Create a new admin account in single user mode.
This is useful if for some reason a user has become corrupted or simply wont complete the login sequence for any reason. It is non-destructive to existing data. So it is safe to use as a means for gaining access with admin rights to perform further actions on the OS.
power on your machine and press command S as soon as you hear the chime.
(assumes no firmware password set)
at the shell prompt type the following :
this runs fsck kinda like disk utility repair feature to check your file
system for corruption.
when fsck is finished type:
“/sbin/mount -uw /”
this sets your hard drive to allow changes.
now type these commands in succession pressing return after each line.
this will run the mac os x account setup assistant at boot and create a
new mac os x user account for you with admin rights.
you can use this account to find out the user name for your other account
and reset its password.