Skip to main content

Cloud Custodian - Policy Rules Engine

Project description

Join the chat at Build Status License Requirements Status

Cloud Custodian

Cloud Custodian is a rules engine for AWS fleet management. It allows users to define policies to enable a well managed cloud infrastructure, that’s both secure, and cost optimized. It consolidates many of the adhoc scripts organizations have into a lightweight and flexible tool, with unified metrics and reporting.

Custodian can be used manage to AWS accounts by ensuring real time compliance to security policies (like encryption and access requirements), tag policies and cost management via garbage collection of unused resources and off-hours resource management for examples.

Custodian policies are written in simple YAML configuration files that enable specify policies on a resource type (ec2, asg, redshift, etc) and are constructed from a vocabulary of filters and actions.

It integrates with lambda and cloudwatch events to provide for realtime enforcement of policies with builtin provisioning of the lambdas, or as a simple cron job on a server to execute against large existing fleets.


  • Comprehensive support for aws services and resources (~50), along with 65 unique actions and 75 filters to build policies with.

  • Supports arbitrary filtering on resources with nested boolean conditions.

  • Dry run any policy to see what it would do.

  • Automatically provisions lambda functions and cloud watch event targets for real-time policies.

  • Cloudwatch metrics outputs on resources that matched a policy

  • Structured outputs into s3 of which resources matched a policy.

  • Utilizes a cache utilization, to minimize api calls.

  • Battle-tested, In production on against some very large aws accounts.

  • Supports cross account usage via STS role assumption.

  • Supports integration with custom/user supplied lambdas as actions.

Quick Install

$ virtualenv custodian
$ source custodian/bin/activate
$ pip install c7n


First a policy file needs to be created in yaml format, as an example:

- name: remediate-extant-keys
  description: |
    Scan through all s3 buckets in an account and ensure all objects
    are encrypted (default to AES256).
  resource: s3
    - encrypt-keys

- name: ec2-require-non-public-and-encrypted-volumes
  resource: ec2
  description: |
    Provision a lambda and cloud watch event target
    that looks at all new instances and terminates those with
    unencrypted volumes.
    type: cloudtrail
        - RunInstances
    - type: ebs
      key: Encrypted
      value: false
    - terminate

- name: tag-compliance
  resource: ec2
    Schedule a resource that does not meet tag compliance policies
    to be stopped in four days.
    - State.Name: running
    - "tag:Environment": absent
    - "tag:AppId": absent
    - or:
      - "tag:OwnerContact": absent
      - "tag:DeptID": absent
    - type: mark-for-op
      op: stop
      days: 4

Given that, you can run cloud-custodian with:

# Validate the configuration (note this happens by default on run)
$ custodian validate -c policy.yml

# Dryrun on the policies (no actions executed) to see what resources
# match each policy.
$ custodian run --dryrun -c policy.yml -s out

# Run the policy
$ custodian run -c policy.yml -s out

Custodian supports a few other useful subcommands and options, including outputs to s3, cloud watch metrics, sts role assumption. Policies go together like lego bricks with actions and filters.

Consult the documentation for additional information, or reach out on gitter.

Get Involved

Mailing List -!forum/cloud-custodian

Gitter -


We welcome Your interest in Capital One’s Open Source Projects (the “Project”). Any Contributor to the Project must accept and sign an Agreement indicating agreement to the license terms below. Except for the license granted in this Agreement to Capital One and to recipients of software distributed by Capital One, You reserve all right, title, and interest in and to Your Contributions; this Agreement does not impact Your rights to use Your own Contributions for any other purpose

Download the Agreement

Code of Conduct

This project adheres to the Open Code of Conduct By participating, you are expected to honor this code.

Project details

Release history Release notifications | RSS feed

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

c7n-0.8.19.tar.gz (134.5 kB view hashes)

Uploaded Source

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page