ssh

<!-- TOC: Quick Start | THE EXACT PROMPT | Essential Commands | Config | AGENTS.md Blurb | References -->

SSH — Secure Remote Access

Core Capability: Secure shell connections, key management, tunneling, and file transfers.

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Quick Start

# Connect to server
ssh user@hostname

# Connect with specific key
ssh -i ~/.ssh/my_key user@hostname

# Run remote command
ssh user@host "cd /app && git status"

# Copy file to remote
scp local.txt user@host:/remote/path/

# Sync directory (preferred over scp)
rsync -avzP ./local/ user@host:/remote/

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THE EXACT PROMPT — Common Workflows

Connect Through Jump Host

# Single jump (bastion)
ssh -J jumphost user@internal-server

# Multiple jumps
ssh -J jump1,jump2 user@internal-server

Local Port Forward (access remote service locally)

# Access remote:80 via localhost:8080
ssh -L 8080:localhost:80 user@host

# Access db-server:5432 via localhost:5432 through jumphost
ssh -L 5432:db-server:5432 user@jumphost

Generate and Deploy Key

# Generate Ed25519 key (recommended)
ssh-keygen -t ed25519 -C "you@example.com"

# Copy public key to server
ssh-copy-id user@host

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Essential Commands

Task	Command
Connect	ssh user@host
Connect on port	ssh -p 2222 user@host
Connect with key	ssh -i ~/.ssh/key user@host
Run remote command	ssh user@host "command"
Interactive remote	ssh -t user@host "htop"
Copy to remote	scp file.txt user@host:/path/
Copy from remote	scp user@host:/path/file.txt ./
Sync to remote	rsync -avzP ./local/ user@host:/remote/
Local forward	ssh -L local:remote:port user@host
Remote forward	ssh -R remote:local:port user@host
SOCKS proxy	ssh -D 1080 user@host
Jump host	ssh -J bastion user@internal
Generate key	ssh-keygen -t ed25519
Copy key to server	ssh-copy-id user@host
Debug connection	ssh -vvv user@host

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SSH Config

Location: ~/.ssh/config

Host myserver
    HostName 192.168.1.100
    User deploy
    Port 22
    IdentityFile ~/.ssh/myserver_key
    ForwardAgent yes

Host internal
    HostName 10.0.0.50
    User deploy
    ProxyJump bastion

Then connect with just: ssh myserver

Connection Multiplexing (faster reconnects)

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

mkdir -p ~/.ssh/sockets

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SSH Agent

# Start agent
eval "$(ssh-agent -s)"

# Add key
ssh-add ~/.ssh/id_ed25519

# Add with macOS keychain
ssh-add --apple-use-keychain ~/.ssh/id_ed25519

# List loaded keys
ssh-add -l

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Security Tips

• Use Ed25519 keys (faster, more secure than RSA)
• Set PasswordAuthentication no on servers
• Keep keys encrypted with passphrases
• Use ssh-agent to avoid typing passphrase repeatedly
• Restrict key usage with command= in authorized_keys

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AGENTS.md Blurb

Copy this to your project's AGENTS.md:

### SSH Access

SSH is configured for these servers:

- **Production:** `ssh prod` (via ~/.ssh/config)
- **Staging:** `ssh staging`

Common operations:

\`\`\`bash
ssh prod "cd /app && git status"      # Check deploy status
rsync -avzP ./dist/ prod:/app/dist/   # Sync files
ssh -L 5432:localhost:5432 prod       # DB tunnel
\`\`\`

Keys: `~/.ssh/id_ed25519` (add with `ssh-add`)

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References

Topic	Reference
Full command reference	COMMANDS.md
Port forwarding details	TUNNELS.md
Key management	KEYS.md