SSH connection basics in Linux CLI - Mini Project: Build & Apply

SSH Connection Basics

📖 Scenario: You are learning how to connect securely to a remote computer using SSH (Secure Shell). This is like making a private phone call to a friend's computer to work on it from your own machine.

🎯 Goal: You will create a simple SSH command to connect to a remote server using a username and IP address.

📋 What You'll Learn

Create a variable called username with the exact value user123.

Create a variable called server_ip with the exact value 192.168.1.10.

Use the variables to build an SSH command string called ssh_command in the format ssh user123@192.168.1.10.

Print the ssh_command to show the full SSH command.

💡 Why This Matters

🌍 Real World

SSH is used daily by system administrators and developers to securely access remote servers and manage them from anywhere.

💼 Career

Knowing how to build and use SSH commands is essential for IT jobs, cloud computing, and remote work setups.

1

Set up username variable

Create a variable called username and set it to the exact string user123.

Linux CLI

# Create the username variable
# Your code here

Hint

Use username="user123" to store the username.

2

Set up server IP variable

Create a variable called server_ip and set it to the exact string 192.168.1.10.

Linux CLI

username="user123"
# Create the server_ip variable
# Your code here

Hint

Use server_ip="192.168.1.10" to store the IP address.

3

Build the SSH command string

Create a variable called ssh_command that combines username and server_ip into the string ssh user123@192.168.1.10 using string interpolation.

Linux CLI

username="user123"
server_ip="192.168.1.10"
# Build the ssh_command string
# Your code here

Hint

Use ssh_command="ssh ${username}@${server_ip}" to build the command.

4

Print the SSH command

Print the variable ssh_command to display the full SSH command.

Linux CLI

username="user123"
server_ip="192.168.1.10"
ssh_command="ssh ${username}@${server_ip}"
# Print the ssh_command
# Your code here

Hint

Use echo "$ssh_command" to print the command.

Practice

1. What does the command ssh user@hostname do?

easy

A. Lists files on the remote computer.

B. Copies files from the remote computer to local.

C. Starts a secure connection to the remote computer as 'user'.

D. Deletes the user account on the remote computer.

Solution

1. Step 1: Understand the ssh command purpose

   The ssh command is used to securely connect to another computer over a network.

2. Step 2: Analyze the syntax ssh user@hostname

   This syntax means connect as 'user' to the computer identified by 'hostname'.

3. Final Answer:

   Starts a secure connection to the remote computer as 'user'. -> Option C

4. Quick Check:

   ssh user@hostname = Secure connection [OK]

Hint: ssh user@host means connect securely as user [OK]

Common Mistakes:

• Thinking ssh copies files instead of connecting
• Confusing ssh with file listing commands
• Assuming ssh deletes accounts

2. Which of these is the correct syntax to connect to a remote server with ssh?

easy

A. ssh user@hostname

B. ssh -connect user hostname

C. ssh connect user@hostname

D. ssh user hostname

Solution

1. Step 1: Recall ssh command syntax

   The correct syntax is ssh user@hostname without extra words or flags for basic connection.

2. Step 2: Check each option

   Options A, B, and D have incorrect syntax or missing '@' sign.

3. Final Answer:

   ssh user@hostname -> Option A

4. Quick Check:

   Correct ssh syntax = ssh user@hostname [OK]

Hint: ssh always uses user@hostname format [OK]

Common Mistakes:

• Adding extra words like 'connect' in command
• Omitting '@' between user and hostname
• Using flags incorrectly for basic ssh

3. What will happen if you run ssh alice@192.168.1.10 and the password is correct?

medium

A. You will see a list of files on your local computer.

B. The remote computer will shut down.

C. Your local files will be deleted.

D. You will be logged into the remote computer as user alice.

Solution

1. Step 1: Understand ssh login process

   Running ssh with user and IP tries to connect and log in to that remote machine.

2. Step 2: Check what happens on correct password

   If password is correct, you get a command prompt on the remote machine as that user.

3. Final Answer:

   You will be logged into the remote computer as user alice. -> Option D

4. Quick Check:

   ssh + correct password = remote login [OK]

Hint: Correct password means remote login success [OK]

Common Mistakes:

• Thinking ssh shuts down remote machine
• Confusing ssh with file deletion
• Assuming ssh lists local files

4. You try to connect with ssh [e-mail] but get the error: Permission denied (publickey). What is the likely problem?

medium

A. You typed the wrong hostname.

B. Your SSH key is missing or not accepted by the server.

C. The server is turned off.

D. You forgot to install ssh on your computer.

Solution

1. Step 1: Understand the error message

   "Permission denied (publickey)" means the server expects an SSH key for authentication but did not accept yours.

2. Step 2: Identify cause of error

   This usually means your SSH key is missing, not loaded, or not authorized on the server.

3. Final Answer:

   Your SSH key is missing or not accepted by the server. -> Option B

4. Quick Check:

   Permission denied (publickey) = SSH key issue [OK]

Hint: Permission denied (publickey) means SSH key problem [OK]

Common Mistakes:

• Assuming hostname typo causes this error
• Thinking server power state causes this error
• Believing ssh must be installed locally to connect

5. You want to connect to a remote server at example.com as user admin but the server uses a non-standard port 2222. Which command will connect correctly?

hard

A. ssh -p 2222 [e-mail]

B. ssh [e-mail]:2222

C. ssh [e-mail] -port 2222

D. ssh [e-mail]

Solution

1. Step 1: Recall how to specify a port in ssh

   The correct flag to specify a port is -p followed by the port number.

2. Step 2: Analyze each option

   ssh -p 2222 [e-mail] uses -p 2222 correctly. Options A, C, and D use incorrect syntax or wrong placement.

3. Final Answer:

   ssh -p 2222 [e-mail] -> Option A

4. Quick Check:

   Use -p to specify port in ssh [OK]

Hint: Use ssh -p port user@host for custom ports [OK]

Common Mistakes:

• Putting port after hostname with colon
• Using -port instead of -p
• Changing hostname to include port number