If you wish to make the process of attaching an external drive (through cifs) permanent (persistent), then you will need to begin by installing the autofs package in the following way:

# yum install autofs

Having installed the package, you will then need to ensure that you start and enable the autofs service like this:

# systemctl start autofs
# systemctl enable autofs

Having done this, and assuming we will be using the same mount point as discussed here, you should begin the configuration of the autofs service by creating a credentials file in your favorite text editor by typing this:

# nano /path/to/credentials.txt

Now, add the required network credentials like this:

username=<access_username>
password=<access_password>

Having saved and closed this file, make sure that the permissions are modified to ensure system security:

# chmod 600 /path/to/credentials.txt

The next stage of this process is to open the autofs configuration file:

# nano...