---
title: Alternative container runtimes
description: |
  Docker Engine uses runc as the default container runtime, but you
  can specify alternative runtimes using the CLI or by configuring
  the daemon
keywords: engine, runtime, containerd, runtime v2, shim
aliases:
  - /engine/alternative-runtimes/
---

Docker Engine uses containerd for managing the container lifecycle,
which includes creating, starting, and stopping containers.
By default, containerd uses runc as its container runtime.

## What runtimes can I use?

You can use any runtime that implements the containerd 
[shim API](https://github.com/containerd/containerd/blob/main/core/runtime/v2/README.md).
Such runtimes ship with a containerd shim, and you can use them without any
additional configuration. See [Use containerd shims](#use-containerd-shims).

Examples of runtimes that implement their own containerd shims include:

- [Wasmtime](https://wasmtime.dev/)
- [gVisor](https://github.com/google/gvisor)
- [Kata Containers](https://katacontainers.io/)

You can also use runtimes designed as drop-in replacements for runc. Such
runtimes depend on the runc containerd shim for invoking the runtime binary.
You must manually register such runtimes in the daemon configuration.

[youki](https://github.com/youki-dev/youki)
is one example of a runtime that can function as a runc drop-in replacement.
Refer to the [youki example](#youki) explaining the setup.

## Use containerd shims

containerd shims let you use alternative runtimes without having to change the
configuration of the Docker daemon. To use a containerd shim, install the shim
binary on `PATH` on the system where the Docker daemon is running.

To use a shim with `docker run`, specify the fully qualified name of the
runtime as the value to the `--runtime` flag:

```console
$ docker run --runtime io.containerd.kata.v2 hello-world
```

### Use a containerd shim without installing on PATH

You can use a shim without installing it on `PATH`, in which case you need to
register the shim in the daemon configuration as follows:

```json
{
  "runtimes": {
    "foo": {
      "runtimeType": "/path/to/containerd-shim-foobar-v1"
    }
  }
}
```

To use the shim, specify the name that you assigned to it:

```console
$ docker run --runtime foo hello-world
```

### Configure shims

If you need to pass additional configuration for a containerd shim, you can
use the `runtimes` option in the daemon configuration file.

1. Edit the daemon configuration file by adding a `runtimes` entry for the
   shim you want to configure.

   - Specify the fully qualified name for the runtime in `runtimeType` key
   - Add your runtime configuration under the `options` key

   ```json
   {
     "runtimes": {
       "gvisor": {
         "runtimeType": "io.containerd.runsc.v1",
         "options": {
           "TypeUrl": "io.containerd.runsc.v1.options",
           "ConfigPath": "/etc/containerd/runsc.toml"
         }
       }
     }
   }
   ```

2. Reload the daemon's configuration.

   ```console
   # systemctl reload docker
   ```

3. Use the customized runtime using the `--runtime` flag for `docker run`.

   ```console
   $ docker run --runtime gvisor hello-world
   ```

For more information about the configuration options for containerd shims, see
[Configure containerd shims](/reference/cli/dockerd.md#configure-containerd-shims).

## Examples

The following examples show you how to set up and use alternative container