Yellow dog linux on the ps3?

ok i have installed it on my ps3 befor but then i formated the hdd and now i tryd to install it agin in the past but i thout my dvd was no good anymore so i hade to contact sony i think to be abel to exit the install prosses and i remmember something bout boot-os-ps3 or boot-ps3-os i just cant remmeber where and how to get to the spot where i typ it in and what way i typ it in how do i exit the install proses and boot my ps3 os