Creating a Swap File

Use the dd command to create a file of the required size, for example, one million 1KB blocks.

sudo dd if=/dev/zero of=/swapfile bs=1024 count=1000000

1000000+0 records in
1000000+0 records out
1024000000 bytes (1.0 GB, 977 MiB) copied, 6.10298 s, 168 MB/s

Initialize the file as a swap file.

sudo mkswap /swapfile

mkswap: /swapfile: insecure permissions 0644, fix with: chmod 0600 /swapfile
Setting up swapspace version 1, size = 976.6 MiB (1023995904 bytes)
no label, UUID=43964855-e81f-414c-a61c-370408085ba4

Change the permissions on the file so that it is not world readable.
```
sudo chmod 0600 /swapfile
```
Add an entry to the /etc/fstab file so that the system uses the swap file at system reboots, for example:
```
/swapfile       swap       swap       defaults       0 0
```
Regenerate the mount units and register the new configuration in /etc/fstab.
```
sudo systemctl daemon-reload
```
Activate the swap file.
```
sudo swapon /swapfile
```
(Optional) Test whether the new swap file was successfully created by inspecting the active swap space:
```
cat /proc/swaps
```
```
sudo free -h
```