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#!/bin/sh
### BEGIN INIT INFO
# Provides: urandom
# Required-Start: $local_fs mountvirtfs
# Required-Stop: $local_fs
# Default-Start: S
# Default-Stop: 0 6
# Short-Description: Save and restore the random seed
# Description: Save the random seed on shutdown and restore it on boot,
# to ensure that the seed isn't predicable on startup
# (because the boot process is predictable)
### END INIT INFO
test -c /dev/urandom || exit 0
RANDOM_SEED_FILE=/var/lib/urandom/random-seed
. /etc/default/rcS
[ -f /etc/default/urandom ] && . /etc/default/urandom
case "$1" in
start|"")
test "$VERBOSE" != no && echo "Initializing random number generator..."
# Load and then save 512 bytes, which is the size of the entropy
# pool. Also load the current date, in case the seed file is
# empty.
( date +%s.%N; [ -f "$RANDOM_SEED_FILE" ] && cat "$RANDOM_SEED_FILE" ) \
>/dev/urandom
rm -f "$RANDOM_SEED_FILE"
umask 077
dd if=/dev/urandom of=$RANDOM_SEED_FILE count=1 \
>/dev/null 2>&1 || echo "urandom start: failed."
umask 022
;;
stop)
# Carry a random seed from shut-down to start-up;
# see documentation in linux/drivers/char/random.c
test "$VERBOSE" != no && echo "Saving random seed..."
umask 077
dd if=/dev/urandom of=$RANDOM_SEED_FILE count=1 \
>/dev/null 2>&1 || echo "urandom stop: failed."
;;
*)
echo "Usage: urandom {start|stop}" >&2
exit 1
;;
esac
exit 0
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