# urandom-save - save a new seed-file, for use by kernel PRNG at next boot
#

description     "save seed-file for use by kernel PRNG"

# a) We should refresh the seed-file as soon as possible
# i.e. as soon as the filesystem is mounted and writeable.
# b) We should also refresh it again as late as possible,
# i.e. when shutting down, i.e. runlevels other than 2345
start on (filesystem or runlevel [!2345])

task
console output

script
  SAVEDFILE=/var/lib/urandom/random-seed        # probably belongs in a config file
# 512 is usually the right size, as documented in drivers/char/random.c
  POOLSIZE=512                     # size in bytes
  if test -f /proc/sys/kernel/random/poolsize  \
         && ProcPoolSize="$(cat /proc/sys/kernel/random/poolsize)" ; then
# Kernels 2.6.12 and later report poolsize in bits; we convert to bytes here:
    POOLSIZE=$((ProcPoolSize/8))
  fi
  dd if=/dev/urandom of=$SAVEDFILE bs=$POOLSIZE count=1 >/dev/null 2>&1
end script