When creating or modifying users and groups, these conditions
will cause an error:
a colon (:) or newline character in any attribute
(including user name, home directory, comment)
a misspelled or nonexistent login shell (or path name)
an illegal user or group name (names cannot begin with a number
or exceed 8 characters in length)
an illegal UID or GID number (they must
fall within the minimum and maximum values
listed in the User or Group selections
of the Options menu in the Account Manager)