If you have a host that doesn’t have a CD-ROM or want to modify oem.tgz, you may find it easier to extract the ISO image to a USB flash drive and then run your install from it. The below method will allow you to create a USB flash drive which you can then use to install ESXi to a local drive on your host. If you wish to boot from a USB flash drive, click here
1) Download and extract the latest version of Syslinux. For this process, I used version 3.72.
2) Insert the USB flash drive that you plan to use. It will require about 300 MB free space for the ESXi install files and should be formatted as FAT32. If you’re using Windows make a note of the drive letter that is assigned to the drive. With Linux you can run fdisk -l to determine the device node (/dev/sdX).
3) For Windows run the command ..\win32\syslinux.exe <drive letter> and for Linux run ../linux/syslinux /dev/sdX. This command will alter the boot partition on the device and copy over the file ldlinux.sys to the root directory.
4) Extract the contents of the ESXi install CD to the USB flash drive. If you plan to modify oem.tgz you can copy over the file at this time as well.
5) On the USB flash drive rename the file isolinux.cfg to SYSlinux.cfg.
The USB flash drive will now be ready to be used in a host to install ESXi. If you have problems booting the flash drive, you might want to try one of these options of the syslinux command in step 3
-s - this option causes Syslinux to use simpler code which boots easier on some older BIOSes. -f - this option will force the install -m - (Windows only) - this will install a bootable MBR sector at the beginning of the drive -a - this marks the partions as active (bootable)