---
name: "save-entropy"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/save-entropy"
---

# save-entropy(8)

Save bits of entropy to feed /dev/random at startup

## NAME

**save-entropy** – Save bits of entropy to feed /dev/random at startup

## SYNOPSIS

**save-entropy**

## DESCRIPTION

The **save-entropy** command is used to save entropy data from */dev/random* to files in a specified output location. The files saved are used at startup to provide additional entropy for */dev/random*. The output file will be different in every invocation until the maximum number of different files is reached. (See *entropy\_save\_num* for details). By default this script is invoked via [cron(8)](/cron/8.md) every eleven minutes approximately.

This command does nothing if executed inside a [jail(8)](/jail/8.md).

Three variables in */etc/rc.conf* regulate the behavior of the script:

- *entropy\_dir*

  Specify the directory for saved entropy files. Defaults to */var/db/entropy*. If set to "NO" it disables caching entropy via [cron(8)](/cron/8.md). This setting is shared with */etc/rc.d/random*.

- *entropy\_save\_sz*

  Size of the entropy cache files. Defaults to 4096.

- *entropy\_save\_num*

  Number of entropy cache files to save. Defaults to 8.

## FILES

- */etc/rc.conf*

  ## EXIT STATUS

The **save-entropy** utility exits 0 on success, and \>0 if an error occurs. Errors will be recorded in the system log.

## SEE ALSO

[syslog(3)](/syslog/3.md), [random(4)](/random/4.md), [rc.conf(5)](/rc.conf/5.md), [cron(8)](/cron/8.md)

## HISTORY

The **save-entropy** command first appeared in FreeBSD 5.0.

## AUTHORS

The **save-entropy** command was originally written by Doug Barton \<dougb@FreeBSD.org\>. This manual page was written by Fernando Apesteguia \<fernape@FreeBSD.org\>.