Dualboot Win10/Manjaro with GRUB in UEFI – #8 by fahrer17 – Installation & Boot

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.
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.
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.
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.
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.