SSH Persistent Connection

Automates SSH key-based authentication setup and optimizes connection reliability. Automatically detects and fixes common SSH issues.

When to use

• First time connecting to a new server
• SSH keeps asking for password
• Connections frequently drop or timeout
• Getting locked out by fail2ban

Auto-Setup Flow

When this skill is triggered, Claude should automatically handle the entire process:

Step 1: Check/Generate SSH Key

# Check existing key
if [ -f ~/.ssh/id_ed25519.pub ]; then
    echo "Key exists"
    cat ~/.ssh/id_ed25519.pub
else
    ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519 -N "" -C "$(whoami)@$(hostname)"
fi

Step 2: Deploy Key to Server (with auto-fix)

# Try standard method first
ssh-copy-id -i ~/.ssh/id_ed25519.pub user@server 2>&1

# If that fails, try manual method
cat ~/.ssh/id_ed25519.pub | ssh user@server "cat >> ~/.ssh/authorized_keys" 2>&1

Auto-Fix: Permission Denied on authorized_keys

# Check file attributes
ssh user@server "lsattr ~/.ssh/authorized_keys 2>/dev/null"
# If immutable flag (i) is set:
ssh user@server "echo 'PASSWORD' | sudo -S chattr -i ~/.ssh/authorized_keys"
# Write key
PUB=$(cat ~/.ssh/id_ed25519.pub)
ssh user@server "echo '$PUB' >> ~/.ssh/authorized_keys"
# Restore immutable
ssh user@server "echo 'PASSWORD' | sudo -S chattr +i ~/.ssh/authorized_keys"

Auto-Fix: Wrong Owner on .ssh Directory

# Check ownership
ssh user@server "ls -la ~/.ssh/"
# If owned by different user:
ssh user@server "echo 'PASSWORD' | sudo -S chown user:user ~/.ssh ~/.ssh/authorized_keys"

Auto-Fix: Wrong Permissions

ssh user@server "chmod 700 ~/.ssh; chmod 600 ~/.ssh/authorized_keys"

Step 3: Configure SSH Config

# Check if host already configured
grep -q "Host ALIAS" ~/.ssh/config 2>/dev/null

# Add or update config
cat >> ~/.ssh/config << EOF
Host ALIAS
    HostName SERVER_IP
    User USERNAME
    IdentityFile ~/.ssh/id_ed25519
    ServerAliveInterval 15
    ServerAliveCountMax 20
    ConnectTimeout 30
    TCPKeepAlive yes
EOF

Step 4: Verify

# Test passwordless connection
ssh ALIAS "echo 'Key auth OK'; hostname"

# Measure speed
time ssh ALIAS "echo connected"

Auto-Fix: fail2ban Lockout

If previous password attempts triggered fail2ban:

# Wait 30-60 minutes for auto-unban
# Or if you have sudo on the server via another path:
ssh other-user@server "sudo fail2ban-client set sshd unbanip YOUR_IP"

After fixing, key-based auth prevents future lockouts (no failed password attempts).

Configuration Reference

Host <alias>
    HostName <ip>              # Server IP or domain
    User <username>            # SSH username
    Port <port>                # Default: 22
    IdentityFile <key>         # Private key path
    ServerAliveInterval 15     # Keepalive interval (seconds)
    ServerAliveCountMax 20     # Max missed keepalives
    ConnectTimeout 30          # Connection timeout
    TCPKeepAlive yes           # TCP keepalive

    # Linux/macOS only:
    ControlMaster auto
    ControlPath ~/.ssh/cm-%r@%h:%p
    ControlPersist 4h

Platform Notes