It is not uncommon for people to have performance problems with the their virtual servers and chalk it up to virtualization as the problem instead of insufficient entropy. Running a mail server or SSL web server are particularly vulnerable to virtual servers without much entropy. I have noticed that my virtual servers have had a lot less entropy in the past 6 months or so. I decided to revisit what simple and effective solutions exist to solve this problem.
I decided I would do a search for debian and ubuntu packages that could be used without much modification or configuration.
- reseed – this pulls random data from random.org. However, it does this over HTTP so this package should be avoided unless one wanted to rewrite it to use HTTPS.
- randomsound – this pulls random bits from a soundcard. This is good for a host system with a soundcard but not useful for a virtual server.
- rng-tools – this is supposed to pull from a hardware true random number generator however some people have used /dev/urandom as the source. This is probably not a good solution.
- haveged – this basically uses interrupt timing to generate random numbers. Not a lot has been written about haveged but it seems like the best easily available solution. It would be nice to review the quality of the random numbers though.
- KVM supposedly has a virtio-rng device which can pull entropy from the host into the guest. This would still potentially create a need for entropy creation on the host but could be a simpler setup for those using KVM.
- It would be pretty easy to write a script to download random bits from random.org using HTTPS.