How to create a bootable ESXi USB disk on macOS

Insert USB drive in your computer. Open Terminal and list the mounted disks using the following command (note disk#):

$ diskutil list

Now we will format the disk using FAT32 filesystem and MBR partition map

$ diskutil eraseDisk MS-DOS "ESXI" MBR disk#

Unmount the USB drive:

$ diskutil unmountDisk /dev/disk#

Next we need to flag the first partition as bootable:

$ sudo fdisk -e /dev/disk#
f 1
w
q

Mount the ESXi ISO image and copy all the files to the USB drive.

Locate the file ISOLINUX.CFG on the USB drive and rename it to SYSLINUX.CFG

mv /Volumes/ESXI/ISOLINUX.CFG /Volumes/ESXI/SYSLINUX.CFG

Open the SYSLINUX.CFG file and append the bold characters to the existing line:

APPEND -c boot.cfg -p 1

Save and close the file, and eject the USB drive. Now you can boot from the USB drive.