# Generic cloud-init generator for Container Optimized OS
This helper module manages a `cloud-config` configuration that can start a container on [Container Optimized OS](https://cloud.google.com/container-optimized-os/docs) (COS). Either a complete `cloud-config` template can be provided via the `cloud_config` variable with optional template variables via the `config_variables`, or a generic `cloud-config` can be generated based on typical parameters needed to start a container.
Logging can be enabled via the [Google Cloud Logging docker driver](https://docs.docker.com/config/containers/logging/gcplogs/) using the `gcp_logging` variable. This is enabled by default, but requires that the service account running the COS instance have the `roles/logging.logWriter` IAM role or equivalent permissions on the project. If it doesn't, the container will fail to start unless this is disabled.
The module renders the generated cloud config in the `cloud_config` output, which can be directly used in instances or instance templates via the `user-data` metadata attribute.
## Examples
### Default configuration
This example will create a `cloud-config` that starts [Envoy Proxy](https://www.envoyproxy.io) and expose it on port 80. For a complete example, look at the sibling [`envoy-traffic-director`](../envoy-traffic-director/README.md) module that uses this module to start Envoy Proxy and connect it to [Traffic Director](https://cloud.google.com/traffic-director).
```hcl
module "cos-envoy" {
source = "./modules/cos-generic-metadata"
container_image = "envoyproxy/envoy:v1.14.1"
container_name = "envoy"
container_args = "-c /etc/envoy/envoy.yaml --log-level info --allow-unknown-static-fields"
| [authenticate_gcr](variables.tf#L112) | Setup docker to pull images from private GCR. Requires at least one user since the token is stored in the home of the first user defined. | <code>bool</code> | | <code>false</code> |
| [config_variables](variables.tf#L29) | Additional variables used to render the template passed via `cloud_config`. | <code>map(any)</code> | | <code>{}</code> |
| [files](variables.tf#L80) | Map of extra files to create on the instance, path as key. Owner and permissions will use defaults if null. | <codetitle="map(object({ content = string owner = string permissions = string }))">map(object({…}))</code> | | <code>{}</code> |
| [users](variables.tf#L102) | List of usernames to be created. If provided, first user will be used to run the container. | <codetitle="list(object({ username = string, uid = number, }))">list(object({…}))</code> | | <codetitle="[ ]">[…]</code> |