(Unix) Store & use credentials for fstab

This is useful when auto-mounting by /etc/fstab is disabled due to the mount requiring login credentials every time.

Create a credentials file under /root AS ROOT using sudoedit, e.g.:
```
sudoedit /root/<CREDENTIALS_FILENAME>`
```
In the editor, write the login credentials for a given mount:
```
username=<MOUNT_USERNAME>
password=<MOUNT_PASSWORD>
```

Confirm that the user of the new file is root:

sudo ls -al /root | grep <CREDENTIALS_FILENAME>

Change permissions of the file so that the file can be read/written only as root:
```
sudo chmod 600 /root/<CREDENTIALS_FILENAME>
```
In /etc/fstab, specify credentials= option under -o flag of the mount of interest:
```
... -o ...,credentials=/root/<CREDENTIALS_FILENAME>,... ...
```
Test that the credentials work:
```
sudo mount -av
```

References:

Written on May 2, 2022