SSH key generation (ssh-keygen) in Linux CLI - Step-by-Step Execution

Concept Flow - SSH key generation (ssh-keygen)

Start ssh-keygen command

↓

Prompt for file location

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Prompt for passphrase

↓

Generate key pair files

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Show key fingerprint and location

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End

The ssh-keygen command runs, asks where to save the key, asks for a passphrase, then creates the key files and shows their info.

Execution Sample

Linux CLI

ssh-keygen -t rsa -b 2048
# User presses Enter to accept default file
# User enters passphrase or empty
# Key files created

Generates an RSA SSH key pair with 2048 bits, saving to default location, optionally secured by a passphrase.

Execution Table

Step	Action	User Input	System Output	Result
1	Run ssh-keygen command		Generating public/private rsa key pair.	Starts key generation
2	Prompt for file location	Press Enter	Enter file in which to save the key (/home/user/.ssh/id_rsa):	Default path chosen
3	Prompt for passphrase	Enter passphrase or empty	Enter passphrase (empty for no passphrase):	Passphrase recorded or empty
4	Prompt for passphrase confirmation	Repeat passphrase or empty	Enter same passphrase again:	Passphrase confirmed
5	Generate keys		Your identification has been saved in /home/user/.ssh/id_rsa Your public key has been saved in /home/user/.ssh/id_rsa.pub The key fingerprint is: SHA256:abc123... user@host	Key files created
6	Exit			ssh-keygen process ends

💡 Key files created and saved, process ends

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
file_path	none	/home/user/.ssh/id_rsa	/home/user/.ssh/id_rsa	/home/user/.ssh/id_rsa	/home/user/.ssh/id_rsa
passphrase	none	none	user input or empty	confirmed passphrase or empty	stored securely

Key Moments - 2 Insights

Why does ssh-keygen ask twice for the passphrase?

It asks twice to make sure you typed the passphrase correctly, as shown in steps 3 and 4 in the execution table.

What happens if I just press Enter at the file location prompt?

Pressing Enter chooses the default file path for the key, as shown in step 2 where the default /home/user/.ssh/id_rsa is selected.

Visual Quiz - 3 Questions

Look at the execution table, what is the file path chosen after step 2?

A /root/.ssh/id_rsa

B /etc/ssh/id_rsa

C /home/user/.ssh/id_rsa

D No file chosen yet

💡 Hint

Check the 'User Input' and 'Result' columns in step 2 of the execution table.

At which step does ssh-keygen confirm the passphrase?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look for the step where the system asks to 'Enter same passphrase again' in the execution table.

If you enter a passphrase at step 3, what happens at step 5?

A ssh-keygen asks for passphrase again

B Key files are created and passphrase protects the private key

C Key files are created without passphrase protection

D ssh-keygen exits without creating keys

💡 Hint

Refer to the 'Result' column at step 5 and the 'passphrase' variable in variable_tracker.

Concept Snapshot

ssh-keygen -t rsa -b 2048
- Runs key generation
- Prompts for file location (default if Enter)
- Prompts twice for passphrase
- Creates private and public key files
- Shows key fingerprint and location

Full Transcript

The ssh-keygen command starts and asks where to save the SSH key. If you press Enter, it uses the default location. Then it asks for a passphrase twice to confirm it. After that, it creates the private and public key files and shows their fingerprint and location. The process ends after keys are created. Variables like file path and passphrase change as you provide input. This helps secure your SSH connections.