How to backup VMWare ESXi using free tools?

Solution 1:

Here is an article that describes the configuration and has scripts that you can use to perform a back of ESXi 3.5 and 4.0. I haven't deployed this myself but it is on my todo list to possibly setup.

At the moment I am just running backups within the guests.

Solution 2:

Zoredache has already showed the right way to go. ghettoVCB.sh is your tool of choice. It works quite well, but make sure you also read the articles by Raj Perumal (Part 1, 2 & 3).