NetBSD/sbin/rndctl/rndctl.8

.\"	$NetBSD: rndctl.8,v 1.26 2020/05/07 19:09:26 riastradh Exp $
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.\" Copyright (c) 1997 Michael Graff
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.Dd August 10, 2014
.Dt RNDCTL 8
.Os
.Sh NAME
.Nm rndctl
.Nd kernel entropy pool management tool
.Sh SYNOPSIS
.Nm
.Op Fl CcEe
.Op Fl d Ar devname | Fl t Ar devtype
.Nm
.Op Fl lsv
.Op Fl d Ar devname | Fl t Ar devtype
.Nm
.Op Fl i
.Fl L Ar save-file
.Nm
.Fl S Ar save-file
.Sh DESCRIPTION
The
.Nm
program displays statistics on the current state of the
.Xr rnd 4
device, and controls which sources are allowed to contribute to the
entropy pool maintained by
.Xr rnd 4 .
.Pp
The following options are available:
.Bl -tag -width 123456
.It Fl C
Disable collection of timing information for the given
device name or device type.
.It Fl c
Enable collection of timing information for the given
device name or device type.
.It Fl d
Only the device named
.Ar devname
is altered or displayed.
This is mutually exclusive with
.Fl t .
.It Fl E
Disable entropy estimation from the collected timing information for
the given device name or device type.
If collection is still enabled, timing information is still
collected and mixed into the internal entropy pool,
but no entropy is assumed to be present.
.It Fl e
Enable entropy estimation using the collected timing information
for the given device name or device type.
.It Fl i
With the
.Fl L
option to load a seed from a file, ignore any estimate in the file of
the entropy of the seed.
This still loads the data into the kernel, but won't unblock
.Pa /dev/random
even if the file claims to have adequate entropy.
This is useful if the file is on a medium, such as an NFS share, that
the operator does not know to be secret.
.It Fl L
Load saved entropy from file
.Ar save-file
and overwrite it with a seed derived by hashing it together with output
from
.Pa /dev/urandom
so that the new seed has at least as much entropy as either the old
seed had or the system already has.
If interrupted, either the old seed or the new seed will be in place.
.It Fl l
List all sources, or, if the
.Fl t
or
.Fl d
flags are specified, only those specified by the
.Ar devtype
or
.Ar devname
specified.
.It Fl S
Save entropy pool to file
.Ar save-file .
The file format is specific to
.Nm
and includes an estimate of the amount of saved entropy and a checksum.
.It Fl s
Display statistics on the current state of the entropy pool.
.It Fl t
All devices of type
.Ar devtype
are altered or displayed.
This is mutually exclusive with
.Fl d .
.Pp
The available types are:
.Bl -tag -width "diskx"
.It Ic disk
Physical hard drives.
.It Ic net
Network interfaces.
.It Ic tape
Tape devices.
.It Ic tty
Terminal, mouse, or other user input devices.
.It Ic rng
Hardware random number generators.
.El
.It Fl v
Verbose output.
.El
.Sh SEE ALSO
.Xr rnd 4 ,
.Xr rnd 9
.Sh HISTORY
The
.Nm
program was first made available in
.Nx 1.3 .
.Sh AUTHORS
The
.Nm
program was written by
.An Michael Graff
.Aq explorer@flame.org .