Starting from a clean 3.55 OFW..

AFTER BACKING UP YOUR INTERNAL HARD DRIVE AND QUICK FORMAT ON PS3

Part 1

1. Install Gitbrew's CFW www.tinyurl.com/355-git (DO NOT USE "Gitbrew SPECIAL")
2. When installation is finished, go to recovery menu and choose "Restore PS3 System"
3. Now your GameOS will display less of your HDD space (your new *nix partition = missing space)
4. Run setup_flash_for_otheros.pkg (for all PS3 models)
5. Reboot
6. Store this file - "dtbImage.ps3.bin" - on USB drive, plug it in and run install_otheros.pkg - ** tinyurl.com/phat-ps3 or tinyurl.com/slim-ps3-pb ** - : NOTE, for phat's rename "dtbImage.ps3.bin.minimal" => "dtbImage.ps3.bin"
(Furthest right USB port works best, try different USB ports if you don't get any beeps)
7. Run boot_otheros.pkg
8. Run reboot.pkg
9. You should be in petitboot now.

Part 2

Select "exit to shell" from Petitboot

   1. cd /
   2. wget tinyurl.com/create-hdd1
   3. chmod 755 create_hdd_region.sh
   4. ./create_hdd_region.sh auto

REBOOT PS3 AFTER STEP 4 COMPLETES

   5. parted /dev/ps3dd
   6. mklabel gpt
   7. mkpart primary 0 2GB
   8. print
   9. mkpart primary 2GB (the rest of the hard drive here.) 
  10. quit.

*At this point, you can go for the simple alternative and insert Red Ribbon(RC5 is latest as of writing this) on DVD or extract the .iso to USB and insert, then select the first option from Petitboot main menu to boot Red Ribbon and install from the desktop.* : NOTE - Don't use the AsbestOS option for Red Ribbon.