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Revision as of 22:29, 15 October 2022 by Ngompa (talk | contribs) (→‎Scope: Add backport dmsquash-live-autooverlay step)

Modernize Live Media

This is a proposed Change for Fedora Linux.
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.

Summary

Modernize the live media by switching to the "new" live environment setup scripts provided by livesys-scripts and leverage new functionality in dracut to enable support for automatically enabling persistent overlays when flashed to USB sticks.

Owner


Current status

  • Targeted release: Fedora Linux 38
  • Last updated: 2022-10-15
  • FESCo issue: <will be assigned by the Wrangler>
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

As part of preparing to change our tooling around producing images, we need to update the way we produce working live media. This has been done in two parts: the live environment setup scripts have been reworked to run properly through systemd and are packaged in livesys-scripts and new functionality in dracut has been added to enable support for automatically enabling persistent overlays when flashed to USB sticks so that livecd-iso-to-disk.sh can be retired.

Feedback

Benefit to Fedora

Since we introduced live media in Fedora Linux 7, the actual mechanism in which the live environment sets itself up has been complex and intricately tied to the method in which we produce the media (using Kickstarts). The nature of the implementation of those scripts means that they are hard to understand and debug, which has caused problems in the past whenever we've needed to update them.

As we look forward to new and better tooling for producing images (such as kiwi and osbuild), we cannot continue to rely on kickstart-driven image builds that construct shell scripts on the fly to embed in the image as we do now. With livesys-scripts, those scripts have been simplified and turned into systemd services that activate only in live environments.

This also gives us the opportunity to introduce new functionality for live media. New functionality was added to dracut and backported to Fedora so that we can retire the remaining usage of livecd-iso-to-disk.sh and provide a better experience with our live media, particularly for portable backup and rescue environments by introducing the ability to automatically setup persistence on boot when unpartitioned space is detected on a USB stick on boot.

Scope

  • Other developers:
    • Anaconda may need adaptations to correctly filter out more live environment specific boot arguments when configuring the installed environment.
  • Policies and guidelines: N/A (not needed for this Change)
  • Trademark approval: N/A (not needed for this Change)
  • Alignment with Objectives: N/A

Upgrade/compatibility impact

There should be no impact here, as this affects only the live environment.

How To Test

Once the changes are merged, simply try to boot produced live media.

There should be new options for resetting the persistent overlay and booting with no persistence. The default options should boot with persistence and setup of persistence should work.

Testing persistence behavior is simple: 1. Boot normally 2. Create a file in the home directory 3. Reboot into the environment 4. See the file is there still

Testing the reset behavior would go similar to the regular test, except you should expect the file to not show up in step 4. Same for booting with no persistence.

Otherwise, the media should work like before, and things like live installation should work as expected.

User Experience

When booting live media, two new menu options will become available: one to reset the persistent overlay while booting, and one to boot without persistence. The default boot options will create a persistent overlay if it doesn't exist and can be written (e.g. when booting from a USB stick).

Dependencies

Contingency Plan

  • Contingency mechanism: Revert changes to fedora-kickstarts and lorax to go back to previous behavior
  • Contingency deadline: Final Freeze
  • Blocks release? Yes


Documentation

Information on the persistent overlay functionality is included in the Dracut documentation.

Release Notes

By default, Fedora Linux live environments flashed to writable USB media with sufficient free space will maintain user changes to the environment. This "persistence" can be reset at boot time through the boot menu.

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