Install media sometimes fail media check at 4.8%

Problem

After creating a USB installation medium and trying to boot it, the included “media check” started during boot might report an error at 4.8% and announce that the media is corrupt and shouldn’t be used, even though the media might be technically just fine.

Generally, when seeing this image, you can be fairly sure that the image is really corrupt and you should verify the checksum of the downloaded image (if you downloaded it manually) and try to create the USB medium again (ideally using a different thumb drive).

However, when you see the failure at 4.8% specifically, it might be a false negative. The installation medium might be fine.

This problem might happen when creating the install media on any operating system using any tool, but recently has been mostly reported by Windows users using Fedora Media Writer.

You can discuss this issue here.

Cause

The cause is unclear. The current theory is that when the image is (correctly) created, and after it passes the verification performed by Fedora Media Writer, the operating system automatically mounts one of the partitions, which then changes the filesystem metadata slightly. This has no adverse effect on performing the installation (all the data are intact), but it changes the media checksum, which then fails verification.

Related Issues

Bugzilla report: #2269373
Upstream FMW report: #669

Workarounds

Always verify the checksum of the downloaded image (unless it was downloaded for you by Fedora Media Writer). Try to create the USB installation medium multiple times, ideally using different USB drives. During the creation, make sure to close all applications that could try to touch the newly created partitions (file browsers, disk management tools, etc). After the writing is complete, unplug it from the computer, and plug it to a powered off computer just before attempting to boot from the USB drive.

If all your attempts still fail with the media check error at 4.8% specifically, you can skip the media check in the medium boot menu by selecting “Start Fedora…” option instead of the default “Test this media & Start Fedora…” option. If the installation image starts fine and everything looks functional, hopefully the image is not corrupt, and you’ve just stumbled on this problem as described here. Perform the installation.