A couple of days ago while I was free at the office I thought that it would be more secure to put a permissions rule to the whole of my Hard Drive, of my PowerPC Quad. so I made the permissions so I changed the permissions into "Read only" to the Ownership and "No Access" to the "Access" and "Others" menus, that all in the info windows of the HD, I clicked on "Apply to enclosed Items" and waited and waited.... for around 10 mins I stated to get worried that I have done something wrong so I "Forced Quit" the finder and continued using the system normally.
the problem was discovered when I needed to restart the machine so I restarted it, but the system failed to start OSX, instead I was infront of a black screen and white text that reminded me of the late DOS, saying something like: Welcome to Darwin Console please log in and I logged in with my usual username and password and the where accepted but stayed in this Darwin thing!...
I had to search on the net for a similar matter and found some on several forums but without any satisfying answer.
For those who are X-DOS users must remember the command "Win" that starts Windows 3.11 or Windows 95 from DOS, and I was sure that there must be a similar command that would take me directly to my OSX and tried all the words the came to my mind "sys, osx, mac..." and I discovered the command "exit" which means "log out"... whatever that is not the issue. I called everyone I know who I could tell me that GOLDEN COMMAND, but non could give any...
I remembered then that I did something related to permissions,
so I decided to startup the machine form my system DVD and run Disk Utility to repair permissions, then restart....
WOW I got my OSX back guys
the lesson I learned here is: permissions shouldn't ever be changed to the root HD because apparently it affects the ability of the system to access the startup files