SSH Explained Through Questions

In this article, I'm sharing some frequently asked questions and my answers regarding SSH. If you also have SSH-related "how-to" questions, feel free to leave a comment below.

QUESTION 1: What is SSH? ANSWER 1: SSH stands for Secure Shell, and it's a protocol used to securely access remote servers. It is widely used for remote administration and secure data transmission between two hosts by encrypting the communication.

QUESTION 2: What is the default port of the SSH protocol? ANSWER 2: By default, SSH uses port 22.

QUESTION 3: Where is the configuration file for the SSH server located? ANSWER 3: The configuration file for the SSH server is located at /etc/ssh/sshd_config.

QUESTION 4: Is it possible to change the default SSH port? ANSWER 4: Yes, it is. Everyone knows the default SSH port is 22. For security reasons, it's a good idea to change it to another available port.

How to do it? STEP 1: Login to the server as root.
STEP 2: Open the SSH config file:

# nano /etc/ssh/sshd_config

STEP 3: Search for the word Port (Use CTRL+W to search). You’ll see something like:

#Port 22

STEP 4: Remove the # at the beginning and change 22 to your desired port (for example, 3214 — just don’t forget it!).
STEP 5: Save the file (CTRL+X).
STEP 6: Restart the SSH service:

# service sshd restart

QUESTION 5: Can we disable direct root login to the server? How? ANSWER 5: Yes, you can disable root login. But first, make sure you have another user created. After login with the user, you can switch to root using su root. Important: If you disable root login without creating another user first, you won’t be able to access your server again!

Open the SSH config with the following command:

# nano /etc/ssh/sshd_config

Search for the line:

PermitRootLogin

Change its value from yes to no. After saving the file, restart the SSH service. Root login will now be disabled.

QUESTION 6: I see welcome messages when logging into some servers via SSH. How are those added? ANSWER 6: This is called a "banner". Adding it is very simple. STEP 1: Create a banner file:

# nano /root/banner.txt

Write the message you want and save the file.

STEP 2: Add the banner to the SSH config:

# nano /etc/ssh/sshd_config

Search for the Banner line, add the path to your banner file, and make sure the line is not commented (remove the # if present).

Banner /root/banner.txt

STEP 3: Restart the SSH service:

# service sshd restart

If you have more questions, feel free to drop them in the comments. I’ll be happy to help.

Good luck!