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72 changes: 72 additions & 0 deletions docs/ai-coder/agent-boundary.md
Original file line number Diff line number Diff line change
Expand Up @@ -102,3 +102,75 @@ You can also run Agent Boundaries directly in your workspace and configure it pe
```hcl
curl -fsSL https://raw.githubusercontent.com/coder/boundary/main/install.sh | bash
```

## Runtime & Permission Requirements for Running the Boundary in Docker

This section describes the Linux capabilities and runtime configurations required to run the Agent Boundary inside a Docker container. Requirements vary depending on the OCI runtime and the seccomp profile in use.

### 1. Default `runc` runtime with `CAP_NET_ADMIN`

When using Docker’s default `runc` runtime, the Boundary requires the container to have `CAP_NET_ADMIN`. This is the minimal capability needed for configuring virtual networking inside the container.

Docker’s default seccomp profile may also block certain syscalls (such as `clone`) required for creating unprivileged network namespaces. If you encounter these restrictions, you may need to update or override the seccomp profile to allow these syscalls.

[see Docker Seccomp Profile Considerations](#docker-seccomp-profile-considerations)

### 2. Default `runc` runtime with `CAP_SYS_ADMIN` (testing only)

For development or testing environments, you may grant the container `CAP_SYS_ADMIN`, which implicitly bypasses many of the restrictions in Docker’s default seccomp profile.

- The Boundary does not require `CAP_SYS_ADMIN` itself.
- However, Docker’s default seccomp policy commonly blocks namespace-related syscalls unless `CAP_SYS_ADMIN` is present.
- Granting `CAP_SYS_ADMIN` enables the Boundary to run without modifying the seccomp profile.

⚠️ Warning: `CAP_SYS_ADMIN` is extremely powerful and should not be used in production unless absolutely necessary.

### 3. `sysbox-runc` runtime with `CAP_NET_ADMIN`

When using the `sysbox-runc` runtime (from Nestybox), the Boundary can run with only:

- `CAP_NET_ADMIN`

The sysbox-runc runtime provides more complete support for unprivileged user namespaces and nested containerization, which typically eliminates the need for seccomp profile modifications.

## Docker Seccomp Profile Considerations

Docker’s default seccomp profile frequently blocks the `clone` syscall, which is required by the Boundary when creating unprivileged network namespaces. If the `clone` syscall is denied, the Boundary will fail to start.

To address this, you may need to modify or override the seccomp profile used by your container to explicitly allow the required `clone` variants.

You can find the default Docker seccomp profile for your Docker version here (specify your docker version):

https://github.com/moby/moby/blob/v25.0.13/profiles/seccomp/default.json#L628-L635

If the profile blocks the necessary `clone` syscall arguments, you can provide a custom seccomp profile that adds an allow rule like the following:

```json
{
"names": [
"clone"
],
"action": "SCMP_ACT_ALLOW"
}
```

This example unblocks the clone syscall entirely.

### Example: Overriding the Docker Seccomp Profile

To use a custom seccomp profile, start by downloading the default profile for your Docker version:

https://github.com/moby/moby/blob/v25.0.13/profiles/seccomp/default.json#L628-L635

Save it locally as seccomp-v25.0.13.json, then insert the clone allow rule shown above (or add "clone" to the list of allowed syscalls).

Once updated, you can run the container with the custom seccomp profile:

```bash
docker run -it \
--cap-add=NET_ADMIN \
--security-opt seccomp=seccomp-v25.0.13.json \
test bash
```

This instructs Docker to load your modified seccomp profile while granting only the minimal required capability (`CAP_NET_ADMIN`).
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