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Sam Newby
Sam Newby

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Simplify Your Server Connections with SSH Config

#ssh #linux #servers

If you're managing multiple servers, typing out full SSH commands with usernames, IP addresses, and specific keys can become tedious. Let's explore how to use SSH config to make your server connections simpler and more efficient.

Understanding SSH Config

The SSH config file lets you create shortcuts for your SSH connections. Instead of typing:

ssh -i ~/.ssh/staging_key username@203.0.113.1 -p 2222
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You can simply type:

ssh staging
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Setting Up Your SSH Config

  1. Create or open your SSH config file: 
nano ~/.ssh/config
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  1. Set the file permissions (if it's a new file): 
chmod 600 ~/.ssh/config
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Basic Configuration Examples

Here's a simple configuration for a single server:

Host webserver HostName 203.0.113.1 User admin Port 22 IdentityFile ~/.ssh/id_rsa
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Now you can connect by simply typing:

ssh webserver
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Advanced Configuration Examples

Multiple Servers with Different Settings 

# Production Server Host prod HostName 203.0.113.1 User produser Port 22 IdentityFile ~/.ssh/prod_key # Staging Server Host staging HostName 203.0.113.2 User stageuser Port 2222 IdentityFile ~/.ssh/staging_key # Development Server Host dev HostName 203.0.113.3 User devuser IdentityFile ~/.ssh/dev_key
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Using Wildcards

Connect to multiple servers with similar patterns:

# All development servers Host dev-* User developer IdentityFile ~/.ssh/dev_key Port 22 # Matches dev-01, dev-02, etc. Host dev-01 HostName 203.0.113.11 Host dev-02 HostName 203.0.113.12
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Useful SSH Config Options

Connection Settings 

Host myserver HostName 203.0.113.1 User admin Port 22 IdentityFile ~/.ssh/custom_key AddKeysToAgent yes ForwardAgent yes Compression yes
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Keeping Connections Alive 

Host * ServerAliveInterval 60 ServerAliveCountMax 5 TCPKeepAlive yes
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Jump Hosts (Bastion Servers) 

Host private-server HostName 10.0.0.5 User admin ProxyJump bastion IdentityFile ~/.ssh/private_key Host bastion HostName 203.0.113.1 User jumpuser IdentityFile ~/.ssh/bastion_key
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Best Practices

  1. Organization

    • Group related hosts together
    • Use comments to document configurations
    • Keep sensitive production configs separate

  2. Security

    • Use specific IdentityFile for each server
    • Avoid using passwords when possible
    • Set proper file permissions (600)

  3. Default Settings

Host * UseKeychain yes AddKeysToAgent yes IdentitiesOnly yes HashKnownHosts yes
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Practical Use Cases

Development Environment 

# Local Development VMs Host dev-vm HostName localhost User developer Port 2222 StrictHostKeyChecking no # GitHub Host github.com HostName github.com User git IdentityFile ~/.ssh/github_key AddKeysToAgent yes
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Cloud Servers 

# AWS Servers Host aws-* User ec2-user IdentityFile ~/.ssh/aws_key # Digital Ocean Droplets Host do-* User root IdentityFile ~/.ssh/do_key
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Troubleshooting Tips

  1. Connection Issues

    • Use -v flag for verbose output: 
     ssh -v myserver
  • Check file permissions
  • Verify IdentityFile paths
  1. Config File Not Working
    • Ensure correct file permissions (600)
    • Check syntax and indentation
    • Verify file location (~/.ssh/config)

Advanced Features

Multiplexing Connections 

Host * ControlMaster auto ControlPath ~/.ssh/sockets/%r@%h-%p ControlPersist 600
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Different Keys for Different Ports 

Match host * port 2222 IdentityFile ~/.ssh/special_key
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Conclusion

A well-organized SSH config file can significantly streamline your server management workflow. Start with basic configurations and gradually add more advanced features as needed.

Remember to keep your SSH keys secure and regularly update your configurations to reflect your current server infrastructure.

Need help optimizing your server connections? Feel free to reach out to our support team.

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