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+---
+title: WTF is Linux
+author: Rémi Nicole <remi.nicole@smile.fr>
+date: 2020-09-08
+slide-level: 2
+aspectratio: 169
+
+theme: metropolis
+colortheme: owl
+beameroption: "show notes on second screen=right"
+
+toc: true
+highlightstyle: breezedark
+lang: en-US
+
+bibliography: ../bibliography.bib
+---
+
+# The Project
+
+## Building a Linux system manually
+
+- This is the Course (You are Here)
+- Using just normal commands
+
+::: notes
+
+Hello
+
+:::
+
+## Building a Linux system automatically
+
+- Practical Work
+- Buildroot
+
+
+## Why
+
+- Linux is everywhere in embedded software
+- Linux is everywhere in the server space
+
+
+# History
+
+## 17th century to 1970s
+
+:::: columns
+
+::: column
+![Human computer at NACA [@wikimedia:human_computer]](../res/Human Computer.jpg){ height=80% }
+:::
+::: column
+![Katherine Johnson working as a Human computer at NASA [@wikimedia:katherine_johnson_human_computer]](../res/Katherine Johnson at NASA.jpg){ height=80% }
+:::
+
+::::
+
+::: notes
+
+- NACA: National Advisory Committee for Aeronautics
+- "Computer" referred to the person that did mathematical computation
+  / verification
+- Verify trajectories for putting men into Earth orbit
+- Katherine Johnson on the right
+- You can watch the movie "Hidden Figures"
+
+:::
+
+## 1930s-1940s
+
+![Bletchley Park Bombe [@wikimedia:bletchley_park_bombe]](../res/Bletchley Park Bombe.jpg){ width=45% height=80% }
+
+::: notes
+
+- You can watch the movie "The Imitation Game"
+
+:::
+
+## 1950s
+
+::: columns
+
+:::: column
+![IBM 704 Mainframe [@wikimedia:ibm_704_mainframe]](../res/IBM 704 mainframe.jpg){ height=80% }
+::::
+
+:::: column
+![IBM 709 Mainframe [@ibm:ibm_709_mainframe]](../res/IBM 709 mainframe.jpg){ height=80% }
+::::
+
+:::
+
+::: notes
+
+- There are lights and switches
+- Back in the day, there were used to inspect and modify memory / registries or
+  see the executed instructions
+- Already two influential programming languages existed:
+        - FORTRAN (formula translation)
+        - Lisp
+- We can see:
+        - The Operator's Console
+        - The Central Processing Unit (CPU)
+        - The Punch card reader
+        - The Magnetic Tape Unit (for long term storage)
+- Very few "professional programmers"
+
+:::
+
+## 1950s---The line printer
+
+![IBM 716 Line Printer [@ibm:ibm_716_line_printer]](../res/IBM 716 line printer.jpg){ height=80% }
+
+::: notes
+
+- Really shaped the terminal as we know today
+
+:::
+
+## 1969
+
+:::: columns
+
+::: column
+
+Things were pricey:
+
+- Disk 180MB -> 32,000$
+- Commercial compiler -> 100,000$
+:::
+
+::: column
+![Boot [@needpix:boot]](../res/boot.png){ height=80% }
+:::
+
+::::
+
+::: notes
+
+- You could buy a very nice house for 32,000$
+
+:::
+
+
+## 1970s---UNIX {.allowframebreaks}
+
+![Ken Thompson (sitting) and Dennis Ritchie working together at a PDP-11 [@wikimedia:ken_thompson_dennis_ritchie]](../res/Ken Thompson and Dennis Ritchie at PDP-11.jpg){ height=67% }
+
+::: notes
+
+- He is actually coding using the teletypewriter
+
+:::
+
+\framebreak
+
+- Smaller, for one person[@fosdem:fifty_years_of_unix]
+- They actually used their own operating system
+- Invented C a bit later (1972)
+- Definitely not "free", barely "open":
+        160,000 $ per CPU
+
+Berkeley university made BSD out of it (was called Berkeley UNIX)
+
+::: notes
+
+- Targeted at big companies
+
+:::
+
+\framebreak
+
+- Same OS, different computers
+- Compiler took care of the difference in architecture.
+
+::: notes
+
+- Big advantages when compared to other solutions
+- This made UNIX popular, and by extension the C programming language too
+
+:::
+
+\framebreak
+
+Invented over the years by contributions:
+
+- shell (command interpreter)
+- pipes and filters in shell commands
+- Network file system (NFS)
+- Client/Server Windowing System
+- etc.
+
+## 1980s---GNU (Richard Stallman)
+
+1983:
+: GNU project annouced
+
+1985:
+: Created the Free Software Foundation (helps funding)
+
+1989:
+: Created GNU General Public License (GPL)
+
+Created:
+
+- Text editor (Emacs)
+- Compiler suite
+- Lots of utilities
+
+People could use these tools in different operating system
+
+::: notes
+
+- Frustrated by his printer
+- Internet was widely used in academia
+
+:::
+
+## 1990s---POSIX
+
+- Lots of different "UNIX-like" operating system existed
+- There was no proper definition of what "UNIX-like" meant
+
+## 1991--The Linux kernel (Linus Torvalds)
+
+- Just for fun
+- Needed a license
+
+::: notes
+
+- Got an Intel i386 processor for Christmas
+- Wasn't happy with the OS (he wanted page-based memory)
+- Started writing a kernel, just for fun
+- He was 21 years old
+- The current situation made it possible:
+        - Powerful "cheap" computers
+        - "Faster" internet where you could find information about operating system
+          and hardware architecture
+
+:::
+
+## 1994--Windows NT
+
+Bleurgh
+
+::: notes
+
+- Made the "personal computer" popular
+- Based on a shitty technology from IBM called DOS
+
+:::
+
+## 1990s--Linux gaining popularity
+
+- Free
+- More choice for architecture
+- Real TCP/IP stack
+
+
+::: notes
+
+- Wow, you want to connect to the internet?!
+
+:::
+
+# Command-line primer
+
+## Most commands
+
+```console
+Copies the file "file_1.txt" into "file_2.txt"
+user@host:~$ cp    file_1.txt    file_2.txt
+             ^^    ^^^^^^^^^^    ^^^^^^^^^^
+             |         |             |
+             |         '-------------'- arguments
+             |
+             '---------------------- command name (verb)
+```
+
+## The prompt
+
+```console
+ ,------ username you are logged in as
+ |
+ |        ,---- directory you are in,
+ |        |     '~' means your user directory
+vvvv      v
+user@host:~$
+     ^^^^  ^
+      |    |
+      |    '--- '$' if you are a normal user,
+      |         '#' if you are the root user
+      |
+      '--- name of the machine you are on
+```
+
+## POSIX & GNU conventions
+
+```console
+                       ,-------------- long option / flag
+                       |
+                       |           ,-- short option / flag
+                       |           |
+             vvvvvvvvvvvvvvvvvvvvv vv
+$ git commit --message="My commit" -S src/main.cpp
+  ^^^ ^^^^^^                          ^^^^^^^^^^^^
+   |    |                               |
+   |    '----------------------------- subcommand or argument
+   |
+   '---------------------------------- command name
+```
+
+# The kernel
+
+## Role
+
+Well, it depends on the kernel
+
+::: notes
+
+Some kernel are very small, some
+
+:::
+
+---
+
+![Monolithic kernel vs Microkernel](../res/OS-structure.pdf){ height=80% }
+
+## The Linux kernel
+
+- Monolithic kernel:
+  - Drivers are in the kernel
+  - File-systems (ext4, fat32, etc.) are in the kernel
+  - Lots of other things
+
+
+## Communicating with the Linux kernel
+
+- System calls
+
+::: notes
+
+- They look like functions in C code, but that's a lie, it's a hardware feature
+  using interrupts
+
+- That's it
+- Kinda
+- We can't have one system call for everything
+  - Different system calls for different types of hardware
+
+:::
+
+. . .
+
+- Everything is a file
+
+::: notes
+
+- We have special files and special file-systems
+  - They look like files, but that's a lie
+  - Reading / Writing to it does *not* read / write to storage
+  - Instead it's like calling a function of the kernel
+- Example with `/proc/cpuinfo`
+
+:::
+
+## Compiling a kernel
+
+Let's do it
+
+## Linux boot process
+
+
+```
+Boot loader
+    |
+    | loads
+    v
+Linux kernel
+    |
+    | launches
+    v
+init (first user process)
+    |
+    | does whatever it wants
+    v
+  ?????
+```
+
+::: notes
+
+- We're not going to talk about the boot loader
+- Example with `htop`
+
+:::
+
+# References