Unikernels — single purpose, lightweight virtual machines — have been discussed at several past QCons. These talks have provided an overview of the capabilities of various unikernel systems. In addition, at last year’s QConSF, I discussed a broad range of projects for which we have used unikernels, but only discussed each at a high level.

In this talk, rather than taking a broad look at the technology, we will take a deep dive into a unikernel implementation of the Tor anonymity system. We’ll discuss what aspects of Tor make it an attractive target for a unikernel, and what aspects of unikernels are particularly interesting when considering Tor. We’ll then look at what it took to build our Tor unikernel, and what actual challenges developers will face when implementing real-world systems. We’ll conclude with a basic comparison between our Haskell implementation of Tor and the mainline revision, and consider what challenges remain in the effort.