SSH Key Generator Script

A bash script to streamline the generation of multiple SSH key pairs and automatically update your SSH config file.

Features

• Generates multiple SSH key pairs using Ed25519 algorithm
• Automatically updates ~/.ssh/config with host configuration blocks
• Supports optional passphrases for all generated keys
• Adds keys to SSH agent automatically (if running)
• Handles existing keys gracefully
• User-friendly status messages and warnings

Prerequisites

• Bash shell
• ssh-keygen utility (usually included with OpenSSH)
• ssh-agent running (optional, but recommended for automatic key loading)

Installation

1. Download the script or create a file with the script contents
2. Make it executable:

   chmod +x script_name.sh

Usage

Basic Syntax

./script_name.sh -n <key_name_1> [key_name_2] [...] [-p]

Arguments

• -n (MANDATORY): Signals the start of the list of key names
• <key_name>: One or more names for the keys (e.g., github, server_a)
• -p (OPTIONAL): Prompts for a passphrase to protect all generated keys

Examples

Generate two keys without passphrases:

./script_name.sh -n github_personal prod_eu_access

Generate a single key with a passphrase:

./script_name.sh -n test_server_key -p

Generate multiple keys with passphrases:

./script_name.sh -n github gitlab server_a -p

What the Script Does

1. Parses arguments to collect key names and options
2. Prompts for passphrase (if -p flag is used) with confirmation
3. Creates ~/.ssh directory if it doesn't exist
4. Initializes SSH config file if missing
5. Generates key pairs using Ed25519 algorithm
6. Adds keys to SSH agent automatically (if agent is running)
7. Updates SSH config with new host configuration blocks

SSH Config Updates

The script automatically appends configuration blocks to your ~/.ssh/config file in the following format:

Host <key_name>
    HostName CHANGEME
    User CHANGEME
    IdentityFile ~/.ssh/<key_name>
    PreferredAuthentications publickey
    IdentitiesOnly yes
    AddKeysToAgent yes

Important: You must manually replace CHANGEME values with your actual server hostname and username.

Output Files

Generated keys are created in the current directory:

• <key_name> (private key)
• <key_name>.pub (public key)

It's recommended to move these to ~/.ssh/ after generation.

Checking Your Keys

After running the script, verify your keys are loaded in the SSH agent:

ssh-add -l

SSH Agent Note

If SSH agent is not running, you'll see a warning. To start it, run:

eval $(ssh-agent -s)

Permissions

• .ssh directory: 700 (created automatically)
• .ssh/config file: 600 (created automatically)
• Private keys: 600 (created by ssh-keygen)
• Public keys: 644 (created by ssh-keygen)

Troubleshooting

• Keys not added to agent: Make sure SSH agent is running or check the passphrase
• Config already exists: If a Host entry already exists, the script skips the update to avoid duplicates
• Permission denied: Ensure the script is executable (chmod +x) and you have write permissions in the output directory
• Script won't run: Verify bash is available and the file isn't corrupted (check for proper line endings)