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Increasing the entropy in virtual machines

Access to high-quality random numbers is important for the proper functioning of an operating system, in particular for its security related components and applications. In case the rate by which /dev/random provides random numbers within a VM is not sufficient, users can install
the rngd service to generate random numbers from the underlying processor's Digital Random Number Generator (DRNG):

$ yum install -y rng-tools
$ systemctl start rngd

This will increase the rate at which random numbers are available from /dev/random, but avoid the lower-quality pseudo-random numbers from /dev/urandom.

More information on rngd can be found in the RedHat Security guides for CC7 / RHEL7.

At the moment, the CERN cloud service does not configure the export of random numbers from the host to the guests (as implemented by the virtio_rng driver, for instance).

Last update: September 14, 2021