Fairwinds Polaris vs Open Policy Agent Gatekeeper

Fairwinds Polaris is an open source policy engine for validating and remediating Kubernetes resource configuration. It includes more than 30 built-in policies, and teams can add their own using JSON Schema. Checks cover security practices such as least privilege, privilege escalation, root execution, and host IPC or PID settings, along with resource requests and limits, readiness and liveness probes, and image tags. Polaris can run as a dashboard, an admission controller, or a command-line tool for checking local YAML files in CI/CD. Its validating webhook rejects workloads that trigger danger-level checks; warning-level findings pass and appear in the dashboard or webhook logs. A mutating webhook or command-line run can automatically remediate supported issues, including missing limits and probes and some unsafe security settings. The dashboard can audit local files or connect to a live cluster, and can be installed with kubectl or Helm. The validating webhook requires a valid TLS certificate. Polaris is free and runs on Linux, macOS, Windows, web, and self-hosted environments.

Open Policy Agent Gatekeeper is a free, open-source Kubernetes policy controller for Linux and self-hosted deployments. It runs as a validating and mutating webhook, enforcing CRD-based policies evaluated by Open Policy Agent. Validation constraints can deny requests, warn, run in dry-run mode or report violations without changing resources. Mutation policies can alter matching resources during admission before validation checks the final object. An audit function periodically evaluates existing cluster resources against constraints to identify pre-existing misconfigurations. The project includes an extensible policy library with parameterized examples, and provider connections to external data such as image registries and directory services. Named integrations or backed services include Azure Policy for Kubernetes, Google Kubernetes Engine Policy Controller, Rancher, AWS EKS Blueprints and Alibaba Cloud. Installation options include prebuilt, development or locally built images and Helm. Gatekeeper requires Kubernetes resources introduced in version 1.16 and cluster-admin permissions for installation. The gator CLI is documented as beta from version 3.11.