RNGD(8)                                                                RNGD(8)


       rngd - Check and feed random data from hardware device to kernel random


       rngd [-b, --background] [-f, --foreground]  [-o,  --random-device=file]
       [-r,  --rng-device=file]  [-s,  --random-step=nnn]  [-W,  --fill-water-
       mark=nnn] [-t, --timeout=nnn] [-?, --help] [-V, --version]


       This daemon feeds data from a random number generator to  the  kernel’s
       random  number  entropy  pool,  after first checking the data to ensure
       that it is properly random.

       The -f or --foreground options can be used to tell rngd to avoid  fork-
       ing  on  startup.   This  is  typically  used for debugging.  The -f or
       --foreground options, which fork and put rngd into the background auto-
       matically, are the default.

       The  -r  or  --rng-device  options  can  be used to select an alternate
       source of input, besides the default /dev/hwrandom.  The -o  or  --ran-
       dom-device  options  can  be used to select an alternate entropy output
       device, besides the default /dev/random.  Note that  this  device  must
       support the Linux kernel /dev/random ioctl API.

       FIXME: document random-step and timeout


       -b, --background
              Become a daemon (default)

       -f, --foreground
              Do not fork and become a daemon

       -o file, --random-device=file
              Kernel  device used for random number output (default: /dev/ran-

       -r file, --rng-device=file
              Kernel device used for random number input (default: /dev/hwran-

       -s nnn, --random-step=nnn
              Number of bytes written to random-device at a time (default: 64)

       -W n, --fill-watermark=nnn
              Once we start doing it, feed entropy to random-device  until  at
              least  fill-watermark  bits  of  entropy  are  available  in its
              entropy pool (default: 2048).  Setting this too high will  cause
              rngd  to  dominate the contents of the entropy pool.  Low values
              will hurt system performance during entropy starves.  Do not set
              fill-watermark  above the size of the entropy pool (usually 4096

       -t nnn, --timeout=nnn
              Interval written to random-device when the entropy pool is full,
              in seconds, or 0 to disable (default: 60)

       -?, --help
              Give a short summary of all program options.

       -V, --version
              Print program version


       Philipp Rumpf
       Jeff Garzik - jgarzik@pobox.com
       Matt Sottek

rng-tools 2                       March 2001                           RNGD(8)

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