Creating a swapfile suitable for Oracle XE on CentOS

centos_swapfile.sh

# Oracle XE requires a swap file of at least twice the size of physical memory
# see https://www.digitalocean.com/community/tutorials/how-to-add-swap-on-centos-6

# check current swap file
swapon -s
# check available space
df

# setup 2GB swap file
dd if=/dev/zero of=/swapfile bs=1024 count=2048k
mkswap /swapfile
swapon /swapfile

# check swap file again
swapon -s

# make the swap file permanent
# see http://blog.allanglesit.com/2012/05/bash-programmatically-add-entries-in-fstab/
echo "/swapfile swap swap defaults 0 0" >> /etc/fstab

# prevent file from being world-readable
chown root:root /swapfile 
chmod 0600 /swapfile