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Dual Boot Windows 10 with UEFI


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#1 pcpunk

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Posted 25 June 2018 - 10:38 PM

I'm trying to fully understand how to Dual Boot Windows 10 with UEFI before I jump into my next project.  Windows 10 has been installed in UEFI and GPT and Fast Boot Disabled from within Windows 10.  I was hoping some of you would share the best Tutorials you know of.  I'm also struggling with where to install "Boot Loader Device" I see Tutorials but some doing it a little different.

 

I don't need to know the basics of creating partitions and such, just the UEFI part of it all as this is my first with UEFI.

 

It seems as though most tutorials are installing "Boot Loader Device" to /dev/sda, shutting down and booting a Linux Live Session, and then using "sudo efibootmgr" command to see what the order and boot numbers are.  Then changing the boot order with "sudo efibootmgr --bootorder xxxx,xxxx" then Restarting and hoping for the best.

 

So what is happening here, where is grub being installed?

 

1. INSTALLING MINT KDE 17.3

 

2. I ALREADY DISABLED FAST BOOT, BUT FROM WITHIN, AND NOT FROM BIOS.

 

3. DO I NEED TO INSTALL BOOTLOADER TO EFI PARTITION OR /dev/sda?
a. IT SEEMS AS THOUGH THIS IS AUTOMATIC WHEN IN EFI MODE AS SEEN IN THE OFFICIAL UBUNTU UEFI DOCUMENTATION?
 
4. DO I NEED TO BOOT FROM “ADVANCED OPTIONS” OR JUST USE ONE OF THE FUNCTION KEYS?
 
5. HOW TO BE SURE I’M INSTALLING IN UEFI?
a. I ALWAYS BOOT FROM DVD TO BE SAFE, BUT I ASSUME THAT BECAUSE WINDOWS 10 IS ALREADY INSTALLED IN EFI MODE IT WILL BE FINE.  OR CREATE A USB AS GPT, WHICH I WON'T BECAUSE IT IS EASIER TO JUST USE A DVD.
 
6. SOME SITES ALSO SUGGEST TO DISABLE SECURE BOOT, BUT AS I UNDERSTAND IT THIS IS NOT NEEDED.  I'VE BOOTED PLENTY TIMES FROM A UEFI MACHINE WITH SECURE BOOT ENABLED, WITH A DVD, OR USB CREATED AS GPT.
a. IF IT IS REQUIRED DO I RE-ENABLE IT WHEN DONE?
 
This Official Ubuntu UEFI Guide has actually answered a few of my questions but I will leave them anyhow in case someone has something good to add.
 
This is a good one I think NickAu has linked us to a few times:
 
This one says to Disable Secure Boot:
 
This one claims that the Boot fix can be done from within Windows:
 
Thanks, pcpunk...good night
 
 
 

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#2 NickAu

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Posted 26 June 2018 - 12:35 AM

 

This is a good one I think NickAu has linked us to a few times:

When using this method make sure you follow all the instructions especially the last bit Change The Boot Order So That Ubuntu Can Boot, using efibootmgr, This must be done from the live session.



#3 Gary R

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Posted 26 June 2018 - 03:37 AM

The 2 main things to be aware of when installing with UEFI and GPT are ....

 

  1. Secure Boot ... to prevent the installation of "bootkit" infections on Windows machines, UEFI enables pre-boot checks of OSs to be made. Basically it will check the OS that is to be loaded against a number of "approved" OSs held in firmware, and only if the OS passes the check, will it be allowed to load. Because of this, some Linux distros will require you to disable Secure Boot in order for them to load. Ubuntu (and most of its derivatives) are "approved" so it's generally not necessary to disable Secure Boot if you're using those.
  2. Fast Boot ... if Fast Boot is enabled, the computer does not fully shut down when you end a session, and therefore the boot loader is not accessed at boot up (the next time you boot), so if you have a dual boot machine, you will only be able to access the OS you were using in your last session. To prevent this, you need to disable Fast Boot.

Other than that, as far as I'm aware, booting Using UEFI is not really much different than booting using MBR.

 

 

 



#4 MadmanRB

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Posted 26 June 2018 - 02:39 PM

Here is what i do for my GPT/EFI machines:

 

When on the linux live I open up gparted, while yes the automatic setting in most installers is okay I usually make sure that linux never ever overwrites or alters the windows 10 efi partition.

I shrink windows down to use half of the drive then for the remaining I create three partitions for linux.

One a fat32 partition so that linux can have its own efi partition, a /boot partition and them root (as I use a SSD I devote another disk to /home)

I have got into the practice of using a separate boot and home partition and trust me its for the best, windows at any time can remove the linux bootloader at any given time.

By devoting another partition to boot on linux i save myself any issues.

I suggest learning how to partition if you have not done so already, its really a handy skill to have in the post efi world.


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#5 pcpunk

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Posted 26 June 2018 - 04:20 PM

 

One a fat32 partition so that linux can have its own efi partition, a /boot partition and then root (as I use a SSD I devote another disk to /home)

Can you clarify this MadmanRB.  Or line me out on what, why, when and where so to speak?

 

Do you mean the fat32 will be the /boot Partition?  Either way, what Bootloader Device would you install grub on.  The fat32 or /boot, or /dev/sda?

 

You would to it like this:

 

-fat32

-/boot

-/root

-/home

 

What would happen if one installed grub to the windows efi partition as I've read at least once of people doing.


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#6 MadmanRB

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Posted 26 June 2018 - 09:52 PM

Okay let me clarify:

 

The first partition I create in linux is the efi/FAT partition, this is where the efi bootloader (if any) is installed

This partition is actually optional as I use it for distros that dont have a official EFI sign key such as manjaro.

This efi parituion is its own partition, you could do without it but I never over write the windows efi partition or assign the installer to put the boot file for linux there.

With so many issues facing windows overwriting the efi partition so that only it boots this does seem like a very good step to make.

Even for say Mint or ubuntu this is a good idea, never know when windows will overwrite the efi and just list windows on it.

Next is a separate /boot partition, this is dfferent than the efi partition.

Both this machine and my older machine (Codename Littlemissbliss) both offer a dual BIOS mode

Meaning both legacy and UEFI are supported, to ensure full compatibility this is why /boot is its own partition.

Again this is something that ubuntu or mint do not do, they have everything under one partition and with windows being the way it is and me being a chronic distro hopper I have made this a option, this ensure no matter the distro i have a fallback if windows mucks up my bootloader.

Then comes root /

Then Home

 

I always ensure my bootloaders install (underr mint or ubuntu) install under /boot and as for Manjaro it offers both.

I can alwaysd switch between legacy and uefi this way if things go wonky.

I used a similar tactic on my old now dead laptop, its bootloader was a pain

 

as for installing GRUB under the windows efi drive, dont do it.

This can make windows unbootable or make windows overwrite the linux bootloader.


Edited by MadmanRB, 26 June 2018 - 09:55 PM.

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#7 pcpunk

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Posted 26 June 2018 - 10:33 PM

Can someone explain what is going on with efi and grub? 

 

Is Linux Overwriting/Rewriting the efi partition and adding it's Linux entries?  Will I see Grub on boot doing it the way in the Link NickAu provided?


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#8 MadmanRB

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Posted 26 June 2018 - 10:37 PM

EFI is its own separate thing from Grub (well sorta)

And yes you can accidentally overwrite the efi partition on windows on some distros.

I have done it by mistake on Ubuntu myself (this why i personally use a separate efi partition)

 

It should be noted that grub only partially supports UEFI, as it was made before EFI and UEFI was made standard on newer machines.


Edited by MadmanRB, 26 June 2018 - 10:41 PM.

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#9 pcpunk

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Posted 26 June 2018 - 10:49 PM

That makes sense MadmanRB.

 

I'm now looking at the entry at UEFI Community.  Fourth down under "General principles" Sentence #2 that I highlighted.  Seeds as though everyone uses different terminology, and is making me crazy.  I know I can just follow at least that one tutorial that Nick posted but I'm in no hurry and trying to understand this a little better before I go and muck things up.

 

6. Then:
  • nothing special is required if you use the automatic installer of Ubuntu ("Install Ubuntu alongside others" or "Erase the disk and install Ubuntu"). Important: if you have a pre-installed Windows and you want to keep it, do not choose "Erase the disk and install Ubuntu".
  • if you use the manual partitioning ("Something else"), the difference is that you will have to set the /boot/efi mount point to the UEFI partition.

Thanks Madman, getting tired of working on pc's for the day.


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#10 pcpunk

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Posted 01 July 2018 - 11:39 AM

Can anyone clarify that last sentence in bold above?  I assume there are more ways than one to do this so am just curious what this means exactly.

 

Is it accepted that a Windows 10 Feature Update will overwrite the bootloader, or does this only happen sometimes.  Or, is this why we should take the approach of the directions NickAu posted, and that are on the Official Mint Install page?

 

I wonder what consequences are when Installing Boot Loader to the EFI Partition? 

 

Thanks, pc


Edited by pcpunk, 01 July 2018 - 02:30 PM.

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