This guide will help you change the screen resolution in ubuntu Linux on the ps3

Changing Screen Size
You will need a HD TV or monitor to change the resolution

1. Open Terminal (Applications> System> Accessories> Terminal)
2. Type “sudo apt-get install ps3pf-utils”, this will install the ps3videomode command
3. Now type ‘ps3videomode -v’, this will provide all options for the command
4. Now you want to discover which video modes work, just start guessing. Personally I use ‘ps3videomode -v 37′ for 1080p, if you try an option and it garbles your text press the up arrow delete the number and type 1 and press enter. This should bring it back to the way it was if not press enter, and type ps3videomode -v 1.
5. Keep trying your options, if an option garbles your text it probably works but you just need to change it in the kboot.conf file before Linux boots. If it displays just a black screen it’s probably a bad mode, try another.
6. Now to assign your video mode at startup type ’sudo su’, you should now be root be careful in this mode as you can screw some stuff up and have to reinstall.
7. Type ‘nano /etc/kboot.conf ‘. This opens the kboot in a text editor. Add ‘ps3fb:mode:xx’ at the end of each quote, it should look like the following.
   Linux='/boot/vmlinux blah blah blah quiet splash video=ps3fb:mode:xx'
Old='/boot/vmlinux blah blah blah quiet splash video=ps3fb:mode:xx'
   Remember to change the xx to whatever video mode you decided upon.
8. Now Press Control-X, y, save as kboot.conf by pressing enter
9. Now type ’sudo reboot’

0:auto mode
  YUV 60Hz  1:480i  2:480p  3:720p  4:1080i  5:1080p
  YUV 50Hz  6:576i  7:576p  8:720p  9:1080i 10:1080p
  RGB 60Hz 33:480i 34:480p 35:720p 36:1080i 37:1080p
  RGB 50Hz 38:576i 39:576p 40:720p 41:1080i 42:1080p
  VESA     11:WXGA 12:SXGA 13:WUXGA

  full screen mode: <video mode ID> + 128
  dither ON mode  : <video mode ID> + 2048