Updated: 2021/Feb/13


RNDCTL(8)                   System Manager's Manual                  RNDCTL(8)

NAME
     rndctl - kernel entropy pool management tool

SYNOPSIS
     rndctl [-CcEe] [-d devname | -t devtype]
     rndctl [-lsv] [-d devname | -t devtype]
     rndctl [-i] -L save-file
     rndctl -S save-file

DESCRIPTION
     The rndctl program displays statistics on the current state of the rnd(4)
     device, and controls which sources are allowed to contribute to the
     entropy pool maintained by rnd(4).

     The following options are available:

     -C      Disable collection of timing information for the given device
             name or device type.

     -c      Enable collection of timing information for the given device name
             or device type.

     -d      Only the device named devname is altered or displayed.  This is
             mutually exclusive with -t.

     -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.

     -e      Enable entropy estimation using the collected timing information
             for the given device name or device type.

     -i      With the -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 /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.

     -L      Load saved entropy from file save-file and overwrite it with a
             seed derived by hashing it together with output from /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.

     -l      List all sources, or, if the -t or -d flags are specified, only
             those specified by the devtype or devname specified.

     -S      Save entropy pool to file save-file.  The file format is specific
             to rndctl and includes an estimate of the amount of saved entropy
             and a checksum.

     -s      Display statistics on the current state of the entropy pool.

     -t      All devices of type devtype are altered or displayed.  This is
             mutually exclusive with -d.

             The available types are:

             disk   Physical hard drives.

             net    Network interfaces.

             tape   Tape devices.

             tty    Terminal, mouse, or other user input devices.

             rng    Hardware random number generators.

     -v      Verbose output.

SEE ALSO
     rnd(4), rnd(9)

HISTORY
     The rndctl program was first made available in NetBSD 1.3.

AUTHORS
     The rndctl program was written by Michael Graff <explorer@flame.org>.

NetBSD 9.99                     August 10, 2014                    NetBSD 9.99