On a recent project, I had to install ESXi onto an HP DL380 G6. This chassis is decidedly non-optical drive friendly, as previous chassis would allow you to just snap a DVD drive into it. The G6 now requires you to disassemble a fair portion of it to install a drive. I had 140 servers to do, so installing DVD drives wasn’t an option (plus it saved me $14,000 in my budget). So, after fiddling around a bit, this is what I came up with.
All you need for an ESXi install is:
A thumb drive of at least 512 megabytes
A copy of UNetbootin
The ISO for ESXi
Download UNetbootin for Windows. I had used v3.77 originally, and it looks like it is up to v4.71 now.
Plug in the drive, make sure the server is set to boot from USB, and away you go!