A process cannot change the owner of a file, unless it is running with UID 0.
A process cannot change the group ownership of a file to a group in which it is not currently a member, unless it is running as UID 0.
For more information, see chown(2).
1, indicating that POSIX semantics are used
0 = POSIX semantics not in force or 1 = POSIX semantics used
When POSIX semantics are not wanted. Note that turning off POSIX semantics opens the potential for various security holes. Doing so also opens the possibility of a user changing ownership of a file to another user and being unable to retrieve the file without intervention from the user or the system administrator.