1.\"
2.\" Copyright (c) 1995
3.\"	Mark Murray.  All rights reserved.
4.\"
5.\" Redistribution and use in source and binary forms, with or without
6.\" modification, are permitted provided that the following conditions
7.\" are met:
8.\" 1. Redistributions of source code must retain the above copyright
9.\"    notice, this list of conditions and the following disclaimer.
10.\" 2. Redistributions in binary form must reproduce the above copyright
11.\"    notice, this list of conditions and the following disclaimer in the
12.\"    documentation and/or other materials provided with the distribution.
13.\"
14.\" THIS SOFTWARE IS PROVIDED BY MARK MURRAY AND CONTRIBUTORS ``AS IS'' AND
15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24.\" SUCH DAMAGE.
25.\"
26.\" $FreeBSD: src/usr.sbin/rndcontrol/rndcontrol.8,v 1.13.2.2 2001/12/21 09:05:32 ru Exp $
27.\" $DragonFly: src/usr.sbin/rndcontrol/rndcontrol.8,v 1.7 2007/06/13 14:27:41 swildner Exp $
28.\"
29.Dd October 20, 1995
30.Dt RNDCONTROL 8
31.Os
32.Sh NAME
33.Nm rndcontrol
34.Nd a utility for manipulating the
35.Pa /dev/random
36device
37.Sh SYNOPSIS
38.Nm
39.Op Fl q
40.Op Fl s Ar irq_no
41.Op Fl c Ar irq_no
42.Sh DESCRIPTION
43The
44.Nm
45command is used to set which interrupts are used to help add entropy
46to the CSPRNG maintained by the kernel.
47The
48.Pa /dev/random
49and
50.Pa /dev/urandom
51devices are the user interface to this source of randomness.
52Any changes take effect immediately.
53.Pp
54The following command line options are supported:
55.Bl -tag -width indent
56.It Fl q
57Turn off all output except errors.
58.It Fl s Ar n
59Allow IRQ
60.Ar n
61to be used as a source of randomness.
62This option may be repeated for
63more than one IRQ.
64.It Fl c Ar n
65Stop IRQ
66.Ar n
67from being used as a source of randomness.
68This option may be repeated for
69more than one IRQ.
70.El
71.Pp
72By default, all IRQs will help develop entropy.  The kernel uses a
73rate-limited helper thread to add the actual entropy and even fast
74interrupts should not detrimentally affect a running system.
75.Sh FILES
76.Bl -tag -width ".Pa /dev/urandom" -compact
77.It Pa /dev/random
78secure random device
79.It Pa /dev/urandom
80random device
81.El
82.Sh SEE ALSO
83.Xr srandomdev 3 ,
84.Xr random 4
85.Sh HISTORY
86The
87.Nm
88utility first appeared in
89.Fx 2.1.5 .
90.Sh AUTHORS
91.An -nosplit
92.An Theodore Ts'o
93wrote the core code.
94.An Mark Murray
95ported this code to
96.Fx
97and wrote the support routines and constructed the man pages.
98.Sh BUGS
99Sure to be some.
100