# Deploy software to machines

Deploy modules (hardware drivers, control logic, or other custom code) to one machine or an entire fleet. You configure the module in a fragment, apply the fragment to your machines, and the machines download the module from the Viam registry automatically.

## Prerequisites

- A module uploaded to the Viam registry. See [deploy a module](https://docs.viam.com/build-modules/deploy-a-module/) for how to upload.
- A [fragment](https://docs.viam.com/fleet/reuse-configuration/) for your fleet configuration. If you don’t have one yet, [create one](https://docs.viam.com/fleet/reuse-configuration/#create-a-fragment) first.

## 1. Add the module to a fragment

1. Navigate to your fragment’s page at [app.viam.com/fragments](https://app.viam.com/fragments).
2. Click **+** and select **Blocks**.
3. Search for your module in the registry and add it.
4. Configure the module’s attributes as needed.
5. Click **Save**.

## 2. Set the version strategy

Each module in the fragment has a version field. On the fragment card for the module, find the **Update version** section:

- **Latest version**: the machine downloads the newest version when it syncs. This is the default.
- **Pin to version**: the machine stays on a specific version and does not update automatically.
- **Pin to tag**: the machine uses whichever version the fragment tag points to. This option appears only when the fragment has tags. See [reuse configuration](https://docs.viam.com/fleet/reuse-configuration/#create-a-tag) for how to create tags.

#### Caution

For any version type other than pinning to a specific version, the module updates as soon as a matching version is available, which restarts the module. If the module cannot be safely interrupted, pin to a specific version and update manually.

To control when updates are applied, configure a maintenance window. See [manage versions](https://docs.viam.com/fleet/manage-versions/) for details.

## 3. Apply the fragment to machines

**Through the Viam app:**

1. Navigate to each machine’s **CONFIGURE** tab.
2. Click **+** and select **Blocks**.
3. Search for your fragment and select it.
4. Click **Add to machine**.
5. Click **Add to machine** again to confirm, then **Save**.

**Through provisioning:**

Include the fragment ID in your `viam-defaults.json` file. New machines apply the fragment automatically on first boot. See [provision devices](https://docs.viam.com/fleet/provision-devices/).

**Through the CLI:**

```sh
viam machines part fragments add --part=<part-id> --fragment=<fragment-name-or-id>
```

To find your part ID, run `viam machines part list --machine=<machine-id>`. Pass either the fragment’s name or its ID; find the ID on the fragment’s page in the Viam app, or run `viam organizations list` and check your fragments.

## 4. Verify the deployment

1. Navigate to a machine’s **CONFIGURE** tab and confirm the module appears in the resource list.
2. Go to the **CONTROL** tab and test the deployed components or services.
3. Check the **LOGS** tab for any errors from the module.

On the fleet dashboard at [app.viam.com/fleet/machines](https://app.viam.com/fleet/machines), confirm your machines are online. The dashboard does not currently show per-machine module versions; to verify the rollout reached every machine, see [verify a rollout across the fleet](https://docs.viam.com/fleet/manage-versions/#verify-a-rollout-across-the-fleet).