Dualboot Win10/Manjaro with GRUB in UEFI

Hi there.

I recently built a new PC which is running Win10. Now I want to add a 2nd SSD on which I would like to install Manjaro (been using it for about 6 years now).
Since my old PC was still using BIOS instead of UEFI I am a bit unconfident on how to install Manjaro including the GRUB menu to choose from when booting. I read a lot but the more I read the less I seem to know… :confused:

I found this great video on YT where it is perfectly explained imo:

In short:

  • Download and boot into Manjaro
  • Install it with manual partitioning (not sure wether I will install a separate /home partition though)
  • Edit Win10 boot partition as seen at 5:23

Now is this the way to go? If so it seems quite simple and I don’t know why I am so nervous about this…


(I hope this wasn’t asked before to often… :flushed:)

You should create

  1. /boot/efi FAT32 300MB
  2. swap partition ~ RAM size
  3. / (root) 100GB
  4. /home rest of SSD
  1. First and foremost, download your favorite flavor of Manjaro, verify that the checksums match those on the site, and then “burn” them to a CD/DVD or USB stick.

  2. Next, shut down Windows completely ─ “fast boot” must be disabled, because it’ll leave your Windows filesystems in a half-open state, with as a result that they will be read-only in GNU/Linux.

  3. Enter your UEFI firmware configuration utility ─ this is usually accomplished by pressing F11 or some other key during boot-up. Which key you need to press will usually flash on the screen for a few seconds.

  4. In your UEFI settings, you must disable CSM, also known as “legacy mode”, “legacy BIOS mode”, “BIOS emulation”, or something like that. Also make sure that Secure Boot is switched off. Save your settings and continue booting.

  5. Boot up from the CD/DVD/USB and begin the installation.

Your drive will contain a partition designated as “EFI system partition”, or something of the likes. This partition will be approximately 260 to 300 MiB in size. The installer might complain that this is too small, but you can ignore that warning.

Create your partitions ─ whether manually or automatic. Then, choose your mountpoints. The EFI system partition must always be mounted at /boot/efi. Your root partition must be mounted at /. If you create a separate /home partition, make sure you set the mountpoint for that too.

If you create a swap partition, then that has no mountpoint. Depending on the amount of RAM you have in your machine, you may not need a swap partition, unless you plan on hibernating the machine ─ i.e. suspend-to-disk. In that case, your swap partition should be about 1.5 to 2 times the size of your RAM.

The GRUB boot loader will automatically be installed in the EFI system partition. When the machine boots, you’ll have the option of choosing an operating system straight from within the UEFI firmware boot menu, and every time you choose Manjaro, you will see another boot menu ─ this is the GRUB menu ─ which will also contain an entry for booting Microsoft Windows.

One last piece of advice… Microsoft Windows prefers the hardware clock to be in local time, while GNU/Linux prefers the hardware clock to be in UTC.

It is possible to force Windows into using UTC as well, but this requires changing a registry parameter, and I cannot tell you how to do that ─ I don’t use Windows. On the other hand, it is perhaps easier to tell GNU/Linux to use local time as well.

The reason why this is important is that if both your operating systems are set to a different hardware clock time, then there will be a discrepancy in the shown time. So they both need to have the same setting for the hardware clock.


Thank you very much for this very detailled reply! I will dive into this much more as soon as I have a few free hours. I miss Manjaro… :wink:
After a quick read I think it ist basicly the approach described in the video

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Could you tell me please why I need a separate /boot/efi partition and not using the one that is already there?
I don’t want to replace Win10, I’d like to have a dual boot machine.

Strictly speaking, it’s not necessary. The whole idea of an EFI system partition is that it’s shared among all installed operating systems.

However ─ and here’s the catch ─ it is not uncommon for a Microsoft Windows update to screw up the contents of the EFI system partition, and as such, prevent you from booting anything other than Windows.

Such is the price you pay for using The Devil’s Operating System™ ─ and I’m not talking about Manjaro here. :stuck_out_tongue:


@fahrer17 Ermanno from EF linux has a second video called ‘Update on Dual Boot’ on youtube where he describes the second method with a separate boot/efi partition. Check it out.

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@raguse Thank you for the info! I wanted to check out his channel anyway, he seemed rather convincing in his video :slight_smile:

So I just tried to install Manjaro to my 2nd SSD.

So I created, mounted and flagged the partitions as shown by Ermanno respectively as I understood Aragorn’s post (it’s not the first time I install a Linux :slight_smile: ):

When hitting NEXT I get this error message (which Ermanno didn’t get):
It basicly says that Manjaro needs a EFI system partition otherwise it won’t start.

What did I miss or am I doing wrong or can I simply ignore this message?

Since I was too confused I stopped the installation.

You chose to install the /boot/efi onto the same partition as the existing Windows bootloader (the 100 MiB FAT32), is it? It looks like.
Have you thought of placing the /boot/efi partition onto a separate 200-300 MiB partition?
Make sure to set the right flags.

No, I didn’t try to install anything in /boot/efi, instead I changed the existing Win10 efi partition to mount in /boot/efi including flag “boot” as it was shown in Ermanno’s video. Actually I only created a /home and a / partition.
I don’t have a problem creating more partitions as long as I can be sure not to mess up my existing Win10 installation (my kids would kill me if they don’t have access to their Steam games anymore :slight_smile: . I know I can fix this but I won’t have the time before X-mas).
In Ermanno’s video everything seemed quite simple so I’d like to prefer this method. If it isn’t possible anymore I’ll have to go the other way of course :man_shrugging:

both ways have pros and cons. You will have to make a choice.
Not sure if 100 MiB is enough for Manjaro. In my last installation it asked me to provide at least a 300 MiB boot partition. I created a separate one instead of extending the existing Windows boot and installation was smooth without any issues. You might have to extend the boot partition first. Again, set the flags correctly.

Make sure that you understand what you are doing. Generally speaking you can can always correct the bootloader afterwards if anything goes wrong. I think Ermanno also shows how to correct things.

Edit: I read the error message again and it says that you require at least 300 MiB as boot. You only have 100 MiB currently. If you extend the boot partition, do NOT select ‘format’ partition!!

OMG, now I know what you mean with Ermanno’s Update video :man_facepalming:
I always thought it is about updating the bios/efi partition. Instead it is an update of his previous video.
Whatever, it was very interesting!
When creating the new Manjaro efi partition: Where do I place it? On my first (=Win) SSD or on my 2nd (=Manjaro) SSD?

yeah, Ermanno explains 2 different boot partition setups with dualboot in these videos.
where to place it? I guess it wouldn’t matter much. To keep disk 1 clean you might opt for disk 2.
You can always wipe disk 2 and start over again, just in case.
don’t consider this a recommendation. you will have to make your own choices based on your desired outcome. good luck!

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Best would be on the drive where you install Manjaro.


@raguse + @Aragorn
Sounds like I could do a clean installation on the 2nd SSD without touching my existing system - great!

When installing everything on SSD #2, do I have to change the boot order in EFI?

Sorry if these questions sound stupid but I have absolutely no knowledge about EFI systems.

Not necessarily, unless you want that.

I agree with Aragorn. If I am not mistaken Grub should place Manajro at first place in boot menu. Am I correct @Aragorn ?

That’s what I think, but I can’t be sure. I don’t use anything other than Manjaro. :wink:

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