1. Enable Swap

1.1 Check the usage of Swap

               total        used        free      shared  buff/cache   available
Mem:             417         188          21           2         221         229
Swap:           2047           0        2047

1.2 Add Swap file

cd /usr
mkdir swap && cd swap
dd if=/dev/zero of=/usr/swap/swapfile1 bs=1M count=2048

bs=1M means the size of block written is 1M，count=2048 means we created a swap file which is 2048M totally.

1.3 Check the size of swap file created

du -sh /usr/swap/swapfile1

1.4 Make the swap file to be recognized by system

mkswap /usr/swap/swapfile1

1.5 Enable usage of the swap file

swapon /usr/swap/swapfile1

1.6 Edit /etc/fstab

/usr/swap/swapfile1 swap swap defaults 0 0

1.7 Check the swap file mounted successfully

swapon -s

Reference:
[1]:https://timberkito.com/?p=98