When the container has started, Buildx submits the build submitted to the
containerized build server.

```console
$ docker buildx build -t <image> --builder=container .
WARNING: No output specified with docker-container driver. Build result will only remain in the build cache. To push result image into registry use --push or to load image into docker use --load
#1 [internal] booting buildkit
#1 pulling image moby/buildkit:buildx-stable-1
#1 pulling image moby/buildkit:buildx-stable-1 1.9s done
#1 creating container buildx_buildkit_container0
#1 creating container buildx_buildkit_container0 0.5s done
#1 DONE 2.4s
...
```

## Cache persistence

The `docker-container` driver supports cache persistence, as it stores all the
BuildKit state and related cache into a dedicated Docker volume.

To persist the `docker-container` driver's cache, even after recreating the
driver using `docker buildx rm` and `docker buildx create`, you can destroy the
builder using the `--keep-state` flag:

For example, to create a builder named `container` and then remove it while
persisting state:

```console
# setup a builder
$ docker buildx create --name=container --driver=docker-container --use --bootstrap
container
$ docker buildx ls
NAME/NODE       DRIVER/ENDPOINT              STATUS   BUILDKIT PLATFORMS
container *     docker-container
  container0    desktop-linux                running  v0.10.5  linux/amd64
$ docker volume ls
DRIVER    VOLUME NAME
local     buildx_buildkit_container0_state

# remove the builder while persisting state
$ docker buildx rm --keep-state container
$ docker volume ls
DRIVER    VOLUME NAME
local     buildx_buildkit_container0_state

# the newly created driver with the same name will have all the state of the previous one!
$ docker buildx create --name=container --driver=docker-container --use --bootstrap
container
```

## QEMU

The `docker-container` driver supports using [QEMU](https://www.qemu.org/)
(user mode) to build non-native platforms. Use the `--platform` flag to specify
which architectures that you want to build for.

For example, to build a Linux image for `amd64` and `arm64`:

```console
$ docker buildx build \
  --builder=container \
  --platform=linux/amd64,linux/arm64 \
  -t <registry>/<image> \
  --push .
```

> [!NOTE]
>
> Emulation with QEMU can be much slower than native builds, especially for
> compute-heavy tasks like compilation and compression or decompression.

## Custom network

You can customize the network that the builder container uses. This is useful
if you need to use a specific network for your builds.

For example, let's [create a network](/reference/cli/docker/network/create.md)
named `foonet`:

```console
$ docker network create foonet
```

Now create a [`docker-container` builder](/reference/cli/docker/buildx/create.md)
that will use this network:

```console
$ docker buildx create --use \
  --name mybuilder \
  --driver docker-container \
  --driver-opt "network=foonet"
```

Boot and [inspect `mybuilder`](/reference/cli/docker/buildx/inspect.md):

```console
$ docker buildx inspect --bootstrap
```

[Inspect the builder container](/reference/cli/docker/inspect.md)
and see what network is being used:

```console
$ docker inspect buildx_buildkit_mybuilder0 --format={{.NetworkSettings.Networks}}
map[foonet:0xc00018c0c0]
```

## Further reading

For more information on the Docker container driver, see the
[buildx reference](/reference/cli/docker/buildx/create.md#driver).