SYNC(1M) UNIX Programmer's Manual SYNC(1M)
sync - update the super block
sync
_S_y_n_c executes the _s_y_n_c system primitive. If the system is
to be stopped, _s_y_n_c must be called to insure file system
integrity. See _s_y_n_c(2) for details.
sync(2), update(8)