• yum install -y gcc
• wget http://www.issihosts.com/haveged/haveged-1.9.1.tar.gz
• tar xf haveged-1.9.1.tar.gz
• cd haveged-1.9.1
• make
• ./configure
• make
• make install
• /usr/local/sbin/haveged -w 1024

To run this inside a container, you have to docker run --privileged
You can run this on host, then map /dev/random from host inside container

/!\ In test environment ONLY :

Don't install anything, just map /dev/urandom from host into /dev/random container
docker run -v /dev/urandom:/dev/random

Test entropy : (rng-tools)
cat /dev/random | rngtest -c 1000