Create a Bootable UEFI Windows USB stick from an ISO on Apple macOS

create-win10-usb-on-mac.sh

# Just a quick update for GPT and to use `rsync` instead of `cp`!
# That means this applies to UEFI boot, though for legacy BIOD boot, feel free to swap
# GPT to MBR below.

# Requires https://homebrew.sh to split the install.wim file
brew install wimlib

# First, we need to find our device. BEFORE inserting your USB drive, run the
# following:
diskutil list

# This will output a bunch of info about all of the disk drives connected to
# your Mac. Each entry will have a header in the form "/dev/diskX", where X is
# some number starting at 0. Now, insert your USB drive and run the command
# again. You should see a new entry. Make note of the name (ie, /dev/diskX).

echo "TIME TO PLUG IN YOUR USB STICK! YOU HAVE 30 SECONDS!"
sleep 30 

diskutil list

# Now we need to format the drive for MS-DOS and include a Master Boot Record.
# In the command below, replace "diskX" with the identifier of your USB drive.
# WARNING: this will delete everything on the USB! If you've got nothing else inserted
# it's probably disk2... but you've been warned!
diskutil eraseDisk MS-DOS WIN10 GPT diskX

# In the command above, MS-DOS is the format of the partition that will be
# created on the USB. WIN10 is the name of that partition (it'll appear in
# Finder as the name of your USB). MBR tells diskutil to create a Master Boot
# Record, which is necessary for the USB to be bootable.
#
# Now, "open" the Windows ISO (assumes you've only got one downloaded :P ):
open ~/Downloads/Win10*.iso

# Your Mac will "mount" the ISO as if it was a drive. A Finder window will open
# to show the contents of the ISO. Close the Finder window; you don't need it.

# You should see a new entry. This time, we're looking for what's in the NAME
# column. You should see something funny like CCCOMA_X64FRE_EN-US_DV9 (free download from Micrososft.com. 
# The name may differ depending on which ISO you downloaded.  

# And copy all the files other than `install.wim` over to our USB drive:
sudo rsync -avh \
 --progress \
 --exclude=sources/install.wim /Volumes/CCCOMA_X64FRE_EN-US_DV9/ /Volumes/WIN10

# This will take a while; there's a lot of data. Grab a drink; relax.

# Split the WIM to an SWM file in the destination
wimlib-imagex split /Volumes/CCCOMA_X64FRE_EN-US_DV9/sources/install.wim /Volumes/WIN10/sources/install.swm 3800

# Once it's done, you can eject both the USB and the ISO. First, cd to another
# directory otherwise OSX will not allow you to unmount the ISO (since being in
# the directory means the ISO is "in use"):
cd ~

# Eject the USB using the diskX (probably disk4 at this point):
diskutil list | grep CCC
diskutil eject /dev/disk4

# Eject the ISO using the diskX identifier from the fifth step above:
diskutil eject WIN10 --force

# Now insert the USB into your computer, (re)boot, and select the USB from the
# boot device menu (you may need to press some key to show the boot device menu
# - on my machine it's F12).