How can I reinstall Windows 10 without erasing Ubuntu?

Question

I have a computer with both Ubuntu 18.04 and Windows 10 installed. I would like to reinstall windows but without erasing Ubuntu.

How can I do that? Are the ext3 partitions used by Ubuntu?

Answer 1

ext2, ext3 and ext4 partitions should only be accessed by Linux operating systems, such as Ubuntu. There are drivers out there, both Open Source and commercial, which claim to allow Windows to access ext partitions, but many, many people here report problems with them.

Before reinstalling Windows, please make a complete backup of your system, then verify the backup to make sure it matches the source files; then backup again to a different target disk or to the cloud, and verify that backup.

Then, you can proceed with a reinstallation of Windows. Windows is much better about not overwriting GRUB than it used to be, but you may need to repair GRUB following How can I repair grub? (How to get Ubuntu back after installing Windows?)