make 4G swap on CentOS

make-swap.sh

#!/bin/sh
SWAP_SIZE=4G

echo "create $SWAP_SIZE  swap"
# on centos 6
#fallocate -l $SWAP_SIZE /swapfile

# on centos 7
dd if=/dev/zero of=/swapfile count=4096 bs=1MiB

echo "enable swap"
chmod 600 /swapfile
mkswap -f /swapfile
swapon /swapfile
swapon -s
free -h


echo "add swapfile into fstab"
echo "/swapfile   swap    swap    sw  0   0"  >> /etc/fstab



echo "swap setting"

echo "vm.swappiness = 10" >> /etc/sysctl.conf
echo "vm.vfs_cache_pressure = 50" >> /etc/sysctl.conf