Ensure Container-Optimized OS (cos) is used for Kubernetes Engine Clusters Node image
Default Severity: low
Explanation
GKE supports several OS image types but COS is the recommended OS image to use on cluster nodes for enhanced security
Possible Impact
COS is the recommended OS image to use on cluster nodes
Suggested Resolution
Use the COS image type
Insecure Example
The following example will fail the google-gke-node-pool-uses-cos check.
resource "google_service_account" "default" {
account_id = "service-account-id"
display_name = "Service Account"
}
resource "google_container_cluster" "primary" {
name = "my-gke-cluster"
location = "us-central1"
# We can't create a cluster with no node pool defined, but we want to only use
# separately managed node pools. So we create the smallest possible default
# node pool and immediately delete it.
remove_default_node_pool = true
initial_node_count = 1
}
resource "google_container_node_pool" "bad_example" {
name = "my-node-pool"
cluster = google_container_cluster.primary.id
node_count = 1
node_config {
preemptible = true
machine_type = "e2-medium"
# Google recommends custom service accounts that have cloud-platform scope and permissions granted via IAM Roles.
service_account = google_service_account.default.email
oauth_scopes = [
"https://www.googleapis.com/auth/cloud-platform"
]
image_type = "something"
}
}
Secure Example
The following example will pass the google-gke-node-pool-uses-cos check.
resource "google_service_account" "default" {
account_id = "service-account-id"
display_name = "Service Account"
}
resource "google_container_cluster" "primary" {
name = "my-gke-cluster"
location = "us-central1"
# We can't create a cluster with no node pool defined, but we want to only use
# separately managed node pools. So we create the smallest possible default
# node pool and immediately delete it.
remove_default_node_pool = true
initial_node_count = 1
}
resource "google_container_node_pool" "good_example" {
name = "my-node-pool"
cluster = google_container_cluster.primary.id
node_count = 1
node_config {
preemptible = true
machine_type = "e2-medium"
# Google recommends custom service accounts that have cloud-platform scope and permissions granted via IAM Roles.
service_account = google_service_account.default.email
oauth_scopes = [
"https://www.googleapis.com/auth/cloud-platform"
]
image_type = "COS"
}
}