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f45b195302
git-svn-id: svn://svn.linuxfromscratch.org/BLFS/trunk/BOOK@3 af4574ff-66df-0310-9fd7-8a98e5e911e0
69 lines
2.3 KiB
XML
69 lines
2.3 KiB
XML
<sect1 id="postlfs-config-random" xreflabel="random">
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<?dbhtml filename="random.html" dir="postlfs"?>
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<title>Random number generation</title>
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<para>The Linux kernel supplies a random number generator which is accessed
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through <filename>/dev/random</filename> and
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<filename>/dev/urandom</filename>. Programs that utilize the random and
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urandom devices, such as OpenSSH, will benefit from these instructions.</para>
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<para>When a Linux system starts up without much operator interaction, the
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entropy pool, data used to compute a random number, may be in a fairly
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predictable state. This creates the real possibility that the number generated
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at startup may always be the same. In order to counteract this effect,
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you should carry the entropy pool information across your shut-downs and
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start-ups. The following init.d script and links will perform this function
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for you automatically.</para>
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<para><screen><userinput>cat > /etc/rc.d/init.d/random << "EOF"
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</userinput>
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#!/bin/sh
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# Begin $rc_base/init.d/random
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# Based on sysklogd script from LFS-3.1 and earlier.
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# Rewritten by Gerard Beekmans - gerard@linuxfromscratch.org
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# Random script elements by Larry Lawrence
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source /etc/sysconfig/rc
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source $rc_functions
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case "$1" in
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start)
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echo "Initializing kernel random number generator..."
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if [ -f /var/tmp/random-seed ]; then
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cat /var/tmp/random-seed >/dev/urandom
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fi
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dd if=/dev/urandom of=/var/tmp/random-seed count=1 &>/dev/null
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evaluate_retval
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;;
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stop)
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echo "Saving random seed..."
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dd if=/dev/urandom of=/var/tmp/random-seed count=1 &>/dev/null
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evaluate_retval
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;;
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*)
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echo "Usage: $0 {start|stop}"
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exit 1
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;;
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esac
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# End $rc_base/init.d/random
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<userinput>EOF
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chmod 755 /etc/rc.d/init.d/random</userinput></screen></para>
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<para>Create the symbolic links to this file in the relevant rc.d directories
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with the following commands:
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<screen><userinput>cd /etc/rc.d/init.d &&
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ln -sf ../init.d/random ../rc0.d/K45random &&
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ln -sf ../init.d/random ../rc2.d/S25random &&
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ln -sf ../init.d/random ../rc3.d/S25random &&
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ln -sf ../init.d/random ../rc4.d/S25random &&
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ln -sf ../init.d/random ../rc5.d/S25random &&
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ln -sf ../init.d/random ../rc6.d/K45random</userinput></screen></para>
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</sect1>
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