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SSH Advanced

Advanced SSH configuration for DS01 access.

SSH Config File​

Create ~/.ssh/config on your laptop:

Host ds01
    HostName 10.1.23.20
    User <your-username>@hertie-school.lan
    IdentityFile ~/.ssh/id_ed25519
    ForwardAgent yes

Now connect with:

ssh ds01

Without SSH config, use the full format:

ssh <your-username>@hertie-school.lan@10.1.23.20

Key Management​

Generate Key​

# Recommended: Ed25519
ssh-keygen -t ed25519 -C "your-email@example.com"

# Alternative: RSA
ssh-keygen -t rsa -b 4096 -C "your-email@example.com"

Copy to DS01​

ssh-copy-id ds01
# Without SSH config: ssh-copy-id <your-username>@hertie-school.lan@10.1.23.20

Or manually:

cat ~/.ssh/id_ed25519.pub | ssh ds01 "cat >> ~/.ssh/authorized_keys"

Agent Forwarding​

On your laptop:

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

# Connect with forwarding
ssh -A ds01

This lets you use your local key for Git inside DS01.

Port Forwarding (Tunnels)​

Jupyter​

# Forward port 8888
ssh -L 8888:localhost:8888 ds01
# Without SSH keys: ssh -L 8888:localhost:8888 <your-username>@hertie-school.lan@10.1.23.20

# Access at http://localhost:8888

TensorBoard​

# Forward port 6006
ssh -L 6006:localhost:6006 ds01

# Access at http://localhost:6006

Multiple Ports​

ssh -L 8888:localhost:8888 -L 6006:localhost:6006 ds01

In SSH Config​

Host ds01
    HostName 10.1.23.20
    User <your-username>@hertie-school.lan
    LocalForward 8888 localhost:8888
    LocalForward 6006 localhost:6006

Persistent Connections​

ControlMaster​

Add to ~/.ssh/config:

Host ds01
    HostName 10.1.23.20
    User <your-username>@hertie-school.lan
    ControlMaster auto
    ControlPath ~/.ssh/sockets/%r@%h-%p
    ControlPersist 600

Create socket directory:

mkdir -p ~/.ssh/sockets

First connection is slow, subsequent connections are instant.

Keep Alive​

Host ds01
    ServerAliveInterval 60
    ServerAliveCountMax 3

Prevents disconnection on idle.

Multiplexing (tmux/screen)​

tmux on DS01​

# Create session
tmux new -s work

# Detach: Ctrl+B, D

# List sessions
tmux ls

# Reattach
tmux attach -t work

Disconnect-Safe Workflow​

# Connect
ssh ds01

# Start tmux
tmux new -s training

# Run training
python train.py

# Detach (Ctrl+B, D)

# Disconnect SSH (safe to close laptop)

# Later, reconnect
ssh ds01
tmux attach -t training

SCP and rsync​

Copy Files to DS01​

# Single file
scp local-file.txt ds01:~/workspace/project/

# Directory
scp -r local-dir/ ds01:~/workspace/project/

# rsync (better for large transfers)
rsync -avz local-dir/ ds01:~/workspace/project/

Copy Files from DS01​

scp ds01:~/workspace/project/results.csv .
rsync -avz ds01:~/workspace/project/models/ ./models/

VS Code Remote​

Setup​

  1. Install "Remote - SSH" extension
  2. Open Command Palette (Cmd/Ctrl + Shift + P)
  3. Select "Remote-SSH: Connect to Host"
  4. Enter user@ds01-server or select from config

Config for VS Code​

Host ds01
    HostName 10.1.23.20
    User <your-username>@hertie-school.lan
    ForwardAgent yes

Troubleshooting​

Connection Refused​

# Check SSH is running
ssh -v ds01
# Without SSH config: ssh -v <your-username>@hertie-school.lan@10.1.23.20

Permission Denied​

# Check key permissions
ls -la ~/.ssh/
chmod 600 ~/.ssh/id_ed25519
chmod 644 ~/.ssh/id_ed25519.pub

# Test key
ssh -i ~/.ssh/id_ed25519 ds01

Host Key Changed​

# Remove old key (only if expected)
ssh-keygen -R ds01-server

Slow Connection​

Add to config:

Host ds01
    Compression yes
    TCPKeepAlive yes

Security Best Practices​

  1. Use Ed25519 keys (more secure than RSA)
  2. Use passphrase on keys
  3. Don't share private keys
  4. Use agent forwarding instead of copying keys to server
  5. Keep SSH config in ~/.ssh/ (proper permissions)

See Also​