\fBshadowconfig\fR on will turn shadow passwords on; \fIshadowconfig off\fR will turn shadow passwords off\&. \fBshadowconfig\fR will print an error message and exit with a nonzero code if it finds anything awry\&. If that happens, you should correct the error and run it again\&. Turning shadow passwords on when they are already on, or off when they are already off, is harmless\&.
.PP
Read \fI/usr/share/doc/passwd/README\&.debian\fR for a brief introduction to shadow passwords and related features\&.