This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

You can read more about this in the [Advanced User Guide](../advanced/index.md){.internal-link target=_blank}.

## Details

This sub-application is just another standard FastAPI application, but this is the one that will be "mounted":

```Python hl_lines="11  14-16"
{!../../docs_src/sub_applications/tutorial001.py!}
```

### Mount the sub-application

In your top-level application, `app`, mount the sub-application, `subapi`.

In this case, it will be mounted at the path `/subapi`:

```Python hl_lines="11  19"

// under the procfs, /proc/<pid>/ns/net. In majority of cases, this is not used directly, but is rather bind mounted to
// /var/run/netns/<name>. However, this pattern is not ubiquitous. Some platforms bind mount to other places. As we run
// in a pod, we cannot just access any arbitrary file they happen to bind mount in, as we don't know ahead of time where
// it might be.
//
// Instead, we rely directly on the procfs.

  // portworxVolume represents a portworx volume attached and mounted on kubelets host machine
  // +optional
  optional PortworxVolumeSource portworxVolume = 24;

  // scaleIO represents a ScaleIO persistent volume attached and mounted on Kubernetes nodes.
  // +optional
  optional ScaleIOVolumeSource scaleIO = 25;

  // storageOS represents a StorageOS volume attached and mounted on Kubernetes nodes.
  // +optional

# This bazelrc can build a CPU-supporting TF package.

# Convenient cache configurations
# Use a cache directory mounted to /tf/cache. Very useful!
build:sigbuild_local_cache --disk_cache=/tf/cache
# Use the public-access TF DevInfra cache (read only)
build:sigbuild_remote_cache --remote_cache="https://storage.googleapis.com/tensorflow-devinfra-bazel-cache/manylinux2014" --remote_upload_local_results=false

// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package disk

import "runtime"

// IsRootDisk returns if diskPath belongs to root-disk, i.e the disk mounted at "/"
func IsRootDisk(diskPath string, rootDisk string) (bool, error) {
	if runtime.GOOS == "windows" {
		// On windows this function is not implemented.
		return false, nil
	}
	return SameDisk(diskPath, rootDisk)

# This bazelrc can build a CPU-supporting TF package.

# Convenient cache configurations
# Use a cache directory mounted to /tf/cache. Very useful!
build:sigbuild_local_cache --disk_cache=/tf/cache
# Use the public-access TF DevInfra cache (read only)
build:sigbuild_remote_cache --remote_cache="https://storage.googleapis.com/tensorflow-devinfra-bazel-cache/manylinux2014" --remote_upload_local_results=false

	"unsafe"
)

// GetVolumeInformation provides windows drive volume information.
var GetVolumeInformation = kernel32.NewProc("GetVolumeInformationW")

// getFSType returns the filesystem type of the underlying mounted filesystem
func getFSType(path string) string {
	volumeNameSize, nFileSystemNameSize := uint32(260), uint32(260)
	var lpVolumeSerialNumber uint32
	var lpFileSystemFlags, lpMaximumComponentLength uint32

	"ef53":     "EXT4",
	"f15f":     "ecryptfs",
	"794c7630": "overlayfs",
	"2fc12fc1": "zfs",
	"ff534d42": "cifs",
	"53464846": "wslfs",
}

// getFSType returns the filesystem type of the underlying mounted filesystem
func getFSType(ftype uint32) string {
	fsTypeHex := strconv.FormatUint(uint64(ftype), 16)
	fsTypeString, ok := fsType2StringMap[fsTypeHex]
	if !ok {
		return "UNKNOWN"
	}
	return fsTypeString
}

// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package disk

// getFSType returns the filesystem type of the underlying mounted filesystem
func getFSType(fstype []int8) string {
	b := make([]byte, len(fstype))
	for i, v := range fstype {
		b[i] = byte(v)
	}
	return string(b)