CS 111 - Operating Systems Principles

      Assembled by: Jeremy Ir, Charles Rudolph, Song Zheng

Lecture 1: Tuesday, March 30, 2010

Assigned Reading: Sections 1 to 2.3

Course Overview

Textbook: Jerome H. Saltzer and M. Frans Kaashoek, Principles of Computer System Design: An Introduction
                    - Systems book, not OS book, very big picture, not enough OS details

Course Website:   http://cs.ucla.edu/classes/spring10/cs111

Course Organization:

• 19 Lectures
• Midterm, 100 min, Thursday of 5th Week (subject to change)
• Final Exam, 180 min, date and location based on registar
• 4 Labs (1a, 1b, 2, 3, 4) – may work in pairs or alone
• 2 Minilabs
• Design Problem (oral presentation, written report)
• 1-page report
• Scribe notes, in HTML 4.0.1, due a week after lecture (faster turnaround required near midterm and final)

Resources for Labs:

• OS Seasnet Labs
• Seasnet Linux Servers
  • lnxsrv01.seas.ucla.edu, lnxsrv02.seas.ucla.edu, lnxsrv03.seas.ucla.edu
  • add "/usr/local/cs/bin" to your path
• UCLA Linux Users Group
• Emulators – QEMU, Bosch

Grading Policy:

• 1/3 - Exams
  • 2/9 – Final
  • 1/9 – Midterm
• 1/3 - Labs
  • 1/12 – Each lab (4)
• 1/3 - Other
  • 1/15 – Each minilab (2)
  • 1/12 – Design problem
  • 1/12 – Scribe
  • 1/30 – 1-page report

***Lateness policy, lose one letter grade per day, 3 free late days

Definitions

What’s a system?

• Oxford English Dictionary (1928)
  • organized or connected group of objects
  • set of principles, etc. a scheme, a method
  • From Greek word σύστημα:
    • organized whole, government, constitution
    • a body of people or animals
    • musical interval
    • a group of connected verses in a poem
  • roots are “set up with”

What’s an operating system?

• American Heritage Dictionary (2000)
  • Software designed to control the hardware of a specific data processing system in order to allow users and application programs to make use of it
• Encarta (2007)
  • Master control program in a computer
• Wikipedia (11934131)
  • Set of computer programs that manage the hardware and software resources of a compute
• Definitions from the class
  • OS = optional GUI (may be separate application) + Library (helpful existing code) + Interface to lower level hardware facilities
• Book
  • System is a set of interconnected components that has a specified behavior at the interface with its environment
  • Systems nest(compoents in system)
    
  • Example: classroom, furniture component, electrical component

Problems with Computer Systems

Incommensurate Scaling

• Not everything scales at the same rate
• Why are we 2 m tall? Scaling is a big deal
• Economies of scale (A Smith, pin factory)
  • Problems of waste
• Diseconomies of scale (star network)
  • Problems of breakage

Emergent Properties

• Arise as new, unanticipated properties in larger systems
  • Tacoma Narrows Bridge
  • Robert Morris worm of 1980s
  • Napster

Propagation of effects

• Tiny changes in part of a chaotic system can cause large changes elsewhere
• This can happen in well designed systems
• c:a\dddd\f – file name separators ( \ )
  • Japanese characters (multi-byte encoding, first byte has a leading one)
  • During parsing of a Japanese name, the back half of the multi-byte encoding is misinterpreted as a file name separator
  • Solutions
    • Bloat kernel – tell it about multi-byte encoding, check for it
    • Bloat encoding – make less efficient encoding but safer

Combination Example

• Kaminsky DNS design flaw
• DNS Query, what is www.citibank.com?
• Bad guy 1 sends lots of packets, Citibank = bad address
• DNS server sends queries to a root and gets responses
  • thus bad guy 2 can send bad IP address to DNS server
  • It will return the IP address to any user that asks for it
  
  

• Incommensurate Scaling of bad guys
• Emergent Properties of attacking DNS server
• Propagation of Effects can forge return address of packets

COMPLEXITY

• New to computer systems
• Because: Moores Law
  • Number of transistors doubles every two years
  • Number of transistors keeps going up, complexity keeps rising
  
  
  
• Because: Kryder's Law
  • Disk Drive Capacity
  • Easier for us to design more complex systems