1.\" 2.\" SPDX-License-Identifier: BSD-2-Clause 3.\" 4.\" Copyright (c) 2023 Fernando Apesteguia <fernando.apesteguia@gmail.com> 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.Dd September 18, 2023 28.Dt SAVE-ENTROPY 8 29.Os 30.Sh NAME 31.Nm save-entropy 32.Nd Save bits of entropy to feed /dev/random at startup 33.Sh SYNOPSIS 34.Nm save-entropy 35.Sh DESCRIPTION 36The 37.Nm 38command is used to save entropy data from 39.Pa /dev/random 40to files in a specified output location. 41The files saved are used at startup to provide additional entropy for 42.Pa /dev/random . 43The output file will be different in every invocation until the maximum number 44of different files is reached. 45(See 46.Em entropy_save_num 47for details). 48By default this script is invoked via 49.Xr cron 8 50every eleven minutes approximately. 51.Pp 52This command does nothing if executed inside a 53.Xr jail 8 . 54.Pp 55Three variables in 56.Pa /etc/rc.conf 57regulate the behavior of the script: 58.Bl -tag -width Ds 59.It Va entropy_dir 60Specify the directory for saved entropy files. 61Defaults to 62.Pa /var/db/entropy . 63If set to "NO" it disables caching entropy via 64.Xr cron 8 . 65This setting is shared with 66.Pa /etc/rc.d/random . 67.It Va entropy_save_sz 68Size of the entropy cache files. 69Defaults to 4096. 70.It Va entropy_save_num 71Number of entropy cache files to save. 72Defaults to 8. 73.El 74.Sh FILES 75.Bl -tag -width Ds 76.It Pa /etc/rc.conf 77.El 78.Sh EXIT STATUS 79.Ex -std 80Errors will be recorded in the system log. 81.Sh SEE ALSO 82.Xr syslog 3 , 83.Xr random 4 , 84.Xr rc.conf 5 , 85.Xr cron 8 86.Sh HISTORY 87The 88.Nm 89command first appeared in 90.Fx 5.0 . 91.Sh AUTHORS 92The 93.Nm 94command was originally written by 95.An Doug Barton <dougb@FreeBSD.org> . 96This manual page was written by 97.An Fernando Apesteguia <fernape@FreeBSD.org> . 98