1RNGD(8)                     System Manager's Manual                    RNGD(8)
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NAME

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

11       rngd [-b, --background] [-f, --foreground] [-d, --debug]  [-l,  --list]
12       [-x,  --exclude]  [-i,  --ignorefail]  [-o,  --random-device=file] [-p,
13       --pid-file=file] [-r, --rng-device=file] [-s,  --random-step=nnn]  [-W,
14       --fill-watermark=nnn] [-q, --quiet] [-?, --help] [-V, --version]
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DESCRIPTION

18       This  daemon  feeds data from a random number generator to the kernel's
19       random number entropy pool, after first checking  the  data  to  ensure
20       that it is properly random.
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22       The  -f or --foreground options can be used to tell rngd to avoid fork‐
23       ing on startup.  This is typically  used  for  debugging.   The  -b  or
24       --background options, which fork and put rngd into the background auto‐
25       matically, are the default.
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27       The -r or --rng-device options can  be  used  to  select  an  alternate
28       source  of  input, besides the default /dev/hwrng.  The -o or --random-
29       device options can be  used  to  select  an  alternate  entropy  output
30       device,  besides  the  default /dev/random.  Note that this device must
31       support the Linux kernel /dev/random ioctl API.
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OPTIONS

34       -b, --background
35              Become a daemon (default)
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37       -f, --foreground
38              Do not fork and become a daemon
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40       -d, --debug
41              Enable debug messages
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43       -l, --list
44              List the indexes and names of available  entropy  sources.  Exit
45              code  when listing sources is 0 if at least 1 entropy source was
46              found and initialized, 1 otherwise.
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48       -x, --exclude
49              Disable entropy sources based  on  index  reported  from  --list
50              option
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52       -p file, --pid-file=file
53              File  used  for  recording  daemon  PID,  and multiple exclusion
54              (default: /var/run/rngd.pid)
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56       -i, --ignorefail
57              Ignore repeated fips failures
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59       -o file, --random-device=file
60              Kernel device used for random number output (default:  /dev/ran‐
61              dom)
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63       -r file, --rng-device=file
64              Kernel device used for random number input (default: /dev/hwrng)
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66       -s nnn, --random-step=nnn
67              Number of bytes written to random-device at a time (default: 64)
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69       -e nnn, --entropy-count=nnn
70              Number  of  bits to consider random when adding entropy. 1<=e<=8
71              (default: 8)
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73       -W n, --fill-watermark=nnn
74              Once we start doing it, feed entropy to random-device  until  at
75              least  fill-watermark  bits  of  entropy  are  available  in its
76              entropy pool.  By default, this value  is  set  to  75%  of  the
77              entropy pool size or 2048 bits if the entropy pool size couldn't
78              be determined.  Setting this too high will cause rngd  to  domi‐
79              nate  the  contents  of  the entropy pool.  Low values will hurt
80              system performance during entropy starves.   Do  not  set  fill-
81              watermark  above  the  size  of  the  entropy pool (usually 4096
82              bits).
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84       -q, --quiet
85              Suppress all messages
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87       -?, --help
88              Give a short summary of all program options.
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90       -V, --version
91              Print program version
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AUTHORS

95       Philipp Rumpf
96       Jeff Garzik - jgarzik@pobox.com
97       Matt Sottek
98       Brad Hill
99       Neil Horman - nhorman@tuxdriver.com
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103rng-tools 6                       March 2001                           RNGD(8)