vastai-install-auth

What this skill does

# Vast.ai Install & Auth

## Overview

Set up the Vast.ai CLI and REST API access for renting GPU compute instances. Vast.ai is a marketplace where individual hosts and data centers list GPU machines at prices significantly below hyperscaler providers.

## Prerequisites

- Python 3.8+
- Vast.ai account at https://cloud.vast.ai
- Credit card or credits loaded for GPU rental

## Instructions

### Step 1: Install the CLI

```bash
set -euo pipefail
pip install vastai
vastai --version
```

### Step 2: Get Your API Key

1. Log in at https://cloud.vast.ai
2. Navigate to **Account** > **API Keys** (or visit https://cloud.vast.ai/cli/)
3. Copy your API key (a long hexadecimal string)

### Step 3: Configure Authentication

```bash
# Save API key to ~/.vast_api_key
vastai set api-key YOUR_API_KEY_HERE

# Verify authentication
vastai show user
```

For programmatic use, set the environment variable:

```bash
export VASTAI_API_KEY="your-api-key-here"
echo 'VASTAI_API_KEY=your-api-key' >> .env
```

### Step 4: Verify with REST API

```bash
# Direct REST API call — base URL is cloud.vast.ai/api/v0
curl -s -H "Authorization: Bearer $VASTAI_API_KEY" \
  "https://cloud.vast.ai/api/v0/users/current" | jq '{id, username, balance}'
```

### Step 5: Python Client Setup

```python
# vastai_client.py
import os
import requests
from typing import Optional, Dict, Any, List

class VastClient:
    BASE_URL = "https://cloud.vast.ai/api/v0"

    def __init__(self, api_key: Optional[str] = None):
        self.api_key = api_key or os.environ.get("VASTAI_API_KEY")
        if not self.api_key:
            # Fall back to ~/.vast_api_key
            key_file = os.path.expanduser("~/.vast_api_key")
            if os.path.exists(key_file):
                self.api_key = open(key_file).read().strip()
        if not self.api_key:
            raise ValueError("No API key found. Run: vastai set api-key YOUR_KEY")

        self.session = requests.Session()
        self.session.headers.update({
            "Authorization": f"Bearer {self.api_key}",
            "Accept": "application/json",
        })

    def _request(self, method: str, endpoint: str, **kwargs) -> Dict[str, Any]:
        url = f"{self.BASE_URL}{endpoint}"
        resp = self.session.request(method, url, **kwargs)
        resp.raise_for_status()
        return resp.json()

    def search_offers(self, query: Dict[str, Any]) -> List[Dict]:
        return self._request("GET", "/bundles/", params={"q": str(query)})

    def create_instance(self, offer_id: int, image: str, disk_gb: float = 20,
                        onstart: str = "", env: Dict = None) -> Dict:
        body = {"client_id": "me", "image": image, "disk": disk_gb,
                "onstart": onstart, "env": env or {}}
        return self._request("PUT", f"/asks/{offer_id}/", json=body)

    def show_instances(self) -> List[Dict]:
        return self._request("GET", "/instances/")["instances"]

    def destroy_instance(self, instance_id: int) -> Dict:
        return self._request("DELETE", f"/instances/{instance_id}/")

# Quick verification
if __name__ == "__main__":
    client = VastClient()
    user = client._request("GET", "/users/current")
    print(f"Authenticated as: {user['username']}")
    print(f"Balance: ${user.get('balance', 0):.2f}")
```

### Step 6: Verify Connection

```bash
# CLI verification
vastai show user
vastai search offers 'num_gpus=1 gpu_name=RTX_4090' --limit 3

# Python verification
python vastai_client.py
```

## Output

- `vastai` CLI installed and authenticated
- API key saved to `~/.vast_api_key` and/or environment variable
- Python client wrapper with search, create, show, destroy methods
- Successful authentication verification

## Error Handling

| Error | Cause | Solution |
|-------|-------|----------|
| `Invalid API key` | Wrong or expired key | Regenerate at cloud.vast.ai/cli/ |
| `403 Forbidden` | Insufficient balance | Add credits at cloud.vast.ai |
| `Connection refused` | Firewall blocking HTTPS | Allow outbound 443 to cloud.vast.ai |
| `Module not found: vastai` | pip install failed | Run `pip install --upgrade vastai` |
| `~/.vast_api_key not found` | CLI not configured | Run `vastai set api-key YOUR_KEY` |

## Resources

- [Vast.ai CLI Documentation](https://docs.vast.ai/cli/get-started)
- [REST API Reference](https://vast.ai/developers/api)
- [API Introduction](https://docs.vast.ai/api-reference/introduction)
- [GitHub: vast-cli](https://github.com/vast-ai/vast-cli)

## Next Steps

After successful auth, proceed to `vastai-hello-world` for your first GPU instance rental.

## Examples

**Quick CLI test**: Run `vastai search offers 'reliability > 0.99 num_gpus=1' --order 'dph_total'` to find the cheapest reliable single-GPU offers. Verify your key works before writing any code.

**REST API test**: Use curl with your Bearer token to hit `cloud.vast.ai/api/v0/users/current` and confirm your username and balance are returned correctly.