How to restart PS3 OS when 'OtherOS' is default

if kboot does not work

In general these are two useful tips:
1) Pressing and hold down the power button for few seconds until it switches off the PS3.
2) Pressing and holding the power button for few seconds when the PS3 is already off will boot the game OS.

If you are already running your non Game OS, you can try
Type at kboot prompt:

ps3-boot-game-os

Also works at a console prompt within *nix.

YMMV

I assume the steps are the same if you're trying to play a (Blu-Ray)? DVD...

Thanks!

To play a DVD, you must boot to the PS3 OS, then choose Play DVD from the menu. (or something like that)