Changing Stacks

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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 applications running in compartments. Under Diego architecture, cell VMs can support multiple stacks.

Note: Docker apps do not use stacks.

Available Stacks

The Linux cflinuxfs2 stack is derived from Ubuntu Trusty 14.04. Refer to the Github stacks page for supported libraries.

Restaging Applications 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 Elastic Runtime. 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 as follows:

  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
    name            description
    cflinuxfs2      Cloud Foundry Linux-based file system
  2. To change your stack and restage your application, use the cf push command. For example, to restage your app on the default stack cflinuxfs2 you can run cf push MY-APP:

    $ cf push MY-APP
    Using stack cflinuxfs2...
    Creating app MY-APP in org MY-ORG / space development as
    requested state: started
    instances: 1/1
    usage: 1G x 1 instances
    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

    To specify a different stack, append -s STACKNAME to the command.

Stacks API

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

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