rndctl —
in-kernel random number generator management tool
  
    | rndctl | [ -CcEe] [-ddevname |-tdevtype] | 
  
    | rndctl | [ -lsv] [-ddevname |-tdevtype] | 
The rndctl program displays statistics on the current
  state of the rnd(4) pseudo-driver,
  and allows the administrator to control which sources are allowed to
  contribute to the randomness pool maintained by
  rnd(4), as well as whether a given
  source counts as strongly random.
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.
- -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 -tor-dflags 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 rndctland includes an estimate of
      the amount of saved entropy and a checksum.
- -s
- Display statistics on the current state of the random collection
    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
- Random number generators.
 
- -v
- Verbose output: show entropy estimation statistics for each source.
  - /dev/random
- Returns “good” values only.
- /dev/urandom
- Always returns data, degenerates to a pseudo-random generator.
Therndctl program was first made available in
  NetBSD 1.3.
The rndctl program was written by
  Michael Graff ⟨explorer@flame.org⟩.
Turning on entropy estimation from unsafe or predictable sources will weaken
  system security, while turning on entropy collection from such sources may
  weaken system security.
Care should be taken when using this command.