Set Swap 4GB, Swappiness 10.

do-swap.sh

# Execute
run() {
  # Set Swap 4GB, Swappiness 10.
  # ref : https://www.digitalocean.com/community/tutorials/how-to-add-swap-on-ubuntu-14-04
  # Turn the swapfile off if has any.
  sudo swapoff -a

  # Check current disk usage.
  df -h

  # Create and Enable the Swap File 4GB.
  sudo fallocate -l 4G /swapfile

  # Ensure amount of space was reserved
  ls -lh /swapfile
  ## Expected
  # -rw------- 1 root root 4.0G May 12 13:42 /swapfile

  # set up the swap space
  sudo mkswap /swapfile
  ## Expected
  # Setting up swapspace version 1, size = 4194300 KiB
  # no label, UUID=d005a922-31f2-424a-bfe2-97d2455944e7

  # Activating the swap file.
  sudo swapon /swapfile

  # See swap summary.
  sudo swapon -s
  ## Expected
  # Filename				Type		Size	Used	Priority
  # /swapfile                               file		4194300	0	-1

  # Ensure that the swap is permanent by adding it to the fstab file.
  echo '/swapfile       none    swap    sw      0       0' >> /etc/fstab

  # Free!
  free -m
  ## Expected
  #              total       used       free     shared    buffers     cached
  # Mem:           490        183        306          0         21         93
  # -/+ buffers/cache:         68        421
  # Swap:         4095          0       4095

  # Peeking at append result.
  cat /etc/fstab

  # Swappiness to 10 will cause swap to act as an emergency buffer, preventing out-of-memory crashes. 
  echo 10 | sudo tee /proc/sys/vm/swappiness
  echo vm.swappiness = 10 | sudo tee -a /etc/sysctl.conf

  # Show swappiness.
  cat /proc/sys/vm/swappiness

  # Correct permissions on the swap file
  sudo chown root:root /swapfile
  sudo chmod 0600 /swapfile
}

# Process
PROCESS='setup-swapfile'
echo -e "$(tput setaf 3)[$PROCESS] : Begin$(tput sgr0)"
run
echo -e "$(tput setaf 2)[$PROCESS] : End$(tput sgr0)"