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  • 1. System & Network Administration
    • Chapter 0 – Introduction
    • Chapter 1 – Desktops
    • By Chang-Sheng Chen (20080218)
  • 2. The Practice of System and Network Administration
    • Components of the book
      • Part 1: The Principles
      • Part 2: The Processes
      • Part 3: The Practices
      • Part 4: Management
    • The Editing Style of each chapter
      • The Basics
      • The Icing
  • 3. System Administration Tasks
    • A Typical Life Cycle of SA Tasks
      • Identification/Definition Phase
        • Collecting information
        • Analysis
      • Design Phase
      • Deployment Phase
        • Installation, Configuration
      • Maintenance Phase
        • Update
        • Debug/Troubleshooting
        • Reconfiguration, Rebuild
  • 4. Contents of Chapter 0 - Introduction
    • I.1 Do These Now !
      • Use a Trouble-Tick System
      • Manage Quick Requests Right
      • Start Every New Host in a Known State
    • I.2 Conclusion
  • 5. Contents of Chapter 1
    • 1.1 The Basics
      • 1.1.1 Loading the System Software and Applications initially
      • 1.1.2 Updating the System Software and Applications
      • 1.1.3 Network Configuration
      • 1.1.4 Dynamic DNS with DHCP
    • 1.2 The Icing
      • 1.2.1 High Confidence in Completion
      • 1.2.2 Involve customers in the Standarization Process
      • 1.2.3 A Variety of Standard Configurations
    • 1.3 Conclusion
  • 6. Desktops
    • Desktops are usually deployed in large quantities and in long life cycles .
    • The Big Three Tasks of managing operations systems on Desktops
      • Loading the system software and applications initially
      • Updating the system and applications
      • Configuring network parameters
    • Automating these tasks makes a world of difference
  • 7. Desktops - The Basics
    • Managing operations systems on Desktops
      • Loading the system software and applications initially
      • Updating the system and applications
      • Configuring network parameters
    • Evard’s life cycle of a machine (Evard 1997)
    • Automating Installation Reduces Frustration
    • First-class Citizens (i.e., Fully-support)
      • A variety of platforms
  • 8. Evard’s life cycle of a machine ( LISA XI, Evard 1997)
  • 9. What can we learn from the diagram in previous page ?
    • 1. Various states and transitions exists.
      • Plan for installation, things will break and require repair , etc .
    • 2. The computer is usable only in the configured state.
      • We want to maximize the amount of time spent in that state.
        • The setup and recovery process should be fast, efficient, and automated.
        • Ensure that the OS degrades as slowly as possible .
          • Design decisions by the vendor have the biggest impacts
          • Architecture decisions by the SA can weaken the protection
  • 10. What can we learn from the diagram in previous page ? (Cont.)
    • 3. When mistakes are made during installation, the host will start into a decay cycle .
    • 4. Reinstallation (rebuild) is similar to installation, except one may potentially have to carry forward old data and applications .
    • 5. Finally, machines are eventually retired.
      • Some data and applications must be carried to the replacement machine or stored on the tape for future reference.
  • 11. Updating the system software and Applications
    • Updates are different from the Initial Load
      • The host is in usable state (vs. disabled state)
      • The host is in an office
      • No physical access
      • The host is already in use
        • Cannot be messed up after the update/patches
      • The host may not in “known state”
      • The host may have “live” users (e.g., log in and still running active programs)
      • The host may be gone (e.g., not booted temporarily).
      • The host may be dual-boot (e.g., Windows + Linux, or even multi-boot,)
  • 12. Updating the system software and Applications
    • Characteristic:
      • An automated update system has potential to cause massive damage.
      • Use the One-Some-Many technique to reduce the risk of a failed patch.
        • One -> Some -> Many
    • Tips for guiding the update process
      • Create a well-defined update that will be distributed to all hosts.
      • Establish a communication plan so that those affected do not feel surprised by updates.
      • Checkpoints and restart
        • If there is a single failure , the group size returns to a single host and starting growing again.
      • Needing a way for customers to stop the deployment process if things go disastrously wrong.
  • 13. DHCP
    • Dynamic DNS with DHCP
      • Adds unnecessary complexity and security risks
      • Letting a host determine its own hostname is a security risk (e.g., conflicting names)
      • Workaround: Dynamic DNS should be limited to specific DNS zones (i.e., building a “jail” for dynamic DNS configuration)
    • Advantages of Using DHCP
      • Avoiding situations in which the customers are put into a position that allow their simple mistakes to disrupt others.
        • E.g., The same IP address as a router (default gateway)
      • Managing DHCP Lease Time
        • Lease time can be managed to aid in propagating updates. (e.g., Change subnet netmask)
      • DHCP Also assists in Moving Clients away from Resources (e.g., Changing IP address of a DNS server)
  • 14. Network Configuration
    • DHCP (Dynamic Host Configuration Protocol)
      • The most common system to automating ways to update network parameters for a large desktop environment
    • Use Template Rather Than Per-Host Configuration
    • When to Use Dynamic Lease
      • When you have many hosts chasing a small number of IP address
        • Cf. Office LANs  statically assigned
        • Servers -> static assignment (permanent lease)
    • DHCP and Public Network
      • LANs in university labs or dorms, hotel rooms, wireless LANs, etc.
  • 15. 1.2 The Icing
    • High confidence in Completion
      • automation
    • Involve Customers in the Standardization Process
      • Platform controlled by management (i.e., specific AP sites, telesales offices, etc.)
      • Platforms controlled by SA Team (more common)
        • Base system, most commonly required applications, utilities that can be licensed economy in bulk
    • A Variety of Standard Configurations
      • Beauty or nightmare ?
        • Simple (all the same) and scalability (multiple configuration schemes)
  • 16. Appendix
    • Background - Internet Applications
    • Networking Troubleshooting Process
    • 5 Phases of Software Life Cycle
    • DNS security and DHCP
    • Case Study: E-mail delivery errors of NCTU-course portal
  • 17. Background - Internet Applications
  • 18. Networking Troubleshooting Process DNS_b DNS_a SMTP_a SMTP_b DNS Filtering DNS Filtering Router/Switch Filtering Router/Switch Filtering SMTP Filtering SMTP Filtering Client Router_a Router_b
  • 19. 5 Phases of Software Life Cycle Waterfall Model
  • 20. 5 Phases of Software Life Cycle Realistic Waterfall Model
  • 21. Local Attacks (1) DNS spoofing HOST DNS MITM If the attacker is able to sniff the ID of the DNS request , he/she can reply before the real DNS server serverX.localdomain.it 10.1.1.50 10.1.1.1
  • 22. Local Attacks (2) DNS spoofing - tools
    • Ettercap ( http://ettercap.sf.net )
      • Phantom plugin
    • Dsniff ( http://www.monkey.org/~dugsong/dsniff )
      • Dnsspoof
    • Zodiac ( http://www.packetfactory.com/ Projects / zodiac )
  • 23. Local to remote attacks (1) DHCP/DNS spoofing
    • The DHCP request are made in broadcast .
    • If the attacker replies before the real DHCP server it can manipulate :
      • IP address of the victim
      • GW address assigned to the victim
      • DNS address
  • 24. Local to remote attacks (2) DHCP spoofing - countermeasures
    • YES - detection of multiple DHCP replies
    • Yes – restrict the DHCP replies to a range of IP
      • e.g., discard the DHCP replies from remote sites across edge routers since they can be spoofed
  • 25.  
  • 26.  
  • 27. Viewing Header Source of a Mail Messages
  • 28. Excerption of The SMTP System Log
    • Sep 13 12:43:31 mail sm-mta[1868]: k8D4hUEP001868: from=<cschen@mail.nctu.edu.tw>, size=4154, class=0, nrcpts=3, msgid=<45078D1E.9060906@mail.nctu.edu.tw>, proto=ESMTP, daemon=MTA, relay=C200-152.cc.NCTU.edu.tw [140.113.200.152]
    • Sep 13 12:43:31 mail sm-mta[1870]: k8D4hUEP001868: to=<cschen@mail.nctu.edu.tw>, ctladdr=<cschen@mail.nctu.edu.tw> (1002/20), delay=00:00:00, xdelay=00:00:00, mailer=local, pri=94461, relay=local, dsn=2.0.0, stat=Sent
    • Sep 13 12:43:33 mail sm-mta[1870]: k8D4hUEP001868: to=<n0170@infor.org>, ctladdr=<cschen@mail.nctu.edu.tw> (1002/20), delay=00:00:02, xdelay=00:00:02, mailer=esmtp, pri=94461, relay=athena.infor.org. [203.64.26.200], dsn=2.0.0, stat=Sent (Ok: queued as A6EA617029)
    • Sep 13 12:43:34 mail sm-mta[1870]: k8D4hUEP001868: to=<leafmab.csie93@nctu.edu.tw>, ctladdr=<cschen@mail.nctu.edu.tw> (1002/20), delay=00:00:03, xdelay=00:00:01, mailer=esmtp, pri=94461, relay=d2-spool.ntcu.net. [211.76.241.2], dsn=2.0.0, stat=Sent (Ok: queued as EC8D419EF4)

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