Also be more careful about markup: use & not just &.
character in the command. The simplest useful command is something
like
<programlisting>
-archive_command = 'test ! -f /mnt/server/archivedir/%f && cp %p /mnt/server/archivedir/%f' # Unix
+archive_command = 'test ! -f /mnt/server/archivedir/%f && cp %p /mnt/server/archivedir/%f' # Unix
archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"' # Windows
</programlisting>
which will copy archivable WAL segments to the directory