# Specify a bind mount in an Amazon ECS task definition
<a name="specify-bind-mount-config"></a>

For Amazon ECS tasks that are hosted on either Fargate or Amazon EC2 instances, the following task definition JSON snippet shows the syntax for the `volumes`, `mountPoints`, and `ephemeralStorage` objects for a task definition.

```
{
   "family": "",
   ...
   "containerDefinitions" : [
      {
         "mountPoints" : [
            {
               "containerPath" : "{{/path/to/mount_volume}}",
               "sourceVolume" : "{{string}}"
            }
          ],
          "name" : "{{string}}"
       }
    ],
    ...
    "volumes" : [
       {
          "name" : "{{string}}"
       }
    ],
    "ephemeralStorage": {
	   "sizeInGiB": {{integer}}
    }
}
```

For Amazon ECS tasks that are hosted on Amazon EC2 instances, you can use the optional `host` parameter and a `sourcePath` when specifying the task volume details. When it's specified, it ties the bind mount to the lifecycle of the task rather than the container.

```
"volumes" : [
    {
        "host" : {
            "sourcePath" : "{{string}}"
        },
        "name" : "{{string}}"
    }
]
```

The following describes each task definition parameter in more detail.

`name`  
Type: String  
Required: No  
The name of the volume. Up to 255 letters (uppercase and lowercase), numbers, hyphens (`-`), and underscores (`_`) are allowed. This name is referenced in the `sourceVolume` parameter of the container definition `mountPoints` object.

`host`  
Required: No  
The `host` parameter is used to tie the lifecycle of the bind mount to the host Amazon EC2 instance, rather than the task, and where it is stored. If the `host` parameter is empty, then the Docker daemon assigns a host path for your data volume, but the data is not guaranteed to persist after the containers associated with it stop running.  
Windows containers can mount whole directories on the same drive as `$env:ProgramData`.  
The `sourcePath` parameter is supported only when using tasks that are hosted on Amazon EC2 instances or Amazon ECS Managed Instances.  
`sourcePath`  
Type: String  
Required: No  
When the `host` parameter is used, specify a `sourcePath` to declare the path on the host Amazon EC2 instance that is presented to the container. If this parameter is empty, then the Docker daemon assigns a host path for you. If the `host` parameter contains a `sourcePath` file location, then the data volume persists at the specified location on the host Amazon EC2 instance until you delete it manually. If the `sourcePath` value does not exist on the host Amazon EC2 instance, the Docker daemon creates it. If the location does exist, the contents of the source path folder are exported.

`mountPoints`  
Type: Object array  
Required: No  
The mount points for the data volumes in your container. This parameter maps to `Volumes` in the create-container Docker API and the `--volume` option to docker run.  
Windows containers can mount whole directories on the same drive as `$env:ProgramData`. Windows containers cannot mount directories on a different drive, and mount points cannot be used across drives. You must specify mount points to attach an Amazon EBS volume directly to an Amazon ECS task.    
`sourceVolume`  
Type: String  
Required: Yes, when `mountPoints` are used  
The name of the volume to mount.  
`containerPath`  
Type: String  
Required: Yes, when `mountPoints` are used  
The path in the container where the volume will be mounted.  
`readOnly`  
Type: Boolean  
Required: No  
If this value is `true`, the container has read-only access to the volume. If this value is `false`, then the container can write to the volume. The default value is `false`.  
For tasks that run on EC2 instances running the Windows operating system, leave the value as the default of `false`.

`ephemeralStorage`  
Type: Object  
Required: No  
The amount of ephemeral storage to allocate for the task. This parameter is used to expand the total amount of ephemeral storage available, beyond the default amount, for tasks hosted on Amazon Fargate using platform version `1.4.0` or later (Linux) or `1.0.0` or later (Windows).  
You can use the Copilot CLI, CloudFormation, the Amazon SDK or the CLI to specify ephemeral storage for a bind mount.