C3rd

Restart your computer and press COMMAND + S then this will enter to terminal mode. First you need to mount the "root" path before you can modify the disk.

:/ root# mount -uw /

Now after mounting the root path, you have two option here, factory reset or reset password of a user so you can access the files. Factory Reset In factory reset, all you need is to delete the file /var/db/.applesetupdone then OS X will detect that the system has run the first time (but the data are all intact).

rm /var/db/.applesetupdone

User Reset Password In user reset password, this is what you will do:

1. go to /Users directory then list the files and folders
2. whoever you want to reset the password, just type passwd <username>
3. then this will ask you for the new password and confirm new password
4. that's it

:/ root# cd /Users
:/ root# ls -lsa
:/ root# password user1
Enter New Password: 
Confirm Password:

:/ root# reboot

then type exit or reboot or restart the machine. then you all good to go...