How to allow Container with read only root filesystem writing to tmpfs-volume?

Question

i have the following problem:

my nginx container is starting with read only root-filesystem and i have configured two tmpfs-mounts: /var/run and /var/cache/nginx like it's described there: https://hub.docker.com/_/nginx

At startup nginx throws this error and the container stops: 2021/08/26 06:31:16 [emerg] 1#1: mkdir() "/var/cache/nginx/client_temp" failed (30: Read-only file system)

This is my ecs task-config:

{ 
    "name": "nginx", 
    "essential": false,
    "readonlyRootFilesystem": true,
    "healthCheck": {
        "command": [
          "CMD-SHELL",
          "curl  --fail 127.0.0.1 || exit 1"
        ],
        "interval": 30,
        "timeout": 2,
        "retries": 3
      },
    "memory": 256,
    "image": "###########.dkr.ecr.eu-central-1.amazonaws.com/nginx:${NGINX_VER}",
    "dockerLabels":
      {
        "Name": "nginx",
        "Component": "sidecar-prometheus",
        "App-Version": "${NGINX_VER}"
      },
    "logConfiguration": {
      "logDriver": "awslogs",
      "options": {
         "awslogs-group": "${LOG_GROUP_NAME}",
         "awslogs-region": "eu-central-1",
         "awslogs-stream-prefix": "${LOG_GROUP_NAME}"
      }
    },
    "portMappings": [
      {
        "containerPort": 10000,
        "hostPort": 10000,
        "protocol": "tcp"
      }
    ],  
    "mountPoints": [
      {
        "readOnly": false,
        "containerPath": "/config",
        "sourceVolume": "VolumeConfig"
      }
    ],
    "tmpfs": {
        "containerPath": "/var/run",
        "size": "50",
        "mountOptions": "rw"
    },
    "tmpfs": {
        "containerPath": "/var/cache/nginx",
        "size": "50",
        "mountOptions": "rw"
    },

How can i make the /var/cache/nginx mount rw ?

Many thanks for helping !

Answer 1

The answer is that the config was wrong !

Here is the right way, tmpfs must include in linuxParameters:

"linuxParameters": {
    "tmpfs": [
      {
        "containerPath": "/var/log/nginx",
        "mountOptions": [ "rw" ],
        "size": 50
      },
      {
        "mountOptions": [ "rw" ],
        "containerPath": "/run",
        "size": 10
      },
      {
        "mountOptions": [ "rw"],
        "containerPath": "/var/cache/nginx",
        "size": 10
      },
      {
        "mountOptions": [ "rw"],
        "containerPath": "/tmp",
        "size": 10
      }
    ]
    }