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OS Motivation

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IT Systems, Summer Term 2024
Dr. Jens Lechtenbörger (License Information)

1. Introduction

1.1. Learning Objectives

  • Discuss role of OSs to control computers
    • Performance aspects
    • Ownership and control
  • Discuss role of licenses to control software

1.2. Performance Aspects

  • OS manages computer’s resources: CPU, memory, I/O
  • OS understanding helps to identify and reason about resource bottlenecks.
    • Improve design, analysis, and implementation of information systems.
    • E.g., why is my computer/application slow? How to improve that?
  • (Above are “traditional” topics for OS courses; this presentation takes a different direction.)

1.3. Whom do Computers Obey?

  • So far, you learned how to build a computer.
    • How does that feel?
  • Next, we investigate Operating Systems (OSs) to control computers.


    Search” under CC0 1.0; from Pixabay

    • OS controls what is executing when.
    • Who controls the OS?
    • Who controls the computer, then?

1.4. Computers


Server” under CC0 1.0; cropped from Pixabay


C64” under CC0 1.0; from Pixabay


Notebook” under CC0 1.0; from Pixabay


Router” under CC0 1.0; from Pixabay


Car” under CC0 1.0; from Pixabay


Doll” under CC0 1.0; from Pixabay


TV” under CC0 1.0; from Pixabay

Smart watch

Smart watch” under CC0 1.0; cropped from Pixabay

Fairphone 2

Fairphone 2” by Kaihsu Tai under CC BY-SA 4.0; cropped from Wikimedia Commons

1.5. Enlightenment

Enlightenment is man’s emergence from his self-incurred immaturity. (Immanuel Kant, 1784)

  • Self-incurred immaturity
    • You let someone else decide and speak for you
    • Here: Someone else programs your computer beyond your control
  • Emergence

    Brain training

    Brain training” by Shocho under CC BY 3.0 US; cropped from the Noun Project

    • You speak for yourself
    • Here: You choose controllable programming for your computer

2. Choices and Consequences

2.1. Impact of Choices

  • Economic and ecological/social impact

    Man with megaphone

    Man with megaphone” under CC0 1.0; from Pixabay

    • What do you buy/use/create?
      • What do you advertise?
      • What do you impose on others?
  • Economic impact
    • Should be obvious
  • Ecological/social impact

    Magnet attracting people

    Figure” under CC0 1.0; from Pixabay

    • If you use some social/communication service, you increase its appeal and value
    • If you choose communication under surveillance capitalism or attention economy, you impose their mechanisms on your family, friends, colleagues …

2.2. Rationale

  • Ownership of smart devices requires control over software

2.2.1. Sample Lecturer’s Choices

  • Smartphone running GrapheneOS
    • No Google “services” required (but possible)
    • F-Droid as app store
    • With preference for offline functionality
  • Before buying a smartwatch with health tracking, make sure that Gadgetbridge supports it
    • Sensitive data does not flow to vendor’s servers (as with default app)
    • No “cloud API” whose shutdown bricks the device
  • Kickstarter for Volla tablet

3. Software

3.1. Free Software

3.2. Free vs Open Source

  • Mostly philosophical distinction, sometimes religious
    • I prefer the term “free software” because it emphasizes freedom
    • If you do not want your academic works (theses, code, project results) to disappear, publish them under free licenses

3.3. GNU/Linux

  • Tux, the Linux mascot

    Tux, the Linux mascot” under CC0 1.0; from Wikimedia Commons

    • I encourage you to try out GNU/Linux, which is free software,
      • the major OS for cloud infrastructures,
      • the server OS in lots of project seminars.
    • Upcoming assignments are based on GNU/Linux
      • Several GNU/Linux distributions can be started as live systems from CD/DVD or USB stick without changing your current installation

3.4. Firmware

  • Firmware = Software that is embedded in hardware by vendor
    • Stored in (EP)ROM, flash
    • Initialization and control of hardware
      • E.g., BIOS, (U)EFI; but also video BIOS of graphics card, Management Engine of Intel CPUs
        • Typically shipped as binary blobs
        • NSA ANT catalog also contains firmware trojans (in wake of Snowden revelations)

3.4.1. CPU Rings

  • Outlook: CPUs have rings/privilege levels
    • Instruction set restricted depending on ring
      • Ring 3: User mode for programs (I/O and memory access restricted)
      • Ring 2, 1: Usually unused (originally for system services and device drivers)
      • Ring 0: Kernel mode for OS (traditionally, ring 0 was most privileged)
      • More rings (Frazelle 2019)
        • Ring -1: Hypervisor (virtual machine monitor)
        • Ring -2: System management mode (SMM), unified extensible firmware interface (UEFI)
        • Ring -3: Management Engine

3.4.2. Free and Open Firmware

  • Articles by Jessie Frazelle
    • (Frazelle 2019)
      • “Between Ring -2 and Ring -3 there are at least two and a half other kernels in our stack that have many capabilities. Each of these kernels has its own networking stacks and web servers, which is unnecessary and potentially dangerous, especially if you do not want these rings reaching out over the network to update themselves. The code can also modify itself and persist across power cycles and reinstalls. There is very little visibility into what the code in these rings is actually doing, which is horrifying, considering these rings have the most privileges.”
    • (Frazelle 2020a)
      • “It’s an alarming problem that the code running with the most privilege has the least visibility and inspectability.”
    • (Frazelle 2020b)
      • “If you would like to help with the open source firmware movement, push back on your vendors and platforms you are using to make their firmware open source.”

4. Conclusions

4.1. Summary

  • Do you care?


Frazelle, Jessie. 2019. “Open Source Firmware.” Commun. Acm 62 (10): 34–38.
———. 2020a. “Opening up the Baseboard Management Controller.” Commun. Acm 63 (2): 38–40.
———. 2020b. “Securing the Boot Process.” Commun. Acm 63 (3): 38–42.

License Information

Source files are available on GitLab (check out embedded submodules) under free licenses. Icons of custom controls are by @fontawesome, released under CC BY 4.0.

Except where otherwise noted, the work “OS Motivation”, © 2018-2024 Jens Lechtenbörger, is published under the Creative Commons license CC BY-SA 4.0.