As noted in our quarterly update (https://cloud.gov/updates/2019-02-26-quarterly-update/
), we are changing the default "stack" for your applications from cflinuxfs2 (Ubuntu 14.04, which has reached end-of-life) to cflinuxfs3 (Ubuntu 18.04) during this window. Unless you specify otherwise (in your application manifest or using a command-line parameter), your application will deploy using cflinuxfs3 from here out.
If you run into problems, you can explicitly specify cflinuxfs2 to stay with cflinuxfs2. However, be forewarned that cflinuxfs2 will be going away at the end of April, so this is only a temporary solution! You should work out any issues with cflinuxfs3 as soon as possible.
For more information, refer to the details in our quarterly update.