Ubuntu 18.04 enable swap file
check Swap
```
swapon --show
```
Check free memory and disk
```
free -h
// or
df -h
```
```
a) Make swap off
# swapoff /var/swapfile
b) Resize the swapfile (increase or decrease). Here let us increase to 2GB (assuming existing one has 1GB space as given in the article)
# dd if=/dev/zero of=/var/swapfile bs=1024k count=2000
c) Make swapfile usable
# mkswap /var/swapfile
d) Make swapon
# swapon /var/swapfile
d-1) change permission to 0600
# chmod 0600 /var/swapfile
e) Verify the swapfile
# swapon -show
```
Make swap file permanent
```
echo '/var/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
```