> ## Documentation Index
> Fetch the complete documentation index at: https://docs.microsandbox.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Configuration

> Select a backend and configure the local runtime with the Ruby SDK.

See [Runtime setup](/sdk/setup) and [Cloud](/cloud/overview) for setup examples.

## Microsandbox

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">version</span>

```ruby theme={null}
Microsandbox.version # => String
```

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">String</span></div>
    <div className="msb-param-desc">SDK version.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">installed?</span>

```ruby theme={null}
Microsandbox.installed? # => Boolean
```

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">Boolean</span></div>
    <div className="msb-param-desc">Whether a complete local runtime installation is available.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">install()</span>

```ruby theme={null}
Microsandbox.install # => nil
```

Install the local runtime using the global configuration.

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">nil</span></div>
    <div className="msb-param-desc">No return value.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">default\_backend\_kind</span>

```ruby theme={null}
Microsandbox.default_backend_kind # => String
```

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">String</span></div>
    <div className="msb-param-desc">Current backend: local or cloud.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">use\_local\_backend!()</span>

```ruby theme={null}
Microsandbox.use_local_backend! # => nil
```

Select the local backend for subsequent operations.

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">nil</span></div>
    <div className="msb-param-desc">No return value.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">set\_runtime\_msb\_path()</span>

```ruby theme={null}
Microsandbox.set_runtime_msb_path(path) # => nil
```

Override the process-wide msb path. Set it before creating local sandboxes.

<p className="msb-label">Parameters</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><code>path</code><span className="msb-type">String</span></div>
    <div className="msb-param-desc">Path to the runtime executable.</div>
  </div>
</div>

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">nil</span></div>
    <div className="msb-param-desc">No return value.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">set\_runtime\_libkrunfw\_path()</span>

```ruby theme={null}
Microsandbox.set_runtime_libkrunfw_path(path) # => nil
```

Override the process-wide libkrunfw path. Set it before creating local sandboxes.

<p className="msb-label">Parameters</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><code>path</code><span className="msb-type">String</span></div>
    <div className="msb-param-desc">Path to the kernel firmware library.</div>
  </div>
</div>

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">nil</span></div>
    <div className="msb-param-desc">No return value.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">use\_cloud\_backend!()</span>

```ruby theme={null}
Microsandbox.use_cloud_backend!(api_key, url: nil) # => nil
```

<Accordion title="Example">
  ```ruby theme={null}
  Microsandbox.use_cloud_backend!(ENV.fetch("MSB_API_KEY"))
  ```
</Accordion>

Select the cloud backend for subsequent operations.

<p className="msb-label">Parameters</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><code>api\_key</code><span className="msb-type">String</span></div>
    <div className="msb-param-desc">Cloud API key.</div>
  </div>

  <div className="msb-param">
    <div className="msb-param-key"><code>url</code><span className="msb-type">String | nil</span></div>
    <div className="msb-param-desc">Optional API URL; nil uses the default cloud endpoint.</div>
  </div>
</div>

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">nil</span></div>
    <div className="msb-param-desc">No return value.</div>
  </div>
</div>

#### <span className="msb-recv">Microsandbox.</span><span className="msb-hn">use\_cloud\_profile!()</span>

```ruby theme={null}
Microsandbox.use_cloud_profile!(name) # => nil
```

Select a named cloud profile.

<p className="msb-label">Parameters</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><code>name</code><span className="msb-type">String</span></div>
    <div className="msb-param-desc">Configured cloud profile name.</div>
  </div>
</div>

<p className="msb-label">Returns</p>

<div className="msb-params">
  <div className="msb-param">
    <div className="msb-param-key"><span className="msb-type">nil</span></div>
    <div className="msb-param-desc">No return value.</div>
  </div>
</div>