Dual booting Win8.1 & Ubuntu MATE specific problem

Question

So today I was going to install Ubuntu MATE 15.10

I've got an Acer Aspire E1-572G type laptop. There's already a copy of Windows 8.1 on it.

The problem: After installing, I can't boot into Ubuntu at all, from nowhere. Here are the details which went down:

Win8.1 is on a 400GB partition of a 1TB HDD, the other ~600GB is free space. I made a bootable USB out of the Ubuntu MATE .iso, fat32. In Legacy mode, NOT UEFI I've booted it up, went right into the installation of Ubuntu. There I've made partitions according to this: How to use manual partitioning during installation?

In the end I've ended up with 11 partitions or so, at least the last /dev/sda was /sda11. The Ubuntu MATE installation went on sda7.

I've done everything as it is written in the article, but when rebooting after installation the computer booted up in Win8.1. Alright, I had this problem once with Kali Linux, there I've downloaded rEFInd, made a live USB from it and it seamlessly worked fine from there (I could only use it with the pendrive at my hand - but that makes Kali even more interesting doesn't it? :P) So I thought at first this would be the solution here as well. So when it booted into rEFInd it couldn't detect Ubuntu MATE, only Win8.1. So I've googled this problem.

First I went into the Live USB to select "Try Ubuntu MATE" and download boot-repair there successfully. However, before boot-repair could just fix the problem it exited with the error "boot-repair needs an EFI environment so it can't do shit right now". Then I tried to install grub2 again on sda7, it said it was successfull at the end but the result didn't show this.

Second I changed Legacy bootmode to UEFI. It still got me straight into windows after boot, so I tried the Ubuntu Live USB I've used at the installation. It couldn't boot because of Security concerns. Headed to the next helping article, it suggested me to turn off secure boot. Well this wasn't easy on an Acer laptop (it is different than on a regular PC or laptop...) but ultimately I could turn it off. So now I've tried again the Live USB.

Not a huge success. Now the error is "System doesn't have any Bootable USB device". Then I tried this from going to "Update and recovery" in win8.1 and selecting the Bootable USB option but it was the same error.

Anyways, I've found at most places that the problem is that Windows is installed in uefi mode while linux is installed in legacy bios mode. But the solutions I've found online I couldn't apply because they both rely on either successfully booting up the Live USB or changing the boot mode to CSM which is also not an option for me.

So here I am 4 hours after putting all the necessary Ubuntu MATE files on my hdd and I can't use it as of yet. I hope someone could help me, I'd be really grateful. My Google search statistics are like 9000 searches/hour so you can imagine I did try out every method, every solution there was available. Being desperate here so please don't judge me. I've never posted anything on help forums because I could solve anything by googleing it until today...

SORRY FOR THE LONG READ

Answer 1

I made a bootable USB out of the Ubuntu MATE .iso, fat32. In Legacy mode, NOT UEFI

This was your first (and only really major) mistake. Rule Number One in modern dual-booting is to install all your OSes in the same boot mode (BIOS/CSM/legacy or EFI/UEFI). Mixing boot modes is possible, but requires extra hoop-jumping and knowledge of how the pieces all fit together.

A lot of guides recommend enabling the BIOS/CSM/legacy support as a routine part of installing Linux. This is a Bad Idea. For details on why, see my Web page on the subject. Enabling this support can indeed clear certain initial hurdles, but at the cost of creating bigger ones down the road. It's better to figure out what's causing the initial hurdle. These days, it's usually an improperly-prepared USB disk image, or sometimes Secure Boot problems.

So when it booted into rEFInd it couldn't detect Ubuntu MATE, only Win8.1.

rEFInd should have detected an installed Ubuntu. The fact that it didn't makes me think that something may be more seriously wrong with your installation, but I can't be sure of that. I recommend you boot to an Ubuntu live disk and run Boot Info Script. This will create a file called RESULTS.txt with details on your configuration. Post it to a pastebin site and post the URL to your document here so that others can analyze it.

Actually, another thought occurs to me: What filesystem(s) did you use for Ubuntu? rEFInd supports ext2/3/4fs, ReiserFS, and Btrfs; but if you used JFS, XFS, or something more exotic rEFInd won't be able to find your kernel. You might be able to work around this problem by adding an EFI driver for your filesystem from the efifs drivers project. Also, if you used Btrfs, there are special additions to rEFInd's scanning options required in some cases. These are mentioned briefly on the rEFInd drivers page.

I tried the Ubuntu Live USB I've used at the installation. It couldn't boot because of Security concerns.

Could you please post the EXACT error message? (A digital photo may be helpful.) If you booted a stock rEFInd image, Secure Boot should not be an issue, since the standard rEFInd CD-R and USB flash drive images don't support it. OTOH, if you modified these with Shim or PreLoader, you could have gotten in. ALT Linux, and perhaps one or two others, also use rEFInd with Shim or PreLoader, so if you used one of them, you might have gotten into rEFInd with Secure Boot active.

Also, if you get into rEFInd, it might be able to launch the Ubuntu installer on another USB drive. (You might need to hit Esc in rEFInd to re-scan devices to get the USB devices to show up.)

Now the error is "System doesn't have any Bootable USB device"

The exact context of this message could be important. Is this a message from the firmware, from GRUB, or something else? Again, a screen shot showing context may help.

One more point: Some utilities for creating bootable USB devices don't write EFI boot loaders. Unetbootin and Rufus generally do a good job at this. If yours lacks the EFI boot loader, you might see a message like this. (This problem is one of those that's easier to overcome than the problems of a mixed-mode installation.)

Answer 2

Well, installing Ubuntu alongside Windows 8(and over) is very easy. You shouldn't have gone for the "Something Else" option as "Install Ubuntu alongside Windows" was available and Ubuntu Mate 15.10 has many resolved issues. If you can, delete all those partitions you created, and restore the 600GB of space to Windows. When Windows has the 1TB back and there is no extra space for anything else but Windows, restart and boot the USB with Ubuntu installed. Choose "Install Ubuntu alongside Windows 8".

On the next screen, select how much space you want to allocate Ubuntu then follow the prompts.

More info here.