Resposta adaptada do SuperUser: link
Tudo o que você precisa fazer é criar algo como /etc/udev/rules.d/70-harware-randomizer-enable.rules
com o seguinte conteúdo:
# /etc/udev/rules.d/70-disable-random-entropy-estimation.rules
# Disables /dev/random entropy estimation (it's mostly snake oil anyway).
#
# udevd will warn that the kernel-provided name 'random' and NAME= 'ttyACM0'
# disagree. You can ignore this warning.
# Use /dev/ttyACM0 instead of /dev/random for the entropy-estimating RNG.
KERNEL=="random", NAME="ttyACM0"
# Remove any existing /dev/random, then create symlink /dev/random pointing to
# /dev/urandom
KERNEL=="urandom", PROGRAM+="/bin/rm -f /dev/random", SYMLINK+="random"