rndctl —
kernel entropy pool management tool
  
    | rndctl | [ -CcEe] [-ddevname |-tdevtype] | 
  
    | rndctl | [ -lsv] [-ddevname |-tdevtype] | 
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 data for the given device name or device type.
- -c
- Enable collection of data 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
- Ignore estimates of entropy from the drivers for the given device name or
      type.
    If collection is still enabled, data is still collected and
        mixed into the internal entropy pool, but no entropy is assumed to be
        present and data from the selected devices will not unblock
        /dev/random. 
- -e
- Accept estimates of entropy from the drivers for the given device name or
      type.
    rndctl -edoes not change the estimate
        provided by the driver; if the driver's estimate is zero, as it
        generally is for devices of types other thanrng, it remains zero afterrndctl -e.
 
- -i
- With the -Loption 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 a seed from save-file generated by
      rndctl -S. 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
- Generate a seed from the system entropy pool and save it to
      save-file for later use with rndctl
      -L.The file format is specific to rndctland includes an estimate of the amount of saved entropy and a checksum.
        The prior internal state of the system entropy pool cannot be recovered
        from save-file, so disclosure of
        save-file does not compromise past secrets drawn
        from /dev/urandom or equivalent.
 
- -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.
Therndctl program was first made available in
  NetBSD 1.3.
The rndctl program was written by
  Michael Graff ⟨explorer@flame.org⟩.