Upgrading my Linux-Windows multi-boot system to Windows 10

Will upgrading Windows 7 or 8.1 in-place to Windows 10 cause problems on a multi-boot system which boots Linux by default? I'm going to find out.
Written by J.A. Watson, Contributor

It's been a while, but like a bad penny, I just keep coming back. And while I was away, Windows 10 was released for general distribution - and free updates of Windows 7 and Windows 8 systems.

I'm sure that I was not the only one who started wondering what the impact of upgrading a multi-boot Linux/Windows system would be, but unlike many others, I have several such laptops and netbooks on which I could actually try the upgrade, and if things went wrong I wouldn't be worried by whatever negative consequences. In the worst case (best case? most extreme case?) I could simply wipe Windows from the system and leave it as Linux-only.

So, after having the nuisance "Get Windows 10" icon on the system tray for six months or so, it was finally time to let it try to do something. The first system I tried was my Acer Aspire E5-111, which is a reasonably well configured subnotebook. To get an overview of the hardware and what I had installed on it, check this previous post, written when I first set it up.

In a nutshell, this is a UEFI firmware system, loaded and configured to boot openSuSE 13.2 via grub-efi, and with a number of other Linux installations and Windows 8.1 available from the GRUB boot menu.

Please note: I had one huge advantage in testing on this system, which those who might want to try the same thing should consider carefully. Although this is the system which I carry in my backpack, and use most frequently, I don't have anything permanently stored on it which is not also on one of my other computers.

I also have no qualms about wiping a system clean and completely reinstalling everything from scratch.

If you are not as fortunate/flexible as I am, then please make sure that you have complete backups of both the Linux and Windows systems before attempting this upgrade.

The first step was to click on the nuisance icon, and tell it that I wanted to upgrade. It then told me that the upgrade would be downloaded and prepared, and I would be notified when it was ready to install. That could be a few hours, days or weeks. Until such time as it is ready to install, there is no further indication that it is actually doing anything, or how much has been done or is left to do, or how longer it might be. After looking around on the net a little, I found that the necessary files are downloaded to a hidden directory at the top of C:, so you can check that to see how it is doing - it needs to download some 6+ GB to that directory.

Of course, this downloading happens in the background, which means that you have to leave the system running Windows for quite a while. That's a minor inconvenience for me, since I seldom boot Windows. I finally decided to just start Windows and then set the laptop aside until it was done downloading, and I took a different system for my normal work. That is not actually necessary, I assume that if you continue to use the computer while it is preparing for the update, the download and preparation will simply take somewhat longer.

Once everything has been downloaded, and whatever other preparations are necessary had been completed, I got a notice (from the nuisance icon) that Windows 10 was ready to install. I clicked through that, and got a typical sequence of "we are not responsible if this upgrade destroys your computer or ruins your day" warnings, then it finally said to "sit back and relax" while the upgrade installed.

The upgrade process took about two hours, and included several reboots. At the end there is a rather long series of screens with privacy and configuration questions. A lot of questions, all of which pretty much boiled down to "do you want to send XXXXX information to Microsoft". I urge you in the strongest terms to read these questions carefully, consider what they really mean, and be careful with your answers. There was ONE which I said "yes" to, and I wavered on that one for quite a while.

The first and most obvious effect of the upgrade installation was that Windows 10 had made itself the default boot object. I consider that to be rather rude, but unfortunately it is getting to be more common - in fact, Ubuntu now does it during routine updates pretty frequently, as well. However, when I went to reset the UEFI boot order, I found that Windows had not only put itself first in the list, it had actually removed all of the other entries. Ugh. That's a bit worse than just rude...

I had a brief moment of concern at this point, when I thought perhaps Windows had not only cleared the boot list but also cleared the disk, but when I booted an openSuSE Live image, and checked the disk partitioning, I saw that it was all still ok. It took a bit of work with the efibootmgr utility to rebuild the boot list. If you need some information and details about how to do this, please read my previous post about UEFI Boot Problem Solving. It's actually not a terribly difficult thing to do.

So, once I had the boot configuration repaired, I let it boot openSuSE and everything looked just fine. There's even a bit of good news from the Linux side, actually, because the basic disk layout and configuration for EFI boot of Windows 10 is still the same as it was for Windows 8, so nothing needs to be modified in the grub-efi configuration files. I went quickly through the other Linux installations on that system (Fedora, Manjaro, Debian, Mint, LMDE, Ubuntu), and none of them had any problems. They all were able to rebuild their grub boot configuration files with Windows 10 included.

There is one more comment/caution that I need to add before closing this post. I have said many times before, UEFI firmware implementations vary wildly between manufacturers. I actually quit buying HP systems (and got rid of the ones I already had) because getting the UEFI firmware configuration to be right, and stay right, with Linux multi-boot was just too much trouble. I did this first upgrade on an Acer Aspire system, and it has one of the best UEFI firmware implementations I have seen - and I didn't have much trouble with it. But it is still possible that a system from another vendor might have a lot more difficulty.

If you decide to try this, or have already tried it either successfully or not, feel free to share your experience in the comments.

Oh, one last thing. Please don't write and ask me what I think about Windows 10. I don't use it, I haven't tried it any more than superficially, and the only opinion I have is extremely biased. I keep Windows loaded on some of my laptops because I frequently loan them out, give them away, or otherwise pass them on to be used by friends and family who need them, and those people sometime prefer Windows to Linux.

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