>> Assuming we do steps 1 and 2 above, do we get into any problems with >> POSIX compliance if the default basic privilege set does not include >> PRIV_SYS_SYNC?
There is no such thing as a "default basic set". There's a "basic set" and there's the "default set" users get when they login; they are generally the same but need not be. An administrator CANNOT manipulate the basic set; he can manipulate the default. Making sync() privileged would violate POSIX; but with basic privileges that is not an issue because everyone gets them in the default configuration. Casper