Mac OS X Mountain Lion, Permission change makes unable to boot.


Hi everyone,
I change Everyone No Access on my HD. The system cannot startup now.
After that I try to logout but could not. So I press the power button and shut it down. Then I restart but It can never pass Apple Logo. No spinning gear shows up.

Anyone, please help me know what went wrong and how to fix it.
Actually I am tech savvy but in fear of worsen the problem, I did not do other thing yet.

my machine is MacBook Pro late 2011. core i5, 2.4 GHz, RAM 4GB, running Mountain Lion.

Thanks in advance.
for "tech savvy", you screwed up now :D
When you changed the HD permissions to "Everyone no access", you got exactly what you asked for - no access, for everyone (which includes you)

This should fix your problem: (compliments to g/re/p for this)

1) Boot into single user mode, type mount -uw / and press return

2) type chmod 775 /Volumes/'Macintosh HD' and press return

3) type reboot and press return

Change the volume name to whatever yours actually is, if not 'Macintosh HD'