This document provides an introduction to unikernels. It defines a unikernel as a specialised, single address space machine image constructed using library operating systems that can run on hypervisors, in docker containers, or directly on hardware. Unikernels are described as being small in size, fast booting, and high performance since they avoid context switches and have a minimal attack surface. Examples of unikernel implementations and applications are given, such as using unikernels for cloud computing, network functions virtualization, IoT, and high performance computing. The document then demonstrates building a simple echo web server unikernel in 5 minutes using the IncludeOS libraries and tools.

1. Look Ma’ No O.S.
An Introduction to
Unikernels
Ioannis Tsagatakis
Ioannis Stefanis
Msc in Informatics & Multimedia
Department of Informatics Engineering TEI of Crete
Embedded Systems
From bootloader to a REST API with modern C++

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What is A Unikernel
● A unikernel is a specialised, single address space
machine image constructed by using library
operating systems.
– Run on top of level 1 or 2 hypervisor
– Run in a docker container
– Run in bare metal
● Back in history (batch processing)
Single App in a single (virtual) machine

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From Apps to Unikernel Apps
● Many layers
● Many memory
transfers
● Many security
checks
● Blocking system
calls
● Dead code
● Complexity

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But Why ?
● Performance and Size
– A few kilobytes in size, Fast (really fast) boot
– High performance, No content switches
– Easy hardware /software interfaces (POSIX is hard)
● Security and Correctness
– Small attack (and «unique») surface
– No shell. So you crack my app, now what ?
● Cost effective
– Cloud is the new hardware

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Let’s write an OS
● It’s easy !
– No hardware drivers need it (almost)
● Hypervisor provides a common hardware
● Xen, Qemu, kvm
– No users, no processes, no bosses
● Single address space
● No ring levels, no boundaries, no overhead
– Multiple processes ?
– Update and deployment ?

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Implementations
● Clean State
– Mirage OS (Ocaml)
– Ling (Erlang)
– HalVM (Haskell)
– Include OS (C++)
– Solo 5
– ClickOS
● Legacy
– Osv
(Tomcat, jetty,
Cassandra ..)
– Rumprun
(MySQL, Ngingx, PHP)
– Clive (Go)
– Runtime.js
UniK

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Application Domains
● Cloud Computing
● Network Functional Virtualization (NFV)
– Decouple software from hardware
– Ericsson, NEC, Cisco
● IoT
– Build an App not a stripped OS
● Hight Prorformance Computing (HPC)
– Possible, but no implementations yet

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History
● 1990: Exokernel and Nemesis (Univ Cambridge)
● 2014: Unikernels: Rise of the Virtual Library
Operating System, ACM
● 2015: 7 Unikernel Projects to Take on Docker
● 2017: Mirage OS 3
http://unikernel.org/

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Use cases
● Cloud Computing (AWS, digital occean, ...)
– A simple static web site
– A memcached appliance
● Iot device
– Simple Web server
– REST Interface
● Custom network appliance
– In a cheap board like Raspberry Pi

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A simple echo server

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#include <os>
Demo Time
From bootloader to REST API in 5mins

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#include <XXX>
Libraries and utilities
● Acorn
– Acorn Web Server Appliance,
built with IncludeOS
● Mana
– IncludeOS C++ Web Application
Framework
● Buttler, Director
– A Mana middleware for serving
static content from a IncludeOS
drive
● Dashboard
– Dashboard back-end module for
IncludeOS Mana framework
● NaCL
● Support Libs
– Botan (TLS), cookie, http, uri,
● Bucket
– A magical bucket with the
power of storing stuff
● Unik
– The Unikernel Compilation
and Deployment Platform

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Web server demo
● Static content
● REST interface
● Memory DB
● Dashboard
$ git clone https://github.com/hioa­cs/IncludeOS
$ export INCLUDEOS_PREFIX=~/includeos/
$ export PATH=$PATH:$INCLUDEOS_PREFIX/bin
$ cd IncludeOS
$ ./install.sh
$ export CC="clang­3.8"
$ export CXX="clang++­3.8"
$ cd examples/acorm
$ boot –create­bridge .
$ xdg­open http://10.0.0.42/
Host OS -Linux (x86)
qemu (or docker)
Drivers
Include OS
& libs
App Logic
Filesystem
ROM
Memory Store
App Image
4.277K
Don’t Try this at
home

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More info
● https://github.com/hioa-cs/IncludeOS
● http://www.includeos.org/
● Google it
Let’s have thousands of self-contained,
secure micro services

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Questions ?