Code Anywhere: Setting Up Claude Code on a VPS with Mobile Access¶

Ever seen someone coding at a cafe from their phone and wondered how? Here's the exact setup to run Claude Code (and OpenAI Codex) on a remote server and access it from your phone, tablet, or any device with an internet connection.

Inspired by levelsio's tweet about coding on his phone via Termius + Claude Code while out and about.

What You'll Need¶

• A DigitalOcean account (or any VPS provider — Hetzner, Vultr, etc.)
• A phone with Termius installed (iOS/Android)
• 10 minutes

Step 1: Generate an SSH Key¶

On your local machine (Mac/Linux):

ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519_claude_vps

It'll ask for a passphrase — set one for security or leave empty for convenience.

This creates two files: - ~/.ssh/id_ed25519_claude_vps — your private key (never share this) - ~/.ssh/id_ed25519_claude_vps.pub — your public key (this goes on the server)

Copy the public key to your clipboard:

# macOS
cat ~/.ssh/id_ed25519_claude_vps.pub | pbcopy

# Linux
cat ~/.ssh/id_ed25519_claude_vps.pub | xclip -selection clipboard

Gotcha: The public key starts with ssh-ed25519 AAAA.... The private key starts with -----BEGIN OPENSSH PRIVATE KEY-----. Know the difference — you'll need both at different steps.

Step 2: Create a DigitalOcean Droplet¶

1. Go to cloud.digitalocean.com → Create → Droplets
2. Region: Pick the closest to you (lower latency = snappier terminal)
3. Image: Ubuntu 24.04 LTS
4. Size: Basic → Regular → $6/mo (1 vCPU, 1GB RAM)
5. Authentication: Select SSH Key → paste your public key (the one you copied with pbcopy)
6. Hostname: claude-dev (or whatever you like)
7. Hit Create Droplet

Note down the IP address once it's ready (e.g., 134.209.42.100).

Why not AWS? A simple VPS has predictable billing ($6/mo flat), no surprise charges, and zero config overhead. AWS EC2 makes sense if you're already in that ecosystem, but for "SSH in and code" it's overkill.

Step 3: Set Up SSH Config (Saves Time Later)¶

Add this to ~/.ssh/config on your local machine:

Host claude-dev
    HostName <your-droplet-ip>
    User root
    IdentityFile ~/.ssh/id_ed25519_claude_vps

Note: We're using root for now to set up the server. You'll change this to a non-root user in Step 5.

Now you can connect with just:

ssh claude-dev

Gotcha: If you get UNPROTECTED PRIVATE KEY FILE error, fix permissions:

chmod 600 ~/.ssh/id_ed25519_claude_vps

SSH refuses to use a private key that other users can read.

Gotcha: Use the private key (without .pub) in your SSH command and config. The .pub file is only for pasting into servers/services. If you use the .pub file with ssh -i, you'll get a Permission denied error.

Step 4: Install Everything on the Server¶

SSH into your droplet and run this setup script:

ssh claude-dev

Then paste:

#!/bin/bash
set -e

# Install Node.js 22
curl -fsSL https://deb.nodesource.com/setup_22.x | sudo bash -
sudo apt install -y nodejs

# Install Claude Code
sudo npm install -g @anthropic-ai/claude-code

# Install OpenAI Codex (optional)
sudo npm install -g @openai/codex

# Install tmux for persistent sessions
sudo apt install -y tmux

echo "Done! Run: tmux new -s claude && claude"

Or save it as a script and SCP it over:

scp -i ~/.ssh/id_ed25519_claude_vps setup.sh root@<your-ip>:~
ssh claude-dev "bash ~/setup.sh"

Step 5: Create a Non-Root User¶

Claude Code refuses to run as root for security reasons. You need to create a regular user:

ssh claude-dev

# Create a new user called "claude" with no password prompt
adduser claude --disabled-password --gecos ""

# Give the user sudo privileges (for installing packages later)
usermod -aG sudo claude

# Copy root's SSH keys so you can SSH in as this new user
cp -r ~/.ssh /home/claude/.ssh

# Fix ownership — copied files are owned by root, change to claude
chown -R claude:claude /home/claude/.ssh

Now update your local ~/.ssh/config to use the new user:

Host claude-dev
    HostName <your-droplet-ip>
    User claude
    IdentityFile ~/.ssh/id_ed25519_claude_vps

Test it:

ssh claude-dev

You should now be logged in as claude instead of root.

Gotcha: If you skip this step and try to run Claude Code as root, you'll get: --dangerously-skip-permissions cannot be used with root/sudo privileges for security reasons. Don't try to force it — just create a regular user.

Step 6: Add Swap (Prevent Crashes on 1GB Droplet)¶

The $6 droplet only has 1GB RAM. Adding swap prevents out-of-memory crashes:

ssh claude-dev "sudo fallocate -l 2G /swapfile && sudo chmod 600 /swapfile && sudo mkswap /swapfile && sudo swapon /swapfile && echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab"

This gives you 2GB of virtual memory. Not as fast as real RAM but keeps things stable.

Step 7: Start Coding with tmux¶

tmux keeps your session alive even when you disconnect (phone loses signal, close the app, etc.).

ssh claude-dev

# First time: create a session
tmux new -s claude

# Run Claude Code
claude

When you disconnect and come back:

ssh claude-dev
tmux attach -t claude

Your session is exactly where you left it.

tmux essentials: | Action | Keys | |---|---| | Detach (leave session running) | Ctrl+B then D | | Reattach | tmux attach -t claude | | New window | Ctrl+B then C | | Switch windows | Ctrl+B then 0-9 | | Scroll up | Ctrl+B then [ (press q to exit scroll) |

Step 8: Set Up Termius on Your Phone (Code From Anywhere)¶

1. Download Termius from App Store / Play Store
2. Go to Keychain → Keys → tap + → Import
3. Paste your private key (the one starting with -----BEGIN OPENSSH PRIVATE KEY-----)

To get it on your phone, on your Mac run:

cat ~/.ssh/id_ed25519_claude_vps

Gotcha: Do NOT paste the public key here. Termius needs the private key. If you see ssh-ed25519 AAAA... that's the wrong one. You need -----BEGIN OPENSSH PRIVATE KEY-----.

1. Go to Hosts → tap +:
2. Label: claude-dev
3. Hostname: <your-droplet-ip>
4. Username: claude
5. Key: Select the key you just imported
6. Save → tap the host to connect
7. Run tmux attach -t claude to pick up where you left off

Security Tips¶

• Never share your private key. If you emailed it to yourself to get it on your phone, delete that email.
• Disable password auth on your server (it's off by default on DigitalOcean if you chose SSH key auth).
• Consider Tailscale if you want to avoid exposing SSH to the public internet. It creates a private network between your devices.
• Consider Mosh instead of SSH for mobile — it handles flaky connections and network switches (Wi-Fi to 5G) much better than SSH.

Cost¶

That's it. You now have a cloud dev environment accessible from any device. Start a tmux session, fire up Claude Code, and code from anywhere.