How to add swap to CentOS 7

setup.sh

# Check if we already have swap
swapon -s

# Second Check
free -m

# Check available space
df -h

# Generate the file (4GB)
sudo dd if=/dev/zero of=/swapfile count=4096 bs=1MiB

# Set correct permissions
sudo chmod 600 /swapfile

# Make it swap
sudo mkswap /swapfile

# Turn it on
sudo swapon /swapfile

# Test
swapon -s 
free -m


# To Make Permanent
sudo nano /etc/fstab

# Add the following
/swapfile   swap    swap    sw  0   0


# Check Swappiness (default 30)
cat /proc/sys/vm/swappiness

# To change the level (60 on Mag2 Cluster)
sudo nano /etc/sysctl.conf

# Find the line
vm.swappiness = 60