1. UNIX/LINUX Introduction
Copyright © 2017 – Curt Hill

2. UNIX Developed by Bell Labs around 1972 Simplified MULTICS
Software development system
Simplified MULTICS
An OS and project from which Bell Labs withdrew
C was designed so that UNIX could be written in something other than assembly
Without question the most influential OS yet
Many varieties of UNIX and LINUX
Copyright © 2017 – Curt Hill

3. Features Multi-user and multi-tasking Tree shaped directory
Command processor is termed a shell
Commands are just executables
Commands allow file redirection, file pipes and concurrency
Many of these features were first or very early in UNIX
Copyright © 2017 – Curt Hill

4. History Before and after 1972 most OSs were proprietary
In Assembly or proprietary languages
Source code was often distributed to installation with strong non-disclosure restrictions
Usually could only used on one class of machine
IBM was dominant with approximately 75% of the market
Copyright © 2017 – Curt Hill

5. MULTICS Joint project of several manufacturers
Perhaps MULTICS was the most influential OS, since it strongly influenced UNIX
However, it grew too large to be used on anything but a substantial mainframe
Bell Labs pulled out, probably because it did not fit their business model
More interested in smaller OSs for smaller machines
Copyright © 2017 – Curt Hill

6. The Gang
A number of people believed that an OS can be powerful and yet small
Ritchie, Kernighan, Plauger among others
Dennis Ritchie writes the first C compiler so that they could do the job in C rather than assembly
Then it requires half the effort or less
The first UNIX is research project
Only used at Bell Labs
Copyright © 2017 – Curt Hill

7. Philosophy The gang never thought of themselves as OS maintainers
They provided the basic features but allowed nearly anyone to improve their code
Everyone could obtain any piece of source code
If they could improve the code they did so
They then convinced the system administrator to make it the standard
Word got out
Copyright © 2017 – Curt Hill

8. GNU A movement starts that provides alternatives to UNIX commands: GNU
Good Not UNIX
Many of these improved codes are distributed through them as Open Source
GNU is part of the Free Software Foundation
Copyright © 2017 – Curt Hill

9. Escape Bell Labs is largely a research center
They think of themselves as a private research university without students
The corporation wants to see usable prototypes developed, but does pure research
There are no plans to market UNIX
The researchers start giving it to others
Usually universities
Later businesses as well
Copyright © 2017 – Curt Hill

10. Variants
Each computer manufacturer and some others customize their copy and start distributing it
IBM – AIX
HP – HPUX
Sun – Solaris
Berkeley – BSD
Copyright © 2017 – Curt Hill

11. Recapture ATT realizes that others are making money off of their work
Some of these are in competition in some markets
They assert that everybody should pay them royalties
Most business pay up because it is fair
They have made money off it
ATT is also the largest company on the planet at the time
Copyright © 2017 – Curt Hill

12. Renegades Two groups react negatively
University of California at Berkley
Linus Torvalds
Copyright © 2017 – Curt Hill

13. Berkeley Berkeley has put a lot of effort into their version
They have not made any money on it, nor do they intend to market it
Neither have they signed any kind of non-disclosure or non-distribution agreement
Much of the fairness argument of ATT just does not fly for their case
They file suit
Copyright © 2017 – Curt Hill

14. Conclusion of the Suit Berkeley wins
There are now two independent UNIXs
System V from ATT
BSD from Berkeley
Copyright © 2017 – Curt Hill

15. Linus Torvalds
Linus recognizes that the kernel is the only part that could ever be copyrighted
Everything above that was written elsewhere or could be replaced , such as by GNU or by others
He decides to write a different kernel as a summer project
Takes a little longer than that
This occurs while ATT and Berkeley are litigating
Copyright © 2017 – Curt Hill

16. LINUX Kernel Linus names his new kernel LINUX
After himself
This kernel takes the same APIs as original with completely different underlying code
Compare with Oracle suit against Google
He makes it open source
Copyright © 2017 – Curt Hill

17. The UNIX Family Tree
Copyright © Curt Hill

18. Importance of UNIX/LINUX
Several things have contributed to the impact
It is open source
It is very old
Many of the original bugs have been removed
Most features that are desirable have been added
Its original small approach makes it efficient
Has not suffered commercial bloat
Copyright © 2017 – Curt Hill

19. Commands
The UNIX command-line is always provided by one or another shell
Bourne shell (sh)
C shell (csh)
BASH (from GNU)
Korn Shell
Among others
Similarly, there are multiple GUI interfaces, generically called XWindows
Gnome
Copyright © 2017 – Curt Hill

20. Servers
Generally some flavor of UNIX/LINUX is the preferred OS for servers
Usually free and open source
Performs well
Large group of people generating usable code for it
Most of the networking utilities were first constructed for UNIX
Copyright © 2017 – Curt Hill

21. File System UNIX popularized the tree-shaped directory system
Files may be either ordinary or directories
Any directory may have other directories or files in it
Unlike the MicroSoft OS convention a forward slash delimits directories
An initial slash starts at the root directory
Copyright © 2017 – Curt Hill

22. Devices MS copied the basic form of DOS from CPM
This includes device latters
After DOS 1 they largely copy features from UNIX
A mount point is a name that indicates the root of a new device
Thus the / is the root of the entire file system
Copyright © 2017 – Curt Hill

23. Relative directories
MS copied the UNIX convention for relative directories
One dot says this directory
Two dots says the previous
Copyright © 2017 – Curt Hill

24. Directory information
Each file has several dates:
Creation time and date
Last change
Last access
It also indicates an owner and a group
It had nine permission bits
Read, write and execute
One set for owner, group and world
Copyright © 2017 – Curt Hill

25. Home pages UNIX was always a multi-user system
Shared and system files were generally near the root in common directories
There was also a usr directory which generally housed all the user’s local space
Each user received a directory in usr which is named for their login
They created directories and files in that
Copyright © 2017 – Curt Hill

26. Finally Learning command line UNIX/LINUX should not be that hard
Once we have this background
There are a large number of commands that will be considered in another presentation
Copyright © 2017 – Curt Hill