1RNGD(8) System Manager's Manual RNGD(8)
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6 rngd - Check and feed random data from hardware device to kernel random
7 device
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11 rngd [-b, --background] [-f, --foreground] [-o, --random-device=file]
12 [-r, --rng-device=file] [-s, --random-step=nnn] [-W, --fill-water‐
13 mark=nnn] [-t, --timeout=nnn] [-?, --help] [-V, --version]
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17 This daemon feeds data from a random number generator to the kernel's
18 random number entropy pool, after first checking the data to ensure
19 that it is properly random.
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21 The -f or --foreground options can be used to tell rngd to avoid fork‐
22 ing on startup. This is typically used for debugging. The -f or
23 --foreground options, which fork and put rngd into the background auto‐
24 matically, are the default.
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26 The -r or --rng-device options can be used to select an alternate
27 source of input, besides the default /dev/hwrandom. The -o or --ran‐
28 dom-device options can be used to select an alternate entropy output
29 device, besides the default /dev/random. Note that this device must
30 support the Linux kernel /dev/random ioctl API.
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32 FIXME: document random-step and timeout
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36 -b, --background
37 Become a daemon (default)
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39 -f, --foreground
40 Do not fork and become a daemon
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42 -o file, --random-device=file
43 Kernel device used for random number output (default: /dev/ran‐
44 dom)
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46 -r file, --rng-device=file
47 Kernel device used for random number input (default: /dev/hwran‐
48 dom)
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50 -s nnn, --random-step=nnn
51 Number of bytes written to random-device at a time (default: 64)
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53 -W n, --fill-watermark=nnn
54 Once we start doing it, feed entropy to random-device until at
55 least fill-watermark bits of entropy are available in its
56 entropy pool (default: 2048). Setting this too high will cause
57 rngd to dominate the contents of the entropy pool. Low values
58 will hurt system performance during entropy starves. Do not set
59 fill-watermark above the size of the entropy pool (usually 4096
60 bits).
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62 -t nnn, --timeout=nnn
63 Interval written to random-device when the entropy pool is full,
64 in seconds, or 0 to disable (default: 60)
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66 -?, --help
67 Give a short summary of all program options.
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69 -V, --version
70 Print program version
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74 Philipp Rumpf
75 Jeff Garzik - jgarzik@pobox.com
76 Matt Sottek
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81rng-tools 2 March 2001 RNGD(8)