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# How to configure Ubuntu Pro guest attachment

If [Ubuntu Pro](https://ubuntu.com/pro) is enabled on a LXD host, guest instances can be automatically attached to the Pro subscription on that host.

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## Requirements

- Ubuntu Pro must be enabled on the LXD host server.
- The Pro client must be updated to the latest version.

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## Configure guest attachment

On the LXD host, run:

```bash
sudo pro config set lxd_guest_attach=<on|off|available>
```

The allowed values are:

- `on`: New LXD guest instances are automatically attached to the host’s Pro subscription.
- `off`: Default if unset. LXD guest instances cannot be attached to the host’s Pro subscription.
- `available`: New LXD guest instances on the host are not attached automatically, but can be attached using the `pro auto-attach` command in the guest.

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## Automatic attachment

If `lxd_guest_attach=on` is set, instances automatically attach to its host’s Pro subscription at startup. The initial attach process can take some time. To confirm the subscription, run:

```bash
lxc exec <guest-instance> -- pro status
```

If the attach process has not completed, you will see the following lines within the output:

```bash
NOTICES
Operation in progress: pro.daemon.attempt_auto_attach
```

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## Force attachment

Guest instances that were started prior to setting `lxd_guest_attach=on` on the host will not automatically attach to the host’s Pro subscription. Neither will any instances on a host set to `lxd_guest_attach=available`.

To force such instances to attach, run:

```bash
lxc exec <guest-instance> -- pro auto-attach
```

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## Instance-level override

The `lxd_guest_attach` setting on the host can be overridden at the instance level, through the [`ubuntu_pro.guest_attach`](https://canonical.com/lxd/docs/default/reference/instance_options/index.html.md#instance-miscellaneous:ubuntu_pro.guest_attach) configuration option. The `ubuntu_pro.guest_attach` configuration key has three options: `on`, `off`, and `available`.

For example, if `lxd_guest_attach` is set to `on` on the host and you want to prevent Pro attachment in a new guest instance you are launching, run:

```bash
lxc launch ubuntu:24.04 <guest-instance> -c ubuntu_pro.guest_attach=off
```

To set this key on an instance that has already been created, see: [Configure instance options](https://canonical.com/lxd/docs/default/howto/instances_configure/index.html.md#instances-configure-options).

All options for Pro guest attachment are described below.

|                     | `on (host)`                 | `available (host)`          | `off (host)`              | `unset (host)`            |
|---------------------|-----------------------------|-----------------------------|---------------------------|---------------------------|
| `on (guest)`        | auto-attach on start        | auto-attach on start        | guest attachment disabled | guest attachment disabled |
| `available (guest)` | attach on `pro auto-attach` | attach on `pro-auto-attach` | guest attachment disabled | guest attachment disabled |
| `off (guest)`       | guest attachment disabled   | guest attachment disabled   | guest attachment disabled | guest attachment disabled |
| `unset (guest)`     | auto-attach on start        | attach on `pro-auto-attach` | guest attachment disabled | guest attachment disabled |