Changing Stacks

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This topic explains how to restage apps on a new stack. It also provides a description of stacks and lists the supported stacks on Pivotal Web Services (PWS).

Overview

A stack is a prebuilt root file system (rootfs) that supports a specific operating system. For example, Linux-based systems need /usr and /bin directories at their root. The stack works in tandem with a buildpack to support apps running in compartments. Under Diego architecture, cell VMs can support multiple stacks.

Note: Docker apps do not use stacks.

Available Stacks

PWS includes support for cflinuxfs3. The Linux cflinuxfs3 stack is derived from Ubuntu Bionic 18.04. For more information about supported libraries, see the GitHub stacks page.

Restaging Apps on a New Stack

For security, stacks receive regular updates to address Common Vulnerabilities and Exposures (CVEs). Apps pick up on these stack changes through new releases of PWS. However, if your app links statically to a library provided in the rootfs, you may have to manually restage it to pick up the changes.

It can be difficult to know what libraries an app statically links to, and it depends on the languages you are using. One example is an app that uses a Ruby or Python binary, and links out to part of the C standard library. If the C library requires an update, you may need to recompile the app and restage it.

To restage an app on a new stack, do the following:

  1. Use the cf stacks command to list the stacks available in a deployment.

    $ cf stacks
    Getting stacks in org MY-ORG / space development as developer@example.com...
    OK
    
    name            description
    cflinuxfs2      Cloud Foundry Linux-based filesystem - Ubuntu Trusty 14.04 LTS
    cflinuxfs3      Cloud Foundry Linux-based filesystem - Ubuntu Bionic 18.04 LTS
    
  2. To change your stack and restage your app, run the following command:

    cf push MY-APP -s STACK-NAME
    

    Where:

    • MY-APP is the name of the app.
    • STACK-NAME is the name of the new stack.

    For example, to restage your app on the stack cflinuxfs3, run cf push MY-APP -s cflinuxfs3:

        $ cf push MY-APP -s cflinuxfs3
        Using stack cflinuxfs3...
        OK
        Creating app MY-APP in org MY-ORG / space development as developer@example.com...
        OK
        ...
        requested state: started
        instances: 1/1
        usage: 1G x 1 instances
        urls: MY-APP.cfapps.io
        last uploaded: Wed Apr 8 23:40:57 UTC 2015
            state    since                    cpu    memory        disk
        #0  running  2015-04-08 04:41:54 PM   0.0%   57.3M of 1G   128.8M of 1G
        

Stacks API

For API information, see the Stacks section of the Cloud Foundry API Documentation.

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