Only superuser can run this. Fails if password is incorrect. Does sanity checking on the data. Any user can run this. Intended for use by CGI scripts where users update their own passwd entry.
Mirrors change if the loginid exists in the mirrored domain.
There is no way to manipulate just the passwd.byname or just the passwd.byuid map. Normally, this isn't a problem, but if you ever change the uid of an existing entry, you must proceed with caution. Be sure to run mirrorpw if the entry is mirrored. It is possible for two passwd.byname entries to have the same uid, but there can be only one passwd.byuid map entry. Don't forget to run mirrorpw if any entries should be mirrored.