it needs it
sudo sysctl vm.swappiness=10
echo 'vm.swappiness=10' | sudo tee -a /etc/sysctl.conf
sudo sysctl vm.vfs_cache_pressure=50
echo 'vm.vfs_cache_pressure=50' | sudo tee -a /etc/sysctl.conf