I know there is an official document about this and lots of information on the web, but I wanted to share my version...I think its mighty useful. This is from a Windows workstation and the procedure is written from memory, but it should get you there. This should also help those wanting to PXEboot. Also, if you get a big enough drive, you can save the OVA files for vCenter etc and have the whole kit-and-kaboodle in one place!
-----<I'm not responsible if you blow up your workstation e.g. format your hard drive>-------
1.Download SYSLINUX from http://www.syslinux.org/wiki/index.php/Download and unzip the contents. For the example, I'll assume you unzipped to c:\temp\syslinux 2.Insert a USB flash drive (even the new ones that don't have the RMB set work with this) 3.Identify what drive letter the flash drive received. For the example, I'll assume E: 4.Make sure it is formatted FAT32 5.Launch an elevated command prompt (as administrator) 6.type C:\temp\syslinux\bios\win32\syslinux.exe -mfa E: (MAKE SURE E IS YOUR FLASH DRIVE) and hit enter 7.Copy the following files to the root of your flash drive •C:\temp\syslinux\bios\memdisk\memdisk •C:\temp\syslinux\bios\com32\menu\menu.c32 •C:\temp\syslinux\bios\com32\elflink\ldlinux\ldlinux.c32 •C:\temp\syslinux\bios\com32\libutil\libutil.c32 8.Copy the ISO files of the ESXi installs you need (yep, you can have more than one depending on the size of the drive) 9.Create a syslinux.cfg file with the following (modify as you need for more entries)
DEFAULT menu.c32 MENU TITLE ESXi-5.5.0-1331820 Installation Menu NOHALT 1 PROMPT 0 TIMEOUT 80 LABEL Universal Image KERNEL memdisk APPEND iso INITRD /ESXi-5.5.0-1331820-Universal.iso MENU LABEL ESXi-5.5.0-1331820 ^Universal Image
Please consider marking this answer "correct" or "helpful" if you found it useful.
VMware, SAN/NAS, Networking and Server Infrastructure Engineer