I managed to corrupt my NetInfo database on an OS 10.4 server a few weeks ago by not cleanly unmounting the drive after booting from DVD and resetting the admin password. Long story short, this left me with no users on the system at all. With no users, I could not log in to create one, so I had to blow away the NetInfo database and restore it to factory defaults. This should only be done when you only have a small number of users, and don’t mind having to re-create them. Only the user account information is deleted, and the user directory is retained, but you will have to manually add any users you may have back into the system through the GUI, making sure that the new “user” references the old “user’s” account directory.
If you have more than just one or two users, you should use the procedure to recover from one of your NetInfo database backups. A backup of your this database is made at 3:15 every day so long as the computer is running. It is stored in “/var/backups/”, and here are some instructions on how to recover it from it. If, however, you don’t care about re-adding users, and simply want to get into your system quickly, or if you don’t have a backup to restore from, here is how you can do it:
BEWARE: THIS WILL COMPLETELY ERASE ALL USER ACCOUNT INFORMATION FROM THE SYSTEM!!! You are warned.
1) Start by booting your Mac into single user mode. To do this, hold down both the “Apple” and the “s” keys as the system boots.
2) The system will have mounted the “/” filesystem read-only to protect against data loss. To get “/” mounted read-write, we have to run two commands:
# /sbin/fsck -fy
# /sbin/mount -uw /
3) Now “/” is mounted read-write, so we can start with the real work. First, rename your existing NetInfo database to something else so the OS will not see it on the way up:
# mv /var/db/netinfo/local.nidb /var/db/netinfo/local.nidb.bad
# mv /var/db/netinfo/network.nidb /var/db/netinfo/network.nidb.bad
4) Next, remove the “.AppleSetupDone” file so the OS will kick you back into the installer upon boot and you can recreate your users.
# rm /var/db/.AppleSetupDone
5) Finally, reboot your system and recreate your users, making sure they are pointed towards their existing account directories.