Use the following steps if two user accounts have duplicate user names or UID numbers:
If two user accounts have duplicate UID numbers, use the Users tool to remove one account and add it again with a different UID number. You cannot use the Users tool to modify a UID number of an existing user account.
If two user accounts have duplicate user names, use the Users tool to modify one of the accounts and change the user name.
One part of a user account that you can change is a user's group memberships. Select the Properties option from Users tool's Action menu to add or delete a user's secondary groups. Alternatively, you can use the Groups tool to directly modify a group's member list.
You can also modify the following parts of a user account:
Passwords and password options
Home directory and home directory access
Rights and roles
Occasionally, you might need to temporarily or permanently disable a user account. Disabling or locking a user account means that an invalid password, *LK*, is assigned to the user account, preventing future logins.
The easiest way to disable a user account is to lock the password for an account with Users tool.
Other ways to disable a user account: set up password aging or change the user's password.
When you delete a user account with the Users tool, the software deletes the entries in the passwd and group files. In addition, the files in the user's home directory and mail directory are deleted also.