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RNGD(8)								       RNGD(8)

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

SYNOPSIS
       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]

DESCRIPTION
       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

OPTIONS
       -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‐
	      dom)

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

       -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
	      bits).

       -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

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

rng-tools 2			  March 2001			       RNGD(8)

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