Accessing rexray/ebs volume from ECS host

I've managed to follow https://aws.amazon.com/blogs/compute/amazon-ecs-and-docker-volume-drivers-amazon-ebs/ and run my Container-based service on ECS using rex-ray Docker volume plugin. I can see that my service is generating data inside the volume by logging into the Docker container using docker exec -it <id> /bin/sh

Is there a place on the host EC2 instance where I can check that data? Is the rex-ray volume mounted anywhere on the host instance?

I'm running a single node ECS cluster. I used the following Task definition. I declared sourcePath in host under volumes, but I don't see any outputs directory on the host container.

{
"ipcMode": null,
"executionRoleArn": null,
"containerDefinitions": [
    {
        "dnsSearchDomains": null,
        "environmentFiles": null,
        "logConfiguration": {
            "logDriver": "awslogs",
            "secretOptions": null,
            "options": {
                "awslogs-group": "/ecs/xxxxx",
                "awslogs-region": "us-east-1",
                "awslogs-stream-prefix": "ecs"
            }
        },
        "entryPoint": null,
        "portMappings": [],
        "command": null,
        "linuxParameters": null,
        "cpu": 0,
        "environment": [
            {
                "name": "save_path",
                "value": "/outputs"
            },
            {
                "name": "watchdog_limit",
                "value": "60"
            },
            {
                "name": "max_records_per_file",
                "value": "14400"
            }
        ],
        "resourceRequirements": null,
        "ulimits": null,
        "dnsServers": null,
        "mountPoints": [
            {
                "readOnly": null,
                "containerPath": "/outputs",
                "sourceVolume": "rexray_volume"
            }
        ],
        "workingDirectory": null,
        "secrets": null,
        "dockerSecurityOptions": null,
        "memory": null,
        "memoryReservation": 300,
        "volumesFrom": [],
        "stopTimeout": null,
        "image": "xxxxxxxxxxxxxxx.dkr.ecr.us-east-1.amazonaws.com/xxxxxxxxx:1.1",
        "startTimeout": null,
        "firelensConfiguration": null,
        "dependsOn": null,
        "disableNetworking": null,
        "interactive": null,
        "healthCheck": null,
        "essential": true,
        "links": null,
        "hostname": null,
        "extraHosts": null,
        "pseudoTerminal": null,
        "user": null,
        "readonlyRootFilesystem": null,
        "dockerLabels": null,
        "systemControls": null,
        "privileged": null,
        "name": "Datafeed"
    }
],
"memory": null,
"taskRoleArn": null,
"family": "Xxxxxxxx",
"pidMode": null,
"requiresCompatibilities": [
    "EC2"
],
"networkMode": null,
"cpu": null,
"inferenceAccelerators": [],
"proxyConfiguration": null,
"volumes": [
    {
        "fsxWindowsFileServerVolumeConfiguration": null,
        "efsVolumeConfiguration": null,
        "name": "rexray_volume",
        "host": {
            "sourcePath": "/outputs"
        },
        "dockerVolumeConfiguration": {
            "autoprovision": true,
            "scope": "shared",
            "driver": "rexray/ebs",
            "driverOpts": {
                "volumetype": "gp3",
                "size": "20"
            }
        }
    }
],
"placementConstraints": [],
"tags": []

}

Solution 1:

I managed to access the files. The device is already mounted to a path inside /var/lib/docker/plugins folder.

This can be identified using the command lsblk. Since the device is already mounted, it can't be mounted again to a different location, however, you can create a --bind mount to a more convenient location.

sudo mount --bind /var/lib/docker/plugins/xxxxxx/propagated-mount/volumes/rexray_vol outputs/

I do need to su to access the files though. Let me know if you have any better solution.