How to create and use a Swap file (no replies)

This instruction will be revised to add more detailed discussion.

1. Create the swap file of 512MB at the rootfs top directory

cd /
dd if=/dev/zero of=swapfile1 bs=1024 count=524288
mkswap swapfile1 
chmod 0600 swapfile1

2. Turn on swap

swapon /swapfile1

3. Check the swap space

free -h

total        used        free      shared  buff/cache   available
.....
Swap:          511Mi          0B       511Mi

swapon

NAME       TYPE SIZE USED PRIO
/swapfile1 file 512M   0B   -2

4. Add swapfile1 entry to fstab so that it will be automatically on during boot.

cat /etc/fstab

# /etc/fstab: static file system information.
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
LABEL=rootfs   /               ext3    noatime,user_xattr,acl,errors=remount-ro 0 1
/swapfile1     swap            swap    defaults          0       0
tmpfs          /tmp            tmpfs   defaults          0       0