GitHub Actions: Ubuntu-latest workflows will use Ubuntu-20.04

Workflows using the ubuntu-latest runner label will soon run on Ubuntu-20.04. GitHub Actions has supported Ubuntu-20.04 in preview mode since June 2. During these past four months we have monitored image stability and customer feedback, and waited for a range of critical software tools to improve support for Ubuntu-20.04.

Now Ubuntu-20.04 is ready to be the default version for the ubuntu-latest label in GitHub Actions workflows. This change will be rolled out over a period of several weeks beginning on November 30, 2020.

If you see any issues with your workflows when they are transitioned to Ubuntu-20.04:

• File an issue in the virtual-environments repository
• Switch back to Ubuntu 18.04 by specifying the ubuntu-18.04 runner label. We will continue to support Ubuntu 18.04.

Note that image software between Ubuntu-18.04 and Ubuntu-20.04 differs by the pre-installed and default versions versions of some tools. See the full list of changed software.