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Upgrading App to cflinuxfs4 Important Update

April 27, 2023

Deprecation of cflinuxfs3

Ubuntu 22.04 stack (cflinuxfs4) buildpacks are here and Ubuntu 18.04 (cflinuxfs3) are retiring: upgrade your apps now!

The base OS image used by your applications is called a “stack”. The stack we’ve provided to date is called cflinuxfs3, and it’s based on Ubuntu 18.04 LTS, released originally in mid 2018 with continuous security updates since then. cflinuxfs4 is a new OS image based on Ubuntu 22.04 LTS, and is now default stack in Ubuntu 18.04 will likely no longer receive security updates in May, so we will stop supporting cflinuxfs3 in May 10th.

Who is impacted?

If you push your Cloud Foundry applications as Docker containers with cf push --docker-image , these changes do not impact you.

However, most customers deploy their applications using buildpacks, and their apps don’t have any dependency on the particular OS version that runs them. If that describes you and you have existing applications running on, this upgrade will impact you and you’ll need to update the stack on your applications.

What should you do now for existing apps?

For existing applications which were created under cflinuxfs3 you will need to update the stack declaration to cflinuxfs4, there are two common ways of doing this detailed below. The options below only have to be run once for each application on cflinuxfs3, once the stack is set for an application, it is persistent until changed with any of these two steps.

  1. Push the app manually and specify the stack with the cf cli:

    cf push MY-APP -s cflinuxfs4
  2. Use the stack-auditor cf cli plugin to change the stack without having to push the application. Documentation for using this plugin is at, the basic workflow is:

    • Install the plugin
    • Use the cf cli to target the org and space for your existing application
    • Run cf change-stack APP-NAME cflinuxfs4 to change the app to the cflinuxfs4 stack

    Each application will take about a minute or so to run the cf change-stack... command depending on the size of the droplet.

What should you do now for new apps?

For any new applications, simply run a cf push to pick up the new cflinuxfs4 stack:

cf push MY-APP


When What Available Stacks Default Stack
March 23 Roll out all cflinuxfs4 buildpacks cflinuxfs3, cflinuxfs4 cflinuxfs3
March 23 - April 27 Developers test and update apps to use cflinuxfs4 cflinuxfs3, cflinuxfs4 cflinuxfs3
April 27 Support ends for cflinuxfs3. All new apps pushed will use cflinuxfs4 by default, existing apps will need to be migrated. cflinuxfs3, cflinuxfs4 cflinuxfs4
April 27 - June 29 Explicitly opt to use cflinuxfs3 if you need more time cflinuxfs3, cflinuxfs4 cflinuxfs4
June 29 cflinuxfs3 buildpacks will be retired from the platform, apps needing cflinuxfs3 buildpacks will need to reference them via URL on the cf push cflinuxfs3, cflinuxfs4 cflinuxfs4
Sept 28 Only cflinuxfs4 will be available, this is a breaking change for apps not updated to use cflinuxfs4 cflinuxfs4 cflinuxfs4

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