FreeBSD/cddl/contrib/opensolaris/cmd/zpool/zpool_main.c
/*
 * zpool attach [-f] <pool> <device> <new_device>
 *
 *	-f	Force attach, even if <new_device> appears to be in use.
 *
 * Attach <new_device> to the mirror containing <device>.  If <device> is not
 * part of a mirror, then <device> will be transformed into a mirror of
 * <device> and <new_device>.  In either case, <new_device> will begin life
 * with a DTL of [0, now], and will immediately begin to resilver itself.
 */
zpool attach [-f]   
-f      Force attach, even if  appears to be in use.

Attach  to the mirror containing .  If  is not
part of a mirror, then  will be transformed into a mirror of
 and .  In either case,  will begin life
with a DTL of [0, now], and will immediately begin to resilver itself.
zpool attach [ - f ] - f Force attach even if appears to be in use . Attach to the mirror containing . If is not part of a mirror then will be transformed into a mirror of and . In either case will begin life with a DTL of [ 0 now ] and will immediately begin to resilver itself .
int
zpool_do_attach(int argc, char **argv)
{
	return (zpool_do_attach_or_replace(argc, argv, B_FALSE));
}
int zpool_do_attach ( int argc , char * * argv ) { return ( zpool_do_attach_or_replace ( argc , argv , B_FALSE ) ) ; }
zpool attach [-f] <pool> <device> <new_device>
      -f      Force attach, even if <new_device> appears to be in use.
zpool attach [ - f ] <pool > <device > <new_device > - f Force attach even if <new_device > appears to be in use .