# Bind mount examples for Amazon ECS The following examples cover the common use cases for using a bind mount for your containers. **To allocate an increased amount of ephemeral storage space for a Fargate task** For Amazon ECS tasks that are hosted on Fargate using platform version `1.4.0` or later (Linux) or `1.0.0` (Windows), you can allocate more than the default amount of ephemeral storage for the containers in your task to use. This example can be incorporated into the other examples to allocate more ephemeral storage for your Fargate tasks. + In the task definition, define an `ephemeralStorage` object. The `sizeInGiB` must be an integer between the values of `21` and `200` and is expressed in GiB. ``` "ephemeralStorage": { "sizeInGiB": integer } ``` **To provide an empty data volume for one or more containers** In some cases, you want to provide the containers in a task some scratch space. For example, you might have two database containers that need to access the same scratch file storage location during a task. This can be achieved using a bind mount. 1. In the task definition `volumes` section, define a bind mount with the name `database_scratch`. ``` "volumes": [ { "name": "database_scratch" } ] ``` 1. In the `containerDefinitions` section, create the database container definitions. This is so that they mount the volume. ``` "containerDefinitions": [ { "name": "database1", "image": "my-repo/database", "cpu": 100, "memory": 100, "essential": true, "mountPoints": [ { "sourceVolume": "database_scratch", "containerPath": "/var/scratch" } ] }, { "name": "database2", "image": "my-repo/database", "cpu": 100, "memory": 100, "essential": true, "mountPoints": [ { "sourceVolume": "database_scratch", "containerPath": "/var/scratch" } ] } ] ``` **To expose a path and its contents in a Dockerfile to a container** In this example, you have a Dockerfile that writes data that you want to mount inside a container. This example works for tasks that are hosted on Fargate or Amazon EC2 instances. 1. Create a Dockerfile. The following example uses the public Amazon Linux 2 container image and creates a file that's named `examplefile` in the `/var/log/exported` directory that we want to mount inside the container. The `VOLUME` directive should specify an absolute path. ``` FROM public.ecr.aws/amazonlinux/amazonlinux:latest RUN mkdir -p /var/log/exported RUN touch /var/log/exported/examplefile VOLUME ["/var/log/exported"] ``` By default, the volume permissions are set to `0755` and the owner as `root`. These permissions can be changed in the Dockerfile. In the following example, the owner of the `/var/log/exported` directory is set to `node`. ``` FROM public.ecr.aws/amazonlinux/amazonlinux:latest RUN yum install -y shadow-utils && yum clean all RUN useradd node RUN mkdir -p /var/log/exported && chown node:node /var/log/exported USER node RUN touch /var/log/exported/examplefile VOLUME ["/var/log/exported"] ``` 1. In the task definition `volumes` section, define a volume with the name `application_logs`. ``` "volumes": [ { "name": "application_logs" } ] ``` 1. In the `containerDefinitions` section, create the application container definitions. This is so they mount the storage. The `containerPath` value must match the absolute path that's specified in the `VOLUME` directive from the Dockerfile. ``` "containerDefinitions": [ { "name": "application1", "image": "my-repo/application", "cpu": 100, "memory": 100, "essential": true, "mountPoints": [ { "sourceVolume": "application_logs", "containerPath": "/var/log/exported" } ] }, { "name": "application2", "image": "my-repo/application", "cpu": 100, "memory": 100, "essential": true, "mountPoints": [ { "sourceVolume": "application_logs", "containerPath": "/var/log/exported" } ] } ] ``` **To provide an empty data volume for a container that's tied to the lifecycle of the host Amazon EC2 instance** For tasks that are hosted on Amazon EC2 instances, you can use bind mounts and have the data tied to the lifecycle of the host Amazon EC2 instance. You can do this by using the `host` parameter and specifying a `sourcePath` value. Any files that exist at the `sourcePath` are presented to the containers at the `containerPath` value. Any files that are written to the `containerPath` value are written to the `sourcePath` value on the host Amazon EC2 instance. **Important** Amazon ECS doesn't sync your storage across Amazon EC2 instances. Tasks that use persistent storage can be placed on any Amazon EC2 instance in your cluster that has available capacity. If your tasks require persistent storage after stopping and restarting, always specify the same Amazon EC2 instance at task launch time with the AWS CLI [start-task](https://docs.aws.amazon.com/cli/latest/reference/ecs/start-task.html) command. You can also use Amazon EFS volumes for persistent storage. For more information, see [Use Amazon EFS volumes with Amazon ECS](efs-volumes.md). 1. In the task definition `volumes` section, define a bind mount with `name` and `sourcePath` values. In the following example, the host Amazon EC2 instance contains data at `/ecs/webdata` that you want to mount inside the container. ``` "volumes": [ { "name": "webdata", "host": { "sourcePath": "/ecs/webdata" } } ] ``` 1. In the `containerDefinitions` section, define a container with a `mountPoints` value that references the name of the bind mount and the `containerPath` value to mount the bind mount at on the container. ``` "containerDefinitions": [ { "name": "web", "image": "public.ecr.aws/docker/library/nginx:latest", "cpu": 99, "memory": 100, "portMappings": [ { "containerPort": 80, "hostPort": 80 } ], "essential": true, "mountPoints": [ { "sourceVolume": "webdata", "containerPath": "/usr/share/nginx/html" } ] } ] ``` **To mount a defined volume on multiple containers at different locations** You can define a data volume in a task definition and mount that volume at different locations on different containers. For example, your host container has a website data folder at `/data/webroot`. You might want to mount that data volume as read-only on two different web servers that have different document roots. 1. In the task definition `volumes` section, define a data volume with the name `webroot` and the source path `/data/webroot`. ``` "volumes": [ { "name": "webroot", "host": { "sourcePath": "/data/webroot" } } ] ``` 1. In the `containerDefinitions` section, define a container for each web server with `mountPoints` values that associate the `webroot` volume with the `containerPath` value pointing to the document root for that container. ``` "containerDefinitions": [ { "name": "web-server-1", "image": "my-repo/ubuntu-apache", "cpu": 100, "memory": 100, "portMappings": [ { "containerPort": 80, "hostPort": 80 } ], "essential": true, "mountPoints": [ { "sourceVolume": "webroot", "containerPath": "/var/www/html", "readOnly": true } ] }, { "name": "web-server-2", "image": "my-repo/sles11-apache", "cpu": 100, "memory": 100, "portMappings": [ { "containerPort": 8080, "hostPort": 8080 } ], "essential": true, "mountPoints": [ { "sourceVolume": "webroot", "containerPath": "/srv/www/htdocs", "readOnly": true } ] } ] ``` **To mount volumes from another container using `volumesFrom`** For tasks hosted on Amazon EC2 instances, you can define one or more volumes on a container, and then use the `volumesFrom` parameter in a different container definition within the same task to mount all of the volumes from the `sourceContainer` at their originally defined mount points. The `volumesFrom` parameter applies to volumes defined in the task definition, and those that are built into the image with a Dockerfile. 1. (Optional) To share a volume that is built into an image, use the `VOLUME` instruction in the Dockerfile. The following example Dockerfile uses an `httpd` image, and then adds a volume and mounts it at `dockerfile_volume` in the Apache document root. It is the folder used by the `httpd` web server. ``` FROM httpd VOLUME ["/usr/local/apache2/htdocs/dockerfile_volume"] ``` You can build an image with this Dockerfile and push it to a repository, such as Docker Hub, and use it in your task definition. The example `my-repo/httpd_dockerfile_volume` image that's used in the following steps was built with the preceding Dockerfile. 1. Create a task definition that defines your other volumes and mount points for the containers. In this example `volumes` section, you create an empty volume called `empty`, which the Docker daemon manages. There's also a host volume defined that's called `host_etc`. It exports the `/etc` folder on the host container instance. ``` { "family": "test-volumes-from", "volumes": [ { "name": "empty", "host": {} }, { "name": "host_etc", "host": { "sourcePath": "/etc" } } ], ``` In the container definitions section, create a container that mounts the volumes defined earlier. In this example, the `web` container mounts the `empty` and `host_etc` volumes. This is the container that uses the image built with a volume in the Dockerfile. ``` "containerDefinitions": [ { "name": "web", "image": "my-repo/httpd_dockerfile_volume", "cpu": 100, "memory": 500, "portMappings": [ { "containerPort": 80, "hostPort": 80 } ], "mountPoints": [ { "sourceVolume": "empty", "containerPath": "/usr/local/apache2/htdocs/empty_volume" }, { "sourceVolume": "host_etc", "containerPath": "/usr/local/apache2/htdocs/host_etc" } ], "essential": true }, ``` Create another container that uses `volumesFrom` to mount all of the volumes that are associated with the `web` container. All of the volumes on the `web` container are likewise mounted on the `busybox` container. This includes the volume that's specified in the Dockerfile that was used to build the `my-repo/httpd_dockerfile_volume` image. ``` { "name": "busybox", "image": "busybox", "volumesFrom": [ { "sourceContainer": "web" } ], "cpu": 100, "memory": 500, "entryPoint": [ "sh", "-c" ], "command": [ "echo $(date) > /usr/local/apache2/htdocs/empty_volume/date && echo $(date) > /usr/local/apache2/htdocs/host_etc/date && echo $(date) > /usr/local/apache2/htdocs/dockerfile_volume/date" ], "essential": false } ] } ``` When this task is run, the two containers mount the volumes, and the `command` in the `busybox` container writes the date and time to a file. This file is called `date` in each of the volume folders. The folders are then visible at the website displayed by the `web` container. **Note** Because the `busybox` container runs a quick command and then exits, it must be set as `"essential": false` in the container definition. Otherwise, it stops the entire task when it exits.