linuxmemes

Not sure why, but your comment made me think about the first machine I switched to Linux. It was a laptop who's fan eventually had a bad bearing and needed to be replaced. Luckily it was still under warranty, so I sent the laptop in to get the fan replaced, and received my laptop back with Windows installed on it... I was so livid.

That's the way to go

Grub does not do the same thing unless something has gone wrong. It detects windows and offers you the choice on boot as to which OS to start.

Not the case. What's happening here is Windows is removing the ext4 partition completely, expanding the ntfs partition and writing to all of it.

Windows update did that to my <1 year old laptop. I figured it had just wiped out grub, but when it was booted from a live-usb there was no ext4 partition there at all. This has been reported many times.

Microsoft should be sued for this shit. Legal protection from destroying people's data that is not part of Windows or in a Windows partition, whether deliberately or by negligence, is not something that can be legitimately covered by a license agreement.

In my experience (W11 + Fedora on UEFI Thinkpad), I've seen it actually get rid of the Fedora entry from the UEFI boot list. Reinstalling GRUB from chroot didn't fix it, so I used EasyUEFI and manually added the Fedora EFI file to the boot list and that worked.

So it wasn't simply changing the boot order, it actually nuked Fedora from the UEFI boot list.

It sometimes destroys the Linux boot sector too. But it's simple enough to chroot with a live usb and repair it. I don't even have both OS as an option. Mine boots straight into Linux unless I interrupt it and use the boot another drive option. Linux and Windows have their own separate boot sectors, but Windows will fubar the Linux sector randomly.

They still need to share an EFI partition

My guess: the windows update fucked up Grub. Happened to me once or twice in 20 years of dual booting. It is also easily recoverable.

It tends to happen if you are not using the windows bootloader (GRUB for example) but if you use the windows bootloader it should be fine

I'd argue one shouldn't even be messing with dual booting if they don't understand much about the bootloader.

Windows: "Let me repair Linux for you"

If you install Linux first and then Windows on the same drive, it will fuck up your bootloader.

You can easily make Grub boot Windows, so just overwrite whatever fuckup Windows made, or install Windows first.

It won't happen with a simple update, though, that's for sure. Maybe if you're upgrading Windows to a new major release.

I unplug physicals disks when installing windows. Learned the hard way when windows placed the boot partition on a device it could not detect the filsystem of. It destroyed my RAID disks (a little but my fault, because I messed up the recovery).

This is what Windows installer saw (going by memory, this was 8 years ago)

• SSD 500 GB (either it recognised ext4 file system, or this one was unknown)
• SSD 500 GB (Where I specified to install windows)
• 4 x HDD 8TB (unknown disks, unknown file system, Windows unaware that this was a RAID-5 software dm-raid)

What did it to? It created a new partition table and wrote data to a new boot partition it made on one of the 8TB disks, no questions asked.

So, to the people who answered you that windows installer cannot do this. Maybe they fixed it. But it certainly could, and it cetianly did. I remember very carefully going through the installer because I was concerned about this happening. I thought about unplugging them, but was lazy. Because "it would be insane for windows to write on a disk it cannot identify the file system of".

Lessons learned:

• If you plan to install windows on a disk along side Linux, install windows first, if you can. Safest bet is still to:
• If you cannot, unplug all other disks other than the one windows is intended to be on.

Edit: I found post on this way back when, but leaving what I wrote as is.

https://superuser.com/questions/758854/mdadm-win7-install-created-a-boot-partition-on-one-of-my-raid6-drives-how-to-r#1243636

I had remembered some details wrong. I had unplugged the Linux SSD, and it wad raid 6 not 5, and it was 2TB disks.

Whoa.. this really happens?

No, the only thing that windows might do, is reset the bootloader so it skips grub. If you're using UEFI (which you should), you can easily restore it from your bios.

I've only seen it happen on big updates, not the smaller ones.

But it knows there's a partition there and it's easy to know it's a Linux partition type. Microsoft just prefer to say it doesn't know the partition type and simply say it ignores it. You don't need to have support for a file system in order to check it's partition type. It's just ms bs