Hello,

I have just installed Slackware 14.2 64 bits.
It is the first time I use a 64 bits operating system on my machine (I was always using a 32 bits operating system).

Also, I am using an UEFI (instead of a BIOS or an UEFI with the Legacy BIOS option enabled).

Also, I am using a GPT partition table (instead of a MBR).
I have used gdisk (instead of fdisk) in order to create my partitions:
* 100 MB for the UEFI partition
* 230 GB for the Windows 8.1 operating system
* 230 GB for the Slackware 14.2 operating system
* 005 GB for the Swap partition

I am using elilo (instead of lilo).

Well, it's fine but when I try to install Windows 8.1 32 bits I got the following message: "Windows cannot be installed on this disk. The Selected Disk is of the GPT Partition Style".

I thought it was because I forgot to disable the "Legacy BIOS" option in my UEFI but that's not the case: I have UEFI Only enabled.

So, I am wondering if Windows 8.1 does not recognize my 100 MB UEFI partition or maybe just does not support GPT.
According to Wikipedia, GPT is supported by Windows 8.1 32 bits.
I don't think I need the 64 bits version.

Have you any idea why I can't install Windows 8.1 after Slackware 14.2 has been installed with UEFI/GPT enabled?

Thank you.
Best regards.

From past experience with Windows, it is always best to install Windows first, then install Linux after. In the past, the Windows installer would always crap out if it didn't have control over the partitioning and if Linux partitions were present on the install drive. It's been quite a few years since I've dualbooted (last time was with Windows XP before Vista even came out), but, it seems like their installers haven't changed much over the years.

I agree, installing Windows first is the thing to do. This https://technet.microsoft.com/en-us/.../dn336946.aspx clearly states that you are correct, it ought to work. Something about your install media, bios/UEFI and GPT clearly isn't being recognized. It looks like you might be able to not reinstall everything if you use WinPE, but probably the easiest thing is to start from scratch.

Well, I have just tested with the 64 bits version of Windows and I have exactly the same behavior than with the 32 bits version.

So, I removed all the partitions from my disk with the Windows installer and I have installed Windows on the whole disk.
I let Windows partition my disk automatically.

After that, I will check with gdisk how is partitioned my disk.

It goes like this :

- A EFI partition formatted in FAT32
- A MSR partition (Microsoft System Reserved)
- The good ol' NTFS partition with your fresh Windows OS installed on it

I have exactly the setup you want to create. You need to make it like this:

- install Windows 8.1 first (no need to let it take whole disk, just set the size you want, leaving rest for Linux)
- after successfull Windows' installation you can install Slackware
- my tip is: don't waste space for swap partition; use swapfile instead
- and always remember that after kernel compilation you need to properly manage contents of /boot/efi/EFI

Working in such setup 3rd year already. Note, that if you're going to upgrade to Windows 10, it'll add one more partition, so you'll need to modify /etc/fstab accordingly after this.

I think I found something interesting that could explain why I need to install Windows first.
After I have installed Windows on the whole disk, I checked with gdisk the partition table.
I see a difference between the partition table when it is created by Windows automatically and the one that I have created with gdisk from the Slackware DVD.
The difference is that I have "MBR: MBR Only" instead of "MBR: protective MBR".

I don't know how it it possible with gdisk to get this result.
Each time I try to create a GPT partition table with gdisk, I got: "MBR: protective MBR".
I think that if I find the way to have "MBR: MBR Only" with gdisk, I will be able to use the Slackware DVD in order to partition my disk first, then I will install Windows on the partition I want without the "Windows cannot be installed on this disk. The Selected Disk is of the GPT Partition Style" message.

Do you know how to do that with gdisk?

Anyway, I don't understand exactly why with GPT, I can have MBR too because it is an other kind of partition table and I have always thought that only one sort of partition table can exist on my disk.
The gdisk utility tells me: "Found valid MBR and GPT. Which do you want to use?".
I guess that the correct answer is GPT because that's what I want.
I have the choice between:
* 1 - MBR
* 2 - GPT
* 3 - Create blank GPT

What do you suggest for this step?

Well, I guess that the correct choice is "1 - MBR".
Because if I select "2 - GPT" or "3 - Create blank GPT", then I print the list of partitions, it is empty.
However, if I select "1 - MBR", then I print the list of partitions, I see the two partitions:
* 350 MB NTFS (I guess it is the UEFI partition)
* 465 GB NTFS (I guess it is the Windows partition)

Can we say that Windows is using GPT whereas I need to choose MBR in order to list my partitions with gdisk?

Definitively, the answer to my last question is: "No".
Indeed, on Windows I do: Run > "diskmgmt.msc" > right click on my disk > Properties > Volumes.
What I see is: "Partition style: Master Boot Record (MBR)".
So, Windows is automatically using a MBR partition table instead of a GPT partition table when I install it on my disk.
That's so strange because I have an UEFI and its "UEFI Only" option is enabled.

How to force Windows to use GPT instead of MBR?

I found a way to do that.
I need to change a motherboard UEFI option.
Before: "Windows 8/10 Features" was set to "Other OS".
Now: "Windows 8/10 Features" is set to "Windows 8/10".

I have also increased the UEFI partition size from 100 MB to 500 MB but I am not sure if it helps to solve my problem.

Anyway, it works fine now: I can install Windows and Slackware together with UEFI/GPT:
* /dev/sda1 500 MB, FAT32, UEFI partition
* /dev/sda2 230 GB, NTFS, Windows partition
* /dev/sda3 230 GB, Ext4, Slackware partition
* /dev/sda4 005 GB, Swap, Swap partition

The only problem is: Where is my UEFI boot menu?
It boots directly to Slackware without prompting.

Just press F11, when that nice screen generated by your mobo's firmware shows up.

Pressing F11 is not something I want to do each time I reboot to change from an operating system to an other one.
Moreover, pressing F11 does not work with my GIGABYTE GA-H110M-S2H (rev. 1.0) motherboard.

But pressing F11 (or any other key like "q") during the ELILO loading let me on a prompt:
---
ELILO v3.16 for EFI/x86_64
.

ELILO boot:
---
I don't know what I can type here but if I press the Enter key, it loads the Slackware operating system.

I also found a way to boot on the Windows partition: press ESC (or DEL) to enter Setup > go to the Power Management tab > go to the Boot Override section > select the Windows Boot Manager item.

Anyway, as I said, pressing a key at startup is not what I want.

ELILO does not provide a boot menu?
What about GRUB?

For a boot manager you might want to try rEFInd. It's available via Slackbuild.org

Your question was: "Where is my UEFI boot menu?" - so I assure you, there's no other way to enter UEFI boot menu than by pressing F11.
Any other boot menu (if possible at all) no longer is "UEFI boot menu".

I believe on a Gigabyte motherboard the correct key to get the UEFI Boot Menu is F12, but again if you don't want press any key, then give rEFInd a try.

cRubbish. That merely gains access to the vendor provided UI.
The EFI variables are available to Linux - how they are presented to the user is the authors decision; have a look at efibootmgr. Grub can certainly display such as well as others. If one is sufficiently masochistic, you an directly run the EFI shell yourself.

I repeat: the original question was about "UEFI boot menu" - not about menu provided by GRUB, neither by any other "3rd party boot manager". It is always recommended to read with comprehension. BTW: efibootmgr, from what I see (not using it by myself) won't provide boot menu ("It is a popular tool for manipulating the EFI settings in order to create and manage boot entries capable of booting Linux (or any other EFI operating system)").

To install Windows and Slackware with UEFI I had to create a bootable UEFI USB drive and boot from it. I could not get Windows to create a UEFI installation from the supplied DVD's. Same thing with Slackware. The key point seemed to to be I had to boot from a UEFI enable USB drive. I also noticed I had to run my motherboard setup with the UEFI drive inserted, before my motherboard (Gigabyte) would recognize the drive.

My steps:
Create a UEFI enabled USB drive with Windows.
Boot the drive and let Windows take the whole disk.
Shrink Windows.
Create a UEFI enable USB drive for Slackware.
Boot and install Slackware.

HTH.

-JJ

PS here is my partition layout:

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