netPBM tutorials wanted

I need to make thumbnail images from whatever images (probably jpeg) that reside in a certain directory. My host only has netPBM installed, (no imagemagik, no GDlib) and I'm having trouble turning up any good instructions or tutorials for netPBM. I have a little programming knowledge but shell, bash, ect. and Linux in general are foreign to me so please no RTFM replies. I have... and it didn't tell me anything.

Thanks for your help

~Butcher~