OPERATING SYSTEM

2009-09-21T02:30:00.000-07:00

Solaris installation

Step by step guide to Solaris installation:

Solaris installation poses a challenges to the new Solaris sysadmins who have never done the installation of Solaris before . Though the installation itself is simple and straight forward but doing it the first time comes with its own anxiety associated with unexplored and unknown things .
The idea of this article is to introduce you with the procedure and sequence of event Solaris installation to build enough confidence to finish the installation on your own.

1. Before you begin
For Solaris installation on standalone Sun machine you need the following besides sun cpu :

A) Sun Monitor and Sun Keyboard
OR
For carrying the installation through the serial port A of Sun (ttya)
Dumb Terminal or PC with serial port communication software like HyperTerminal
AND
A null modem cable ( Pin 2 & 3 crossed 5 common ground in 9 Pin to 9 pin ; Pin 7 is common ground in 25 Pin connector ) connecting sun's serial port A with PC serial port.

B) You will also require a IP address, netmask and a host name for your system.
2. Getting Started
Installation starts at OK> prompt & you can get to ok> using any of the following method :
1. by pressing Stop A key sequence on a Sun Keyboard.
2. typing #init 0 if your system boots up directly .
3. Pressing ctrl-break or shift-break on a pc keyboard if using pc as
console through serial port.
4. If auto-boot feature is enabled system directly boots up
and gives you a # prompt .You can disable auto-boot so next time it
stays at ok prompt for starting installation.
#/usr/platform/sun4u/bin/eeprom auto-boot?=false
reboot the system.

3. Starting the installation
Insert the installation media - OS CD in CD drive and type boot cdrom at ok> prompt . Ok>boot cdrom
The first phase begins with system identification and gathers information about the system from the the user .System starts booting up and after initialization it asks for language and locale also terminal type in case of PC/terminal
Select your locale and DEC VT100 terminal type for terminal selection
Further installation through the terminal require response to the
selections through ESC and function keys and space bar which are
mentioned on the installation screen.
On the next screens, you are to identify the system as networked or non-networked, and set the default time zone and date/time. After this following host information is required :
A) A host name for the system
B) Whether the system is networked if yes you will have to
provide the IP address & netmask of this machine.

Next you will be asked to select the name services
Name services
[ ] NIS+
[ ] NIS
[ ] DNS
[X ] None
Select the service if you have complete details like domain names etc or select none to configure after installation.
You have to select a distribution type from among the choices choices

4. OS distribution & Disk configuration
After identification is complete the installation process proceeds on to the OS and disk configuration and need your input for these settings. Selection depends on role of your machine
Typical space requirement for Solaris 7 is given here.
[ ] Entire Distribution plus OEM support 64-bit 1242.00 MB (F4 to Customize
[X] Entire Distribution 64-bit .....…...….1215.00 MB
[ ] Developer System Support 64-bit.... 1154.00 MB
[ ] End User System Support 64-bit .….. 765.00 MB
[ ] Core System Support .............. .334.00 MB
Entire distribution with OEM has all software with some third party software
Entire distribution has all software without third party software .
Developer system has run time libraries for C software etc.
End user has X windows and CDE environment .
Core system is without X windows softwares etc.
If you are not sure select entire distribution.
You will be presented with choice to select the boot disk among the disks present in the system ,unless you have reasons select the c0t0d0 at boot disk.
[ X ] c0t0d0 (17269 MB) boot disk 17269 MB
[ ] c0t1d0 (17269 MB) 17269 MB
overlap partition represents entire disk and is slice s2 of the disk.
If any of the disk contain a preexisting partition you will be given a choice to preserve the partition .
Next the current layout is given ( if existing ) and you are asked to select between Automatic and Custom layout of disk partitions.
Automatic layout make a single partition of entire boot disk .
Customize option gives and option to create the partitions and select the sizes . Things to keep in mind while doing interactive or custom installation
Additional space is required in /var & /home if server is to handle mail and printing as mail and print files are formed in /var & if the user home directories are to be located on /home partition
A sample partition table may look like following .
File system/Mount point Disk/Slice Size
---------------------------------------
/ c0t0d0s0 300 MB
swap c0t0d0s1 2000 MB
overlap c0t0d0s2 17269 MB
/usr c0t0d0s3 2000 MB
/opt c0t0d0s4 1000 MB
/var c0t0d0s5 1000 MB
> The swap partition size depends on the size of RAM in the system if you are not sure of its size keep it double the RAM or more than RAM in the system.
> If you are not sure of individual partition sizes of / , /usr /opt & /var make one partition as / and keep its size sufficiently higher than the distribution size you have selected in earlier steps . Always keep in mind the future software that you might have to install like compilers applications etc and log files that will be generated and accumulate in /var directory or partition.
After you have specified the partition sizes it gives summary and error if any
Installation Option: Initial
Boot Device: c0t0d0s0
Client Services: None
Software: Solaris 2.7, Entire Distribution

File System and Disk Layout:
/ c0t0d0s0 300 MB
swap c0t0d0s1 2000 MB
/usr c0t0d0s3 2000 MB
/opt c0t0d0s4 1000 MB
/var c0t0d0s5 1000 MB
one more question is asked about rebooting
[X] Auto Reboot
[ ] Manual Reboot
Afterwards it starts configuring disk making partitions and installing software indicating the progress in a table .
MBytes Installed: 700.66
MBytes Remaining: 0.00
Installing:

0 20 40 60 80 100
After the installation is complete it customizes system files , devices ,logs , installs patches which are there in OS CD for that release. You can install recommended latest patches later
System then reboots or ask you to reboot depending upon the choice selected earlier .
5. After Installation
After rebooting it asks for new root passed and comes to console prompt where you can login as root install patches ,additional softwares , make user etc. etc.

2009-09-21T02:03:00.001-07:00

How to install Ubuntu : The Ubuntu Installation Guide

When it comes to installing Ubuntu, there are so many useful snippets of information on blogs and guides all over the internet. If you Google “How to install Ubuntu”, you’ll see what I mean.
For an Ubuntu beginner or curious Windows intermediate user however, there’s no single, simple source of information when it comes to trying out your first Ubuntu installation. One thing I have noticed is that there’s a lot of technical jargon and sometimes unnecessary terminal commands in lengthy forum posts, but no simple “how to” guides, which I think might put some people off! A shame, when you think about how easy Ubuntu is to install, use and tweak to look really cool!
This post will talk you through your first Ubuntu installation, hopefully teaching you everything you need to know to give Ubuntu a try without breaking or removing your existing Windows installation. The end result will be a “vanilla” Ubuntu Installation running simultaneously with your Windows installation using either the GRUB bootloader, or WUBI, depending on how far you’d like to go on your first Ubuntu experience.

I hope my guide makes installing Ubuntu an enjoyable, simple experience. By the end of the guide you should have a dual boot Windows / Ubuntu machine that happily plays music, video, and acts as a perfectly usable home office computer with Openoffice 3.0. For the really adventurous you could even run Windows XP inside Virtualbox, which is linked to later on in the guide. The Ubuntu OS is unique and seriously cool, so, enjoy the trip.
How to install Ubuntu from a CD:

1) Download the Ubuntu ISO from http://www.ubuntu.com/getubuntu/download and save to your desktop
2) Burn the ISO image to a blank CD using Roxio CD creator or similar:

3) Run the CD from “My Computer” – the CD should ask permission to run at which point you’ll see this option screen:

4) If you’d like to install Ubuntu using Wubi, select “install inside Windows” and follow the instructions. Installing with WUBI is ideal for a first taste of Ubuntu as you can remove from add/remove programs in Windows later on. This install process is really easy but you don’t get the same performance as if Ubuntu had a separate partition running on its EXT3 file system. The following screens are all based on the Wubi installer process, so you can follow the rest of the instructions below.
If you’d like to install Ubuntu separately to Windows, then skip to point 7) below.
Here’s what you see next:

If you’ve got the space on your hard drive, go for 30gb or more for the installation size.
5) Now configure your installation using the simple settings options. You can specify the location of the Ubuntu installation on your Windows partition, the size of the Ubuntu installation, the Ubuntu flavour (Ubuntu, Kubuntu, Xubuntu, etc), your preferred language, and a username and password for the Ubuntu system.
When you click install, you’ll see this screen:

As soon as the files have finished downloading, you’ll see this:

6) That’s it! Click reboot now, and select “Ubuntu” on the startup screen. You now have a fully functional dual boot Windows / Ubuntu machine.
7) Click “Demo and full installation” and your computer will restart and boot into Ubuntu.
Here’s a guide on how to resize or shrink your Windows Vista partition. Follow those instructions before you reboot into the live version of Ubuntu and you’ll have a really easy time during the following steps. Maybe you’d like to install from a USB? Let’s have a quick look at the process of installing from a USB before we continue:

Here’s how to install Ubuntu on a USB drive from Windows Vista:

Format your USB stick with a FAT32 partition from Windows. You can get to the format dialogue by opening My Computer and right mouse clicking the removable drive icon. Click “Format” and follow the settings in the image below. You need a minimum 2gb USB stick.

9) Download UnetBootin. UNetbootin allows for the installation of various Linux/Ubuntu distributions to a partition or USB drive, so it’s no different from a standard install, only it doesn’t need a CD. The coolest thing about the application is that it’s a “portable” app. You don’t need to install it into Windows meaning UNetbootin will run on your Windows PC without “admin” privileges.

The new version of Ubuntu isn’t in the Distribution list supplied with UNetbootin yet, so use the downloaded Ubuntu ISO from earlier on. Add the ISO using the “Diskimage”, make sure your USB drive is selected below and click OK.
The ISO transfers to the USB pretty quickly, so soon after you click OK you’ll see this screen:
10) That’s it – when the installation process is complete, restart your computer and make sure it’s set up to boot from USB. On my HP Laptop, pressing F9 on the boot screen shows a boot order menu. Selecting “USB Hard Drive” follows a black screen, an Ubuntu logo, and finally, your new Ubuntu desktop appears.

Completing your Ubuntu installation, step by step
Installing Ubuntu is so easy that it requires very little effort past this point. If you’ve managed to repartition your hard drive and restart your computer you’ll sail through the next few steps:
11) Click “install” on the live desktop (top left)

12) Choose your language in the welcome screen

13) Choose your location

14) Choose your keyboard layout

15) Set up your disk partition. This is probably the most “technical” part of the installation. When I shrunk my Windows Vista drive volume, I never formatted the new partition, which means the “use the largest continuous free space” option works nicely:

16) Choose your username and password:

17) Migrate your Windows documents and settings

18) You’re now ready to install your new Ubuntu installation

19) When the installation has finished, restart your computer (you’ll be instructed to remove your cd rom or USB drive). You’re now ready to begin using Ubuntu!

2009-09-18T01:17:00.000-07:00

Install Windows XPInstallation process
Installing Windows XP can take up to two hours. To make the process more manageable, it has been broken up into several sections. When you are ready, install Windows XP:
•Part 1: Begin the installation
•Part 2: Continue the installation
•Part 3: Complete the installation
Part 1: Begin the installation
1.Insert the Windows XP CD into your computer and restart your computer.
2.If prompted to start from the CD, press SPACEBAR. If you miss the prompt (it only appears for a few seconds), restart your computer to try again.

3.Windows XP Setup begins. During this portion of setup, your mouse will not work, so you must use the keyboard. On the Welcome to Setup page, press ENTER.

4.On the Windows XP Licensing Agreement page, read the licensing agreement. Press the PAGE DOWN key to scroll to the bottom of the agreement. Then press F8.

5.This page enables you to select the hard disk drive on which Windows XP will be installed. Once you complete this step, all data on your hard disk drive will be removed and cannot be recovered. It is extremely important that you have a recent backup copy of your files before continuing. When you have a backup copy, press D, and then press L when prompted. This deletes your existing data.
6.Press ENTER to select Unpartitioned space, which appears by default.

7.Press ENTER again to select Format the partition using the NTFS file system, which appears by default.

8.Windows XP erases your hard disk drive using a process called formatting and then copies the setup files. You can leave your computer and return in 20 to 30 minutes.

Part 2: Continue the installation

9.Windows XP restarts and then continues with the installation process. From this point forward, you can use your mouse. Eventually, the Regional and Language Options page appears. Click Next to accept the default settings. If you are multilingual or prefer a language other than English, you can change language settings after setup is complete.

10.On the Personalize Your Software page, type your name and your organization name. Some programs use this information to automatically fill in your name when required. Then, click Next.
11.On the Your Product Key page, type your product key as it appears on your Windows XP CD case. The product key is unique for every Windows XP installation. Then, click Next.
12.On the Computer Name and Administrator Password page, in the Computer name box, type a name that uniquely identifies your computer in your house, such as FAMILYROOM or TOMS. You cannot use spaces or punctuation. If you connect your computer to a network, you will use this computer name to find shared files and printers. Type a strong password that you can remember in the Administrator password box, and then retype it in the Confirm password box. Write the password down and store it in a secure place. Click Next.
13.On the Date and Time Settings page, set your computer’s clock. Then, click the Time Zone down arrow, and select your time zone. Click Next.

14.Windows XP will spend about a minute configuring your computer. On the Networking Settings page, click Next.
15.On the Workgroup or Computer Domain page, click Next.

Part 3: Complete the installation

16.Windows XP will spend 20 or 30 minutes configuring your computer and will automatically restart when finished. When the Display Settings dialog appears, click OK.
17.When the Monitor Settings dialog box appears, click OK.

18.The final stage of setup begins. On the Welcome to Microsoft Windows page, click Next.
19.On the Help protect your PC page, click Help protect my PC by turning on Automatic Updates now. Then, click Next.

20.Windows XP will then check if you are connected to the Internet:
•If you are connected to the Internet, select the choice that describes your network connection on the Will this computer connect to the Internet directly, or through a network? page. If you’re not sure, accept the default selection, and click Next.

If you use dial-up Internet access, or if Windows XP cannot connect to the Internet, you can connect to the Internet after setup is complete. On the How will this computer connect to the Internet? page, click Skip.

21.Windows XP Setup displays the Ready to activate Windows? page. If you are connected to the Internet, click Yes, and then click Next. If you are not yet connected to the Internet, click No, click Next, and then skip to step 24. After setup is complete, Windows XP will automatically remind you to activate and register your copy of Windows XP.

22.On the Ready to register with Microsoft? page, click Yes, and then click Next.

23.On the Collecting Registration Information page, complete the form. Then, click Next.

24.On the Who will use this computer? page, type the name of each person who will use the computer. You can use first names only, nicknames, or full names. Then click Next. To add users after setup is complete or to specify a password to keep your account private, read Create and customize user accounts.

25.On the Thank you! page, click Finish.

Congratulations! Windows XP setup is complete. You can log on by clicking your name on the logon screen. If you’ve installed Windows XP on a new computer or new hard disk drive, you can now use the File and Settings Transfer Wizard to copy your important data to your computer or hard disk drive.
After logon, take a few minutes to validate your copy of Windows. Validation gives you access to hundreds of free downloads from the Microsoft Download Center. To learn about the new features Windows XP provides, click the Start button, click All Programs, click Accessories, and then click Tour Windows XP.

2009-09-17T02:57:00.000-07:00

Installing Windows 2000 Professional

To install Windows 2000 Professional, follow these steps:

1.Start the installation by using one of the following methods:

Start from the Windows 2000 Professional installation CD-ROM. Make sure that the CD-ROM is set to start before the hard disk starts. Insert the CD-ROM, and then when you are prompted, press any key to start the Windows 2000 Professional Setup program.
Start from boot disks. Insert Disk 1, and then insert each of the remaining three floppy disks when you are prompted to do so. For additional information about creating boot disks for Windows 2000, click the article number below to view the article in the Microsoft Knowledge Base:
197063 (http://support.microsoft.com/kb/197063/EN-US/ ) How to Create Setup Boot Disks for Windows 2000
Start from within a current operating system. Insert the CD-ROM, and then, at a command prompt, type drive:\i386\winnt32.exe and then press ENTER, or if this is an installation on a computer that has no previous installation of Windows, type drive:\i386\winnt.exe and then press ENTER, where drive is the letter of the CD-ROM drive.

2.Setup inspects your computer's hardware configuration and then begins to install the Setup and driver files. When the Microsoft Windows 2000 Professional screen appears, press ENTER to set up Windows 2000 Professional.

3.Read the license agreement, and then press the F8 key to accept the terms of the license agreement and continue the installation.

4.When the Windows 2000 Professional Setup screen appears, either press ENTER to set up Windows 2000 Professional on the selected partition, or press C to create a partition in the unpartitioned space.

5.If you choose to install Windows 2000 Professional on a file allocation table (FAT) partition, specify whether you want to:

Leave the current file system intact.
Format the partition as FAT16.
Convert the existing file system to the NTFS file system.
Format the partition by using the NTFS file system.

Press ENTER after you make your selection. Setup examines the existing hard disks and then copies the files that are needed to complete the installation of Windows 2000 Professional. After the files are copied, the computer restarts.

Important Do not press a key to boot from your CD-ROM drive when your computer restarts.

6.When the Windows 2000 GUI Mode Setup Wizard appears, click Next to start the wizard. Setup detects and installs such devices as a specialized mouse or keyboard.

7.When the Regional Options dialog box appears, customize your installation of Windows 2000 Professional for locale, number format, currency, time, date, and language, if necessary. Click Next.

8.In the Personalize Your Software dialog box, type your name and the name of your organization, and then click Next.

9.In the Product ID dialog box, type the 25-character product key, and then click Next.

10.In the Computer Name and Password dialog box, either accept the default name that Setup generates or assign a different name for the computer. When you are prompted for an administrative password, type a password for the Administrator account. (You can leave the box blank; however, this is not recommended.) Click Next.

11.In the Date and Time Settings dialog box, set the correct date and time for your computer. You can also specify which time zone you are in and set the computer to automatically adjust the clock for daylight saving time. Click Next.

12.Setup installs the networking software and detects your network settings. When the Network Settings dialog box appears, click either

Typical to set default network settings such as File and Print Sharing for Microsoft Networks, Client for Microsoft Networks, and TCP/IP protocol that uses Dynamic Host Configuration Protocol (DHCP), or
Custom to specify the network components that you require for your network environment,

and then click Next.

13.In the Workgroup or Computer Domain dialog box, specify the workgroup or the domain to join. If you indicate that you are part of a domain, specify your domain user name and password. Click Next.

Setup installs the networking components.

14.During the final stage of installation, Setup installs Start menu items, registers components, saves settings, and removes temporary files. When the Completing the Windows 2000 Setup Wizard dialog box prompts you to do so, remove the Windows 2000 CD-ROM, and then click Finish to restart the computer.

15.After the computer restarts, click Next in the Welcome to the Network Identification Wizard dialog box.

16.In the Users of This Computer dialog box, specify either that users must enter a user name and password or that you want Windows 2000 to automatically log on a specific user when the computer starts. Click Finish.

When the Windows 2000 Professional desktop appears, the installation is complete.

2009-08-27T02:33:00.000-07:00

Resource-Allocation Graph

A set of vertices V and a set of edges E.

V is partitioned into two types:
=>FP = {P1, P2, …, Pn}, the set consisting of all the processes in the system.
=>FR = {R1, R2, …, Rm}, the set consisting of all resource types in the system.
request edge – directed edge P1 ® Rj.
assignment edge – directed edge Rj ® Pi

Resource-Allocation Graph Algorithm

Claim edge Pi ® Rj indicated that process Pj may request resource Rj; represented by a dashed line.
Claim edge converts to request edge when a process requests a resource.
When a resource is released by a process, assignment edge reconverts to a claim edge.
Resources must be claimed a priori in the system.

Resource-Allocation Graph and Wait-for Graph

Resource-Allocation Graph Corresponding wait-for graph

How did you know if there is a deadlock based on a resource allocation graph?

In a multiprogramming system, processes request resourceused by other processes then the process enters a processes are also in a waiting state, we have deadlock.

2009-08-27T01:42:00.000-07:00

Example of a Resource Allocation Graph

Resource allocation graphs are drawn in order to see the allocatioand resources easily. In these graphs, processes are represented are represented by boxes. Resource boxes have some number available number of that resource, that is number of instances.

• If the resource allocation graph contains no cycles then there is no deadlock in the system at that instance.
• If the resource allocation graph contains a cycle then a deadlock may exist.
• If there is a cycle, and the cycle involves only resources which have a single instance, then a deadlock has occurred.

Resource Allocation Graph With A Deadlock

*In addition to the request and assignment edges, a claim edge is also introduced.
*Claim edge Pi ® Rj indicated that process Pj may request resource Rj in future; represented by a dashed line.
*Claim edge converts to request edge when a process requests a resource.
*When a resource is released by a process, assignment edge reconverts to a claim edge.
*Resources must be claimed a priori in the system. That is, before a process starts executing, all of its claim edges must already appear in the resource-allocation graph.
*Suppose that process Pi requests resource Rj. The request can be granted only if converting the request edge if converting the request edge Pi®Rj to an assignment edge does not result in a cycle in the resource-allocation graph. That is we use a cycle detection algorithm is used. If no cycle exits, the process Pi will have to wait.

Resource Allocation Graph With A Cycle But No Deadlock

*2 resources "R1, R2"
*4 processes "P1, P2, P3, P4"
*P1 and P3 is requesting a process to R1 and R2 respectively.
*P2 and P3 holds an instance of R1
*P1 and P4 holds an instance of R2
*There is no DeadLock

Resource-Allocation Graph For Deadlock Avoidance

The Resource Allocation Graph (RAG) is composed of 2 processes and 2 resources.
· P1 holds an instance of R1
· P2 requests an instance of R1
· P1 and P2 may request an instance of R2

Unsafe State In Resource-Allocation Graph

*the graph shows that R1 is holding the instances of P1, then P1 is requesting for a resource in R2, then R2 is holding the instances of P2 and P2 is requesting instance of R1.

2009-08-20T04:15:00.000-07:00

Methods for Handling

Deadlock

• Prevent
– write code such that the necessary conditions can
never hold simultaneously
• Avoid
– dynamically ensure that a deadlock state is not
reachable.
• Detect and recover
– allow deadlock but provide mechanisms to detect
it and recover (e.g., kill a process)
• Ignore (ostrich approach)
pretend they cannot occur and reboot if they do.

2009-08-20T04:13:00.000-07:00

Deadlock Prevention

Disallow one of the four necessary conditions for deadlock
Preventing deadlocks by constraining how requests for resources can be made in the system and how they are handled (system design).
The goal is to ensure that at least one of the necessary conditions for deadlock can never hold.

2009-08-20T04:10:00.000-07:00

Deadlock Detection

Always grant resource request when possible. Periodically check for deadlocks. If a deadlock exists, recover from it.

2009-08-20T04:05:00.000-07:00

Deadlock Recovery

Abort all deadlock processes and release resource - too drastic - will lead to loss of work.
Abort one process at a time - releasing resources until no deadlockHow do we determine which process to abort first ? - priority ordering, process which has done least work.
Selectively restart processes from a previous checkpoint i.e. before it claimed any resources difficult to achieve - sometimes impossible.
Successively withdraw resources from a process and give to another process until deadlock is broken. How to choose which processes and which resources ?

Complex decisions due to the large number of processes present within a system.
Difficult to automate.
Use Operator to resolve conflicts - BUT this requires the operator to have skill and understanding of what processes are actually doing.

2009-08-20T03:59:00.000-07:00

Deadlock Characterization

Necessary conditions:

1) Mutual exclusion:
• at least one shared resource is held
2) Hold and wait:
• a process must be holding at least one resource and
waiting for another
3) No preemption:
• cannot steal a resource away from a process
4) Circular wait:
• E.g., A is waiting for B who is waiting for C who is
waiting for A.

2009-08-13T04:16:00.000-07:00

Real Time Scheduling

• Correctness of the system may depend not only on the logical result of the computation but also on the time when these results are produced, e.g.

–> Tasks attempt to control events or to react to events that take place in the outside world
–> These external events occur in real time and processing must be able to keep up
–> Processing must happen in a timely fashion,• neither too late, nor too early

Thread Scheduling

->Distinction between user-level and kernel-level threads
OS only schedules kernel-level threads. User-level threads are scheduled through a direct or indirect (LWP) mapping
->Many-to-one and many-to-many models, thread library schedules user-level threads to run on LWP
->Known as process-contention scope (PCS) since scheduling competition is within the process
->Kernel thread scheduled onto available CPU is system-contention scope (SCS) – competition among all threads in system
->Typically – PCS is priority based. Programmer can set user-level thread priorities

thread scheduling criteria:

-> a priority, or in fact usually multiple "priority" settings that we'll discuss below;
-> a quantum, or number of allocated timeslices of CPU, which essentially determines the amount of CPU time a thread is allotted before it is forced to yield the CPU to another thread of the same or lower priority
-> a state, notably "runnable" vs "waiting";
-> metrics about the behaviour of threads, such as recent CPU usage or the time since it last ran (i.e. had a share of CPU), or the fact that it has "just received an event it was waiting for".

Multiprocessor Scheduling

-> is an NP-Complete optimization problem.
-> Given a set of runnable threads, and a set of CPUs, assign threads to CPUs
-> Same considerations as uniprocessorscheduling
(Fairness, efficiency, throughput, response time…)
-> But also new considerations:
* Load balancing
* Processor affinity
-> Will consider only shared memory multiprocessor
Central queue – queue can be a bottleneck
Distributed queue – load balancing between queue

2009-08-10T19:32:00.000-07:00

CPU Scheduling Algorithms

Scheduling Algorithms
1.First-come, first-served (FCFS) scheduling
2.Shortest-job first (SJF) scheduling
3.Priority scheduling
4.Round-robin scheduling
5.Multilevel queue scheduling
6.Multilevel feedback queue scheduling

-> First-come, First-served (FCFS) scheduling is the simplest scheduling algorithm, but it can cause short processes to wait for very long processes.
-> Shortest-job-first (SJF) scheduling is provably optimal, providing the shortest average waiting time. Implementing SJF scheduling is difficult because predicting the length of the next CPU burst is difficult. The SJF algorithm is a special case of the general priority-scheduling algorithm, which simply allocates the CPU to the highest-priority process. Both priority and SJF scheduling may suffer from starvation. Aging is a technique to prevent starvation.
->Priority Based Scheduling Run highest-priority processes first, use round-robin among processes of equal priority. Re-insert process in run queue behind all processes of greater or equal priority.Allows CPU to be given preferentially to important processes.Scheduler adjusts dispatcher priorities to achieve the desired overall priorities for the processes, e.g. one process gets 90% of the CPU.Comments: In priority scheduling, processes are allocated to the CPU on the basis of an externally assigned priority. The key to the performance of priority scheduling is in choosing priorities for the processes.
-> Round-robin (RR) scheduling is more appropriate for a time-shared (interactive) system. RR scheduling allocates the CPU to the first process in the ready queue for q time units, where q is the time quantum. After q time units, if the process has not relinquished the CPU, it is preempted and the process is put at the tail of the ready queue. The major problem is the selection of the time quantum. If the quantum is too large, RR scheduling degenerates to FCFS scheduling; if the quantum is too small, scheduling overhead in the form of context-switch time becomes excessive.The FCFS algorithm is nonpreemptive, the RR algorithm is preemptive. The SJF and priority algorithms may be either preemptive or nonpreemptive.
-> Multilevel queue algorithms allow different algorithms to be used for various classes of processes. The most common is a foreground interactive queue which uses RR scheduling, and a background batch queue, which uses FCFS scheduling. Multilevel feedback queues allow processes to move from one queue to another.

Because such a wide variety of scheduling algorithms are available, we need methods to select among them. Analytic methods use mathematical analysis to determine the performance of an algorithm. Simulation methods determine performance by imitating the scheduling algorithm on a “representative” sample of processes, and computing the resulting performance.

Operating Systems supporting threads at the kernel level must schedule threads - not processes - for execution. This is the case with Solaris 2 and Windows 2000 where both systems schedule threads using preemptive priority based on scheduling algorithm including support for real-time threads. The Linux process scheduler also uses a priority-based algorithm with real-time supports as well. The scheduling algorithms for these three operating systems typically favor interactive over batch and CPU-bound processes.systems typically favor interactive over batch and CPU-bound processes.

2009-08-10T19:10:00.000-07:00

Substantial Information about Threads of atleast three OS

WINDOWS XP THREAD

Implements the one-to-one mapping
Each thread contains
-> A thread id
-> Register set
-> Separate user and kernel stacks
-> Private data storage area
The register set, stacks, and private storage area are known as the context of the threads
The primary data structures of a thread include:
-> ETHREAD (executive thread block)
-> KTHREAD (kernel thread block)
-> TEB (thread environment block)

JAVA THREADS

-> Java threads are managed by the JVM
-> Java threads may be created by:

Extending Thread class
Implementing the Runnable interface

Windows 2000

Implements the one-to-one mapping

Each thread contains

->A thread ID

->Register set

->Separate user and kernel stacks for user and kernel modes

->Private data storage area used by various run-time libraries and dynamic link libraries (DDLs)

->The latter three are known as the context of the thread and are architecture-specific to HW.

2009-08-05T03:52:00.000-07:00

Procedure-Consumer Example

PROCEDURE

A Procedure encapsulates a task composed of Steps (and possibly, SubSteps). Procedures are usually performed sequentially, unless individual Steps direct the reader explicitly.Often it is important to assure that certain conditions exist before a procedure is performed, and that the outcome of the procedure matches the expected results. DocBook does not provide explicit semantic markup for these pre- and post-conditions. Instead, they must be described as steps (check the pre-conditions in the first step and the results in the last step), or described outside the body of the procedure.

CONSUMER

Consumer is a broad label that refers to any individuals or households that use goods and services generated within the economy. The concept of a consumer is used in different contexts, so that the usage and significance of the term may vary.

2009-08-05T03:50:00.000-07:00

Thread Library

The threads library allows concurrent programming in Objective Caml. It provides multiple threads of control (also called lightweight processes) that execute concurrently in the same memory space. Threads communicate by in-place modification of shared data structures, or by sending and receiving data on communication channels.The threads library is implemented by time-sharing on a single processor. It will not take advantage of multi-processor machines. Using this library will therefore never make programs run faster. However, many programs are easier to write when structured as several communicating processes.

2009-08-05T03:39:00.000-07:00

Kernel threads

=> Supported by the Kernel
=> Kernel can run them on multiple processors in parallel

2009-08-05T03:38:00.000-07:00

User thread

=> Thread management done by user-level threads library
=> includes a set of registers and a stack, and shares the entire address space with the other threads in the enclosing process
=> is handled entirely in user code, usually by a special library that provides at least start, swap and suspend calls

2009-08-05T03:28:00.001-07:00

Thread

In computer science, a thread of execution results from a fork of a computer program into two or more concurrently running tasks. The implementation of threads and processes differs from one operating systemto another, but in most cases, a thread is contained inside a process. Multiple threads can exist within the same process and share resources such as memorywhile different processes do not share these resources.

2009-08-05T03:12:00.001-07:00

Multithreading models

•There are three dominant models for thread libraries, each with its own trade-offs
–many threads on one LWP (many-to-one)
–one thread per LWP (one-to-one)
–many threads on many LWPs (many-to-many)
•Similar models can apply on scheduling kernel threads to real CPUs
Many-to-one
=> Many user-level threads mapped to single kernel thread

•In this model, the library maps all threads to a single lightweight process•Advantages:

–totally portable
–easy to do with few systems dependencies

•Disadvantages:

–cannot take advantage of parallelism

–may have to block for synchronous I/O

–there is a clever technique for avoiding it

•Mainly used in language systems, portable libraries
One-to-one

=>Many user-level threads mapped to single kernel thread

•In this model, the library maps each thread to a different lightweight process

•Advantages:

–can exploit parallelism, blocking system calls

•Disadvantages:–thread creation involves LWP creation

–each thread takes up kernel resources

–limiting the number of total threads

•Used in LinuxThreads and other systems where LWP creation is not too expensive

Many-to-many => Allows many user level threads to be mapped to many kernel threads
=> Allows the operating system to create a sufficient number of kernel threads

•In this model, the library has two kinds of threads: bound and unbound

–bound threads are mapped each to a single lightweight process

–unbound threads may be mapped to the same LWP

•Probably the best of both worlds

•Used in the Solaris implementation of Pthreads (and several other Unix implementations)

2009-08-05T03:02:00.001-07:00

Benefits of Multi-Threaded Programming Multi-threading as a widespread programming and execution model allows multiple threads to exist within the context of a single process. These threads share the process' resources but are able to execute independently. The threaded programming model provides developers with a useful abstraction of concurrent execution. However, perhaps the most interesting application of the technology is when it is applied to a single process to enable parallel execution on a multiprocessor system.

This advantage of a multithreaded program allows it to operate faster on computer systems that have multiple CPUs, CPUs with multiple cores, or across a cluster of machines — because the threads of the program naturally lend themselves to truly concurrent execution. In such a case, the programmer needs to be careful to avoid race conditions, and other non-intuitive behaviors. In order for data to be correctly manipulated, threads will often need to rendezvous in time in order to process the data in the correct order. Threads may also require atomic operations (often implemented using semaphores) in order to prevent common data from being simultaneously modified, or read while in the process of being modified. Careless use of such primitives can lead to deadlocks.

Another advantage of multithreading, even for single-CPU systems, is the ability for an application to remain responsive to input. In a single threaded program, if the main execution thread blocks on a long running task, the entire application can appear to freeze. By moving such long running tasks to a worker thread that runs concurrently with the main execution thread, it is possible for the application to remain responsive to user input while executing tasks in the background.

Operating systems schedule threads in one of two ways:

1. Preemptive multithreading is generally considered the superior approach, as it allows the operating system to determine when a context switch should occur. The disadvantage to preemptive multithreading is that the system may make a context switch at an inappropriate time, causing priority inversion or other negative effects which may be avoided by cooperative multithreading.

2. Cooperative multithreading, on the other hand, relies on the threads themselves to relinquish control once they are at a stopping point. This can create problems if a thread is waiting for a resource to become available.

Traditional mainstream computing hardware did not have much support for multithreading as switching between threads was generally already quicker than full process context switches. Processors in embedded systems, which have higher requirements for real-time behaviors, might support multithreading by decreasing the thread-switch time, perhaps by allocating a dedicated register file for each thread instead of saving/restoring a common register file. In the late 1990s, the idea of executing instructions from multiple threads simultaneously has become known as simultaneous multithreading. This feature was introduced in Intel's Pentium 4 processor, with the name hyper threading.

2009-07-30T02:03:00.000-07:00

INTERPROCESS COMMUNICATION

Direct Communication

Direct communication can be defined as speech that specifically states and directs an action. Most of us grew up hearing direct speech from our parents or teachers: "Get that homework done before you go out to play," or, from our boss today we might hear: "I need this on my desk by Friday."

When to Use Direct Communication:
Direct communication is often necessary in working environments. There are plenty of situations when a direct style is the only appropriate option. The following situations call for this form of speech.

Indirect Communication

Unlike direct communication, a indirect style of speech is not typically authoritative, rather it encourages input from the listener. By using this method, you give the other person the opportunity to speak up. An indirect style, makes them feel as if their ideas are important. This style of communication places the listener in the "one-up" position.

When to Use Indirect Communication:
Like direct communication, indirect communication can be very useful in the workplace. This method can make teams run more smoothly and create an environment of friendly respect.

Synchronization

refers to one of two distinct but related concepts: synchronization of processes, and synchronization of data. Process synchronization refers to the idea that multiple processes are to join up or handshake at a certain point, so as to reach an agreement or commit to a certain sequence of action. Data synchronization refers to the idea of keeping multiple copies of a dataset in coherence with one another, or to maintain data integrity. Process synchronization primitives are commonly used to implement data synchronization.

=>processes takes place by calls to send and receive primitives

Blocking send

A blocking send returns as soon as the send buffer is free for reuse, that is, as soon as the last byte of data has been sent or placed in an internal buffer.

Nonblocking send

A non-blocking send returns as soon as possible, that is, as soon as it has posted the send. The buffer might not be free for reuse.

Blocking receive

A blocking receive returns as soon as the data is ready in the receive buffer.

Nonblocking receive

A non-blocking receive returns as soon as possible, that is, either with a flag that the data has not arrived yet or with the data in the receive buffer.

Buffering

=>Buffering Messages reside in a temporary queue Zero capacity Bounded capacity Unbounded capacity.

Link may have some capacity that determines the number of message that can be temporarily queued in it .

Zero Capacity

Explicit buffering – Zero-capacity (blocking sender, receiver)

Zero capacity: (queue of length 0)

No messages wait.
Sender must wait until receiver receives the message — this synchronization to exchange data is called a rendezvous.

Bounded Capacity

– Bounded capacity: when queue is not full, message is copied into buffer (or a pointer is kept).

Bounded capacity: (queue of length)

If receiver’s queue is not full, new message is put on queue,and sender can continue executing immediately.
If queue is full, sender must block until space is available in the queue.

Unbounded Capacity

Unbounded capacity: (infinite queue)

Sender can always continue

Producer-Consumer Example

Procedure

A producer which generates data items and puts them in a buffer e.g. from a file

Consumer

A consumer which removes items from the buffer e.g. to a printer.

2009-07-16T03:36:00.000-07:00

Interprocess Communication

For communication and synchronization
–Shared memory
–OS provided IPC
Message system
–no need for shared variable
– two operations
•send(message) – message size fixed or variable
•receive(message)
If P and Q wish to communicate, they need to
–establish a communication link between them
–exchange messages via send/receive
Implementation of communication link
–physical (e.g., shared memory, hardware bus)
–logical (e.g., logical properties)

2009-07-16T03:20:00.000-07:00

Cooperating Process

Advantages of process cooperation
–Information sharing
–Computation speed-up
–Modularity
–Convenience
Independent process cannot affect/be affected by the execution of another process, cooperating ones can
Issues
–Communication
–Avoid processes getting into each other’s way
–Ensure proper sequencing when there are dependencies
Common paradigm: producer-consumer
–unbounded-buffer - no practical limit on the size of the buffer
–bounded-buffer - assumes fixed buffer size

2009-07-16T02:33:00.000-07:00

The Concept of Process

a. Process State

In a multitasking computer system, processes may occupy a variety of states. These distinct states may not actually be recognized as such by the operating system kernel, however they are a useful abstraction for the understanding of processes.

Primary Process States

The following typical process states are possible on computer systems of all kinds. In most of these states, processes are "stored" on main memory.

b. Process Control Block

A Process Control Block (PCB, also called Task Control Block or Task Struct) is a data structure in the operating system kernel containing the information needed to manage a particular process. The PCB is "the manifestation of a process in an operating system".

Included information:

Implementations differ, but in general a PCB will include, directly or indirectly:
The identifier of the process (a process identifier, or PID)
Register values for the process including, notably,
the Program Counter value for the process
The address space for the process
Priority (in which higher priority process gets first preference. eg., nice value on Unix operating systems)
Process accounting information, such as when the process was last run, how much CPU time it has accumulated, etc.
Pointer to the next PCB i.e. pointer to the PCB of the next process to run

I/O Information (i.e. I/O devices allocated to this process, list of opened files, etc)

During a context switch, the running process is stopped and another process is given a chance to run. The kernel must stop the execution of the running process, copy out the values in hardware registers to its PCB, and update the hardware registers with the values from the PCB of the new process.
c. Threads

A thread of execution results from a fork of a computer program into two or more concurrently running tasks. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process. Multiple threads can exist within the same process and share resources such as memory, while different processes do not share these resources.

On a single processor, multithreading generally occurs by time-division multiplexing (as in multitasking): the processor switches between different threads. This context switching generally happens frequently enough that the user perceives the threads or tasks as running at the same time. On a multiprocessor or multi-core system, the threads or tasks will generally run at the same time, with each processor or core running a particular thread or task. Support for threads in programming languages varies: a number of languages simply do not support having more than one execution context inside the same program executing at the same time.

2009-07-16T02:03:00.000-07:00

Processing Scheduling

a. Scheduling Queues
Job queue – set of all processes in the system.
Ready queue – set of all processes residing in main memory,
ready and waiting to execute.
Device queues – set of processes waiting for an I/O device.
Process migration between the various queues.
b.Schedulers
Scheduler is a tool that is intented to help understand how real-time algorithms work.
As of release 10.0, HP-UX implements four schedulers, two time-share and two real-time.
To choose a scheduler, you can use the user command, rtsched(1), which executes processes with your choice of scheduler and enables you to change the real-time priority of currently executing process ID.
rtsched -s scheduler -p priority command [arguments] rtsched [ -s scheduler ] -p priority -P pid
Likewise, the system call rtsched(2) provides programmatic access to POSIX real-time scheduling operations.
c. Context Switch
A context switch is the computing process of storing and restoring the state (context) of a CPU such that multiple processes can share a single CPU resource. The context switch is an essential feature of a multitasking operating system. Context switches are usually computationally intensive and much of the design of operating systems is to optimize the use of context switches. A context switch can mean a register context switch, a task context switch, a thread context switch, or a process context switch. What constitutes the context is determined by the processor and the operating system.

2009-07-16T01:46:00.000-07:00

Operation on Process

a. Process Creation

Process 0 is created and initialized at system boot time but all other processes are created by a fork() or vfork() system call.

The fork() system call causes the creation of a new process. The new (child) process is an exact copy of the calling (parent) process.
vfork() differs from fork() only in that the child process can share code and data with the calling process (parent process). This speeds cloning activity significantly at a risk to the integrity of the parent process if vfork() is misused.

b. Process Termination

Processes terminate in one of two ways:

Normal Termination occurs by a return from main or when requested by an explicit call to exit or _exit.
Abnormal Termination occurs as the default action of a signal or when requested by abort.

When a process finishes executing, HP-UX terminates it using the exit system call.
Circumstances might require a process to synchronize its execution with a child process. This is done with the wait system call, which has several related routines.
During the exit system call, a process enters the zombie state and must dispose of child processes. Releasing process and thread structures no longer needed by the exiting process or thread is handled by three routines -- freeproc(), freethread(), and kissofdeath().

Quiz #3

2009-07-09T03:58:00.000-07:00

1.What are the major activities of the OS with regards to process management?

=>Process creation and deletion

=>Process suspenion and resumption

=>Provision of mechanisms for:

* process synchronization
*process communication
*deadlock handling

2.What are the major activities of the OS with regards to main-memory management?

=>Keep track which parts of memory are currently being used and by whom.

=>Decide which processes to load when memory space becomes available.

=>Allocate and deallocate memory space as needed.

3.What are the major activities of the OS with regards to secondary-storage management?

=>Free space management

=>Storage allocation

=>Disk scheduling

4.What are the major activities of the OS with regards to file management?

=>File creation and deletion

=>Directory creation and deletion

=>Support of primitives for manipulating files and directories

=>File backup on stable (nonvolatile) storage media

=>Mapping files onto secondary storage

5.What is the purposeof the command interpreter?

=> It reads commands from the user or from a ﬁle of commandsand executes them, usually by turning them into one or more systemcalls. It is usually not part of the kernel since the command interpreteris subject to changes.

2009-07-07T04:15:00.000-07:00

SYSTEM BOOT

Set The System's Boot Device Sequence

AMI-BIOS: For most versions, managing a PC's boot device sequence appears under the "Advanced BIOS Features" menu
If your PC has a relatively new motherboard, its BIOS will already include the functions necessary to support USB-attached boot media. If so, you need only make the right selections in that BIOS menu to boot from a USB flash drive. Older PCs, on the other hand, won't accept USB drives as valid boot devices. This means a BIOS update that supports USB boot options is necessary. You can find information about where to obtain such updates from your PC's (or motherboard's) user manual, on the driver CD included with the PC (or motherboard) or on the vendor's Website.
Normally, the hard disk precedes the USB flash drive (which falls under the heading of USB-HDD in most BIOS menus) in the boot order. If the hard disk contains a viable boot sector, the PC will start up automatically using the information it contains. Only when the hard disk suffers from a boot sector defect or an operating system can't be found will the PC boot from the USB flash drive instead.
Change this boot order. Plug the flash drive in, boot the computer and enter the BIOS setup utility. Normally, this means holding down the DEL or F2 key just as the computer powers up and begins the boot process. If you read the initial startup screen on your PC carefully, it will tell you exactly what you must do to access and alter your BIOS settings.
If your PC uses AMI-BIOS from American Megatrends, there are two possible ways to alter the boot device sequence. Each varies depending on the version of AMI-BIOS that's installed.
For the first variant, there is no menu entry named "Boot." Navigate to the sub-menu named "Advanced BIOS Features." Navigate to the item named "Boot Device Select... " and designate the USB flash drive as the first device in the "Boot Device Priority" list by selecting "1st" as its value. Then, hit the Esc key and set both the "Quick Boot" and "Full Screen LOGO Show" items to "Disabled" (this lets you see the BIOS messages during startup on the monitor). Exit the BIOS Setup utility using the "Save and Exit Setup" item in the main menu.
For the second variant, use the "Boot" menu to select the USB flash drive. It will show up under one of the following headings: "Hard Disk Drive", "Removable Device" or "Removable Storage Device. " Next, select the USB flash drive as "1st Drive" in the first position, then hit the Esc key. That device should appear in the menu named "Boot Device Priority" which might also show up as "Boot Sequence". Inside that menu, designate the USB flash drive as the "1st Boot Device", hit the Esc key and save all changes in the "Exit" menu by selecting "Exit and Save Changes".
The Phoenix BIOS that's so popular in notebook computers also lists the USB flash drive in its "Boot" menu (which might also appear as "Boot Device Priority"). In this case, the flash drive may show up as an entry in the "-HDD" or "-Removable Devices" sub-menu. Select the device class ("-Hard Drive" or "-HDD" for example) and use the F6 key to move the flash drive to the top of that list. Exit the BIOS Setup program by striking the F10 key, followed by the Enter key, to save all settings.

2009-07-07T03:33:00.000-07:00

SYSTEM GENERATION

An operational system is a combination of the z/TPF system, application programs, and people. People assign purpose to the system and use the system. The making of an operational system depends on three interrelated concepts:
*System definition: The necessary application and z/TPF system knowledge required to select the hardware configuration and related values used by thez/TPF system software.
*System initialization: The process of creating the z/TPF system tables and configuration-dependent system software.
*System restart and switchover: The procedures used by the z/TPF system software to ready the configuration for online use.

The first two items are sometimes collectively called system generation; also installing and implementing. System definition is sometimes called design. System restart is the component that uses the results of a system generation to place the system in a condition to process real-time input. The initial startup is a special case of restart and for this reason system restart is sometimes called initial program load, or IPL. System restart uses values found in tables set up during system generation and changed during the online execution of the system. A switchover implies shifting the processing load to a different central processing complex (CPC), and requires some additional procedures on the part of a system operator. A restart or switchover may be necessary either for a detected hardware failure, detected software failure, or operator option. In any event, system definition (design), initialization, restart, and switchover are related to error recovery. This provides the necessary background to use this information, which is the principal reference to be used to install the z/TPF system.

Performing a system generation requires a knowledge of the z/TPF system structure, system tables, and system conventions, a knowledge of the applications that will be programmed to run under the system, and a user's knowledge of z/OS. Knowledge of the z/TPF system, Linux, and the application are required to make intelligent decisions to accomplish the system definition of a unique z/TPF system environment. The use of z/OS and Linux is necessary because many programs used to perform system generation run under control of z/OS or Linux. Although this information does not rely on much z/OS or Linux knowledge, when the moment arrives to use the implementation information, the necessary z/OS and Linux knowledge must be acquired. You are assumed to have some knowledge of the S/370 assembly program as well as jargon associated with the z/OS and Linux operating systems. Some knowledge of C language is also helpful, because some of the programs that are used to generate the system are written in C.

2009-07-07T02:55:00.000-07:00

VIRTUAL MACHINE

Implementation

Virtual machines are usually written in “portable” (in the sense that compilers for most architectures already exists) programming languages such as C or C++.
For performance critical components assembly language can be used.
Some VMs (Lisp, Forth, Smalltalk) are largely written in the language itself.
Many VMs are written specifically for gcc, for reasons that will become clear in later slides.

Benefits

Partitioning – Multiple
application and OS
instances in a single
machine
Isolation – Each virtual
machine is isolated from
the host and other virtual
machines
Encapsulation – Each
entire virtual machine state
is contained in software;
standard virtual hardware
guarantees compatibility.

Examples

Examples of Authorizing Virtual Machinesz/VM V5R4.0 ConnectivitySC24-6080-07

The following examples show how to explicitly authorize server virtual machines, the AVS virtual machine, and requester virtual machines.
Example 1: Figure 92 is an example of an explicitly authorized TSAF collection involving two z/VM systems sharing global resources. The entries within each box represent the CP directory entries for each CMS virtual machine.
Figure 92. TSAF Collection with Authorized Global Resource Managers and User Programs

In Figure 92, users have the following authorization:
USERa on VMSYS1 can connect only to RES2 on VMSYS2.
USERb on VMSYS1 can connect only to RES1 on VMSYS1.
USERc on VMSYS2 can connect to RES1 on VMSYS1 and to RES2 on VMSYS2.
USERd on VMSYS2 can connect only to RES2 on VMSYS2.

Example 2: Figure 93 shows a TSAF collection in which the server and requester virtual machines are explicitly authorized to share local and private resources. The entries within each box represent the CP directory entries of each CMS virtual machine.
Figure 93. TSAF Collection with Authorized Local and Private Resource Managers and User Programs
In this figure, users have the following authorization:

USERa on VMSYS3 can connect only to RMGR4 on VMSYS4 to access a private resource managed by RMGR4.
USERb on VMSYS3 can connect only to RES1 on VMSYS3.
USERc on VMSYS4 can connect only to RMGR4 on VMSYS4 to access a private resource managed by RMGR4.

Example 3: Figure 94 shows an explicitly authorized TSAF collection involving two z/VM systems and one AVS virtual machine. The entries within each box represent the CP directory entries for each CMS virtual machine and the AVS virtual machine.
Figure 94. TSAF Collection with an AVS Virtual Machine

In this figure, users have the following authorization:
USERa on VMSYS5 can only connect out to the SNA network through GAT2 on VMSYS6.
USERb on VMSYS5 can only connect out to the SNA network through GAT1 on VMSYS6.
USERc on VMSYS6 can connect out to the SNA network through any gateway defined on VMSYS6 because it is authorized to connect to any virtual machine, resource, or gateway on the local system.

2009-07-02T04:02:00.000-07:00

SYSTEM COMPONENTS

Process Management

A process is a program in execution. A process needs certain resources, including CPU time, memory, files, and I/O devices, to accomplish its task. The operating system is responsible for the following activities in connection with process management.
*Process creation and deletion.
*process suspension and resumption.
*Provision of mechanisms for:
=>a. process synchronization
=>b. process communication

Main-Memory Management

Memory is a large array of words or bytes, each with its own address. It is a repository of quickly accessible data shared by the CPU and I/O devices. Main memory is a volatile storage device. It loses its contents in the case of system failure. The operating system is responsible for the following activities in connections with memory management:
*Keep track of which parts of memory are currently being used and by whom.
*Decide which processes to load when memory space becomes available.
*Allocate and deallocate memory space as needed.

File Management

A file is a collection of related information defined by its creator. Commonly, files represent programs (both source and object forms) and data.

The operating system is responsible for the following activities in connections with file management:
*File creation and deletion.
*Directory creation and deletion.
*Support of primitives for manipulating files and directories.
*Mapping files onto secondary storage.
*File backup on stable (nonvolatile) storage media.

I/O System Management

=> I/O system consists of:
*A buffer-caching system
*A general device-driver interface
*Drivers for specific hardware devices

Secondary-Storage Management

Since main memory (primary storage) is volatile and too small to accommodate all data and programs permanently, the computer system must provide secondary storage to back up main memory. Most modern computer systems use disks as the principle on-line storage medium, for both programs and data.

The operating system is responsible for the following activities in connection with disk management:

*Free space management
*Storage allocation
*Disk scheduling

Networking (Distributed Systems)

A distributed system is a collection processors that do not share memory or a clock. Each processor has its own local memory. The processors in the system are connected through a communication network. Communication takes place using a protocol. A distributed system provides user access to various system resources.
Access to a shared resource allows:
*Computation speed-up
*Increased data availability
*Enhanced reliability

Protection System

Protection refers to a mechanism for controlling access by programs, processes, or users to both system and user resources.
The protection mechanism must:
*distinguish between authorized and unauthorized usage.
*specify the controls to be imposed.
*Provide a means of enforcement.

Command-Interpreter System

Many commands are given to the operating system by control statements which deal with:
process creation and management
*I/O handling

*secondary-storage management
*main-memory management
*file-system access
*protection
*networking

The program that reads and interprets control statements is called variously:
*command-line interpreter
*shell (in UNIX)

2009-07-02T04:00:00.001-07:00

OPERATING SYSTEM SERVICES

Operating systems are responsible for providing essential services within a computer system:
Initial loading of programs and transfer of programs between secondary storage and main memory

Program execution – system capability to load a program into memory and to run it.
I/O operations – since user programs cannot execute I/O operations directly, the operating system must provide some means to perform I/O.
File-system manipulation – program capability to read, write, create, and delete files.
Communications – exchange of information between processes executing either on the same computer or on different systems tied together by a network. Implemented via shared memory or message passing.
Error detection – ensure correct computing by detecting errors in the CPU and memory hardware, in I/O devices, or in user programs.

2009-07-02T03:32:00.000-07:00

SYSTEM CALLS

Process control

Process control is a statistics and engineering discipline that deals with architectures, mechanisms, and algorithms for controlling the output of a specific process.

For example, heating up the temperature in a room is a process that has the specific, desired outcome to reach and maintain a defined temperature (e.g. 20°C), kept constant over time. Here, the temperature is the controlled variable. At the same time, it is the input variable since it is measured by a thermometer and used to decide whether to heat or not to heat. The desired temperature (20°C) is the setpoint. The state of the heater (e.g. the setting of the valve allowing hot water to flow through it) is called the manipulated variable since it is subject to control actions.
A commonly used control device called a programmable logic controller, or a PLC, is used to read a set of digital and analog inputs, apply a set of logic statements, and generate a set of analog and digital outputs. Using the example in the previous paragraph, the room temperature would be an input to the PLC. The logical statements would compare the setpoint to the input temperature and determine whether more or less heating was necessary to keep the temperature constant. A PLC output would then either open or close the hot water valve, an incremental amount, depending on whether more or less hot water was needed. Larger more complex systems can be controlled by a Distributed Control System (DCS) or SCADA system.
In practice, process control systems can be characterized as one or more of the following forms:
Discrete – Found in many manufacturing, motion and packaging applications. Robotic assembly, such as that found in automotive production, can be characterized as discrete process control. Most discrete manufacturing involves the production of discrete pieces of product, such as metal stamping.
Batch – Some applications require that specific quantities of raw materials be combined in specific ways for particular durations to produce an intermediate or end result. One example is the production of adhesives and glues, which normally require the mixing of raw materials in a heated vessel for a period of time to form a quantity of end product. Other important examples are the production of food, beverages and medicine. Batch processes are generally used to produce a relatively low to intermediate quantity of product per year (a few pounds to millions of pounds).
Continuous – Often, a physical system is represented though variables that are smooth and uninterrupted in time. The control of the water temperature in a heating jacket, for example, is an example of continuous process control. Some important continuous processes are the production of fuels, chemicals and plastics. Continuous processes, in manufacturing, are used to produce very large quantities of product per year(millions to billions of pounds).

File Management

Also referred to as simply a file system or filesystem. The system that an operating system or program uses to organize and keep track of files.

Device Management

Device Management is a set of technologies, protocols and standards used to allow the remote management of mobile devices, often involving updates of firmware over the air (FOTA). The network operator, handset OEM or in some cases even the end-user (usually via a web portal) can use Device Management, also known as Mobile Device Management, or MDM, to update the handset firmware/OS, install applications and fix bugs, all over the air. Thus, large numbers of devices can be managed with single commands and the end-user is freed from the requirement to take the phone to a shop or service center to refresh or update.

Information Maintenance

2009-07-02T03:06:00.000-07:00

SYSTEM STRUCTURE

Simple Structure

These are structures with low degree of departmentalisation and a wide span of control. The authority is largely centralised in a single person with very little formalisation. It is also called 'flat structure'. It usually has only two or three vertical levels, a flexible set of employees, and generally one person in whom the power of decision-making is invested. This simple structure is most widely practiced in small business settings where manager and owner happens to be the same person. Its advantage lies in its simplicity. This makes it responsive, fast, accountable and easy to maintain. However, it becomes grossly inadequate as and when the organisation grows in size. Such a simple structure is becoming popular becauseof its flexibility, responsiveness and high degree of adaptability to change.

Layered approach

The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface.
With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers.

MS-DOS Layered Structure

2009-06-25T03:31:00.000-07:00

2.STORAGE HIERARCHY

Caching:

->In computer science, a cache (pronounced /kæʃ/) is a collection of data duplicating original values stored elsewhere or computed earlier, where the original data is expensive to fetch (owing to longer access time) or to compute, compared to the cost of reading the cache. In other words, a cache is a temporary storage area where frequently accessed data can be stored for rapid access. Once the data is stored in the cache, it can be used in the future by accessing the cached copy rather than re-fetching or recomputing the original data.

->Most modern microprocessors contain some form of instruction and data caching where a small but fast bit of memory is used to speed up access to main memory. At its simplest level, a cache can pre-load blocks of memory from main memory so that the processor need not stall when performing a load. This is possible because (a) a processor usually accesses sequential memory locations and (b) loading more than one sequential memory location at the same time is faster than loading each sequential memory location one by one. Hence when the processor accesses an uncached bit of memory, the cache reads a full cache line in the hope it will be used (which it usually is).
Again at its simplest level, a cache must be write-through cache whenever the processor performs a write to main memory. Quite simply, when the write is performed, the relevant cache entry is updated, and a write to main memory is issued. One could say that cache coherency has been maintained ie; the cache accurately reflects the contents of main memory.

Coherency and Consistency:

->(Or "cache consistency") /kash koh-heer'n-see/ The synchronisation of data in multiple caches such that reading a memory location via any cache will return the most recent data written to that location via any (other) cache.Some parallel processors do not cache accesses to shared memory to avoid the issue of cache coherency. If caches are used with shared memory then some system is required to detect when data in one processor's cache should be discarded or replaced because another processor has updated that memory location. Several such schemes have been devised. Coherency defines what value is returned on a read.
->Consistency defines when it is available.

2009-06-25T02:56:00.000-07:00

3.HARDWARE PROTECTION

Dual-mode Operation:

Sharing system resources requires operating system to ensurethat an incorrect program cannot cause other programs toexecute incorrectly.
• Provide hardware support to differentiate between at least twomodes of operations.
1. User mode – execution done on behalf of a user.
2. Monitor mode (also supervisor mode or system mode) –execution done on behalf of operating system.

Mode bit added to computer hardware to indicate the currentmode: monitor (0) or user (1).

• When an interrupt or fault occurs hardware switches to monitormodeuser monitorinterrupt/faultset user mode.

• Privileged instructions can be issued only in monitor mode.

I/O Protection:

->All I/O instructions are privileged instructions.

->Must ensure that a user program could never gain control ofthe computer in monitor mode (i.e., a user program that, aspart of its execution, stores a new address in the interruptvector).

Memory Protection:

Must provide memory protection at least for the interrupt vectorand the interrupt service routines.
• In order to have memory protection, add two registers thatdetermine the range of legal addresses a program may access:
–> base register – holds the smallest legal physical memoryaddress.
– >limit register – contains the size of the range.
• Memory outside the deﬁned range is protected.

CPU Protection:

->To prevent a user programs gets stuck in infinite loop and never returning back to the os

2009-06-25T02:00:00.000-07:00

1.STORAGE STRUCTURE

Main memory:

Refers to physical memory that is internal to the computer. The word main is used to distinguish it from external mass storage devices such as disk drives. Another term for main memory is RAM.

Magnetic disk:

A memory device, such as a floppy disk or a hard disk, that is covered with a magnetic coating. Digital information is stored on magnetic disks in the form of microscopically small, magnetized needles, each of which encodes a single bit of information by being polarized in one direction (representing 1) or the other (representing 0).

Moving head disk mechanism:

Magnetic tapes:

Magnetic tape is a medium for magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of plastic. Nearly all recording tape is of this type, whether used for recording audio or video or for computer data storage. It was originally developed in Germany, based on the concept of magnetic wire recording. Devices that record and playback audio and video using magnetic tape are generally called tape recorders and video tape recorders respectively. A device that stores computer data on magnetic tape can be called a tape drive, a tape unit, or a streamer.
Magnetic tape revolutionized the broadcast and recording industries. In an age when all radio (and later television) was live, it allowed programming to be prerecorded. In a time when gramophone records were recorded in one take, it allowed recordings to be created in multiple stages and easily mixed and edited with a minimal loss in quality between generations. It is also one of the key enabling technologies in the development of modern computers. Magnetic tape allowed massive amounts of data to be stored in computers for long periods of time and rapidly accessed when needed.

2009-06-24T18:41:00.000-07:00

1.Bootstrap Program
In computing, booting is a bootstrapping process that starts operating systems when the user turns on a computer system. Most computer systems can only execute code found in the memory (ROM or RAM); modern operating systems are mostly stored on hard disk drives, LiveCDs and USB flash drive. Just after a computer has been turned on, it doesn't have an operating system in memory. The computer's hardware alone cannot perform complicated actions of the operating system, such as loading a program from disk on its own; so a seemingly irresolvable paradox is created: to load the operating system into memory, one appears to need to have an operating system already installed.

2.Difference of interrupt and trap and thier use.
Trap is actually a software generated interrupt caused either by an error (for example division by zero, invalid memory access etc.), or by an specific request by an operating system service generated by a user program. Trap is sometimes called Exception. The hardware or software can generate these interrupts. When the interrupt or trap occurs, the hardware therefore, transfer control to the operating system which first preserves the current state of the system by saving the current CPU registers contents and program counter's value. after this, the focus shifts to the determination of which type of interrupt has occured. For each type of interrupt, separate segmants of code in the operating system determine what action should be taken and thus the system keeps on functioning by executing coputational instruction, I/O instruction, torage instruction etc.

3. Monitor mode,
or RFMON (Radio Frequency Monitor)mode,allows a computer with a wireless network interface card (NIC) to monitor all traffic received from the wireless network. Unlike promiscuous mode, which is also used for packet sniffing, monitor mode allows packets to be captured without having to associate with an access point or ad-hoc network first. Monitor mode only applies to wireless networks, while promiscuous mode can be used on both wired and wireless networks. Monitor mode is one of the six modes that 802.11 wireless cards can operate in: Master (acting as an access point), Managed (client, also known as station), Ad-hoc, Mesh, Repeater, and Monitor mode.

4.User mode
In User mode, the executing code has no ability to directly access hardware or reference memory. Code running in user mode must delegate to system APIs to access hardware or memory. Due to the protection afforded by this sort of isolation, crashes in user mode are always recoverable. Most of the code running on your computer will execute in user mode.

5.Device Status Table

Device-status table contains entry for each I/O deviceindicating its type, address, and state.

6.Direct memory access
Direct memory access (DMA) is a feature of modern computers and microprocessors that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit. Many hardware systems use DMA including disk drive controllers, graphics cards, network cards and sound cards. DMA is also used for intra-chip data transfer in multi-core processors, especially in multiprocessor system-on-chips, where its processing element is equipped with a local memory (often called scratchpad memory) and DMA is used for transferring data between the local memory and the main memory. Computers that have DMA channels can transfer data to and from devices with much less CPU overhead than computers without a DMA channel. Similarly a processing element inside a multi-core processor can transfer data to and from its local memory without occupying its processor time and allowing computation and data transfer concurrency.

7.Difference of RAM and DRAM
Random-access memory (usually known by its acronym, RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order (i.e., at random). The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.[1] By contrast, storage devices such as tapes, magnetic discs and optical discs rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than data transfer, and the retrieval time varies based on the physical location of the next item. The word RAM is often associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off. Many other types of memory are RAM, too, including most types of ROM and flash memory called NOR-Flash.

Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory.

8.Main memory
Refers to physical memory that is internal to the computer. The word main is used to distinguish it from external mass storage devices such as disk drives. Another term for main memory is RAM.

9.Magnetic Disk
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. As of 2009, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the term magnetic storage is preferred and in the field of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference.

10.Storage Hierarchy
The hierarchical arrangement of storage in current computer architectures is called the memory hierarchy. It is designed to take advantage of memory locality in computer programs. Each level of the hierarchy has the properties of higher bandwidth, smaller size, and lower latency than lower levels.Most modern CPUs are so fast that for most program workloads, the locality of reference of memory accesses and the efficiency of the caching and memory transfer between different levels of the hierarchy are the practical limitation on processing speed. As a result, the CPU spends much of its time idling, waiting for memory I/O to complete. This is sometimes called the space cost, as a larger memory object is more likely to overflow a small/fast level and require use of a larger/slower level.

2009-06-22T01:57:00.000-07:00

6.Differentiate client-server systems and peer-to-peer systems.
Client-server computing or networking is a distributed application architecture that partitions tasks or work loads between service providers (servers) and service requesters, called clients.[1] Often clients and servers operate over a computer network on separate hardware. A server is a high-performance host that is a registering unit and shares its resources with clients. A client does not share any of its resources, but requests a server's content or service function. Clients therefore initiate communication sessions with servers which await (listen to) incoming requests.
Peer-to-peer (P2P) networking is a method of delivering computer network services in which the participants share a portion of their own resources, such as processing power, disk storage, network bandwidth, printing facilities. Such resources are provided directly to other participants without intermediary network hosts or servers.[1] Peer-to-peer network participants are providers and consumers of network services simultaneously, which contrasts with other service models, such as traditional client-server computing.

2009-06-22T01:51:00.000-07:00

5.Differentiate Symmetric Multiprocessing and Asymmetric Multiprocessing.
Symmetric multiprocessing treats all processors as equals, and I/O can be processed on any CPU. Asymmetric multiprocessing has one master CPU and the remainder CPUs are slaves. The master distributes tasks among the slaves, and I/O is usually done by the master only. Multiprocessors can save money, by not duplicating power supplies, housings, and peripherals. They can execute programs more quickly, and can have increased reliability. They are also more complex in both hardware and software than uniprocessor systems.

2009-06-22T01:49:00.000-07:00

4.Advantages of Parallel Systems?
Parallel systems usually give results which fall somewhere between pure plurality/majority and pure PR systems. One advantage is that, when there are enough PR seats, small minority parties which have been unsuccessful in the plurality/majority elections can still be rewarded for their votes by winning seats in the proportional allocation. In addition, a Parallel system should, in theory, fragment the party system less than a pure PR electoral system.

2009-06-22T01:43:00.000-07:00

3.What's the difference between Batch systems, Multiprgrammed systems, and time-sharing systems?
Batch. A job was originally presented to the machine (and its human operator) in the form of a set of cards - these cards held information according to how ``punched'' out of the cardboard. The operator grouped all of the jobs into various batches with similar characteristics before running them(all the quick jobs might run, then the slower ones, etc.).While multiprogrammed systems used resources more efficiently i.e. minimized CPU idle time, a user could not interact with a program. By having the CPU switch between jobs at relatively short intervals, we can obtain an interactive system.That is, a system in which a number of users are sharing the CPU (or other critical resource) with a timing interval small enough not to be noticed e.g. no more than 1 second. We say that a time-sharing system uses CPU scheduling and multiprogramming to provide each user with a small portion of a time-shared computer and Time-sharing is sharing a computing resource among many users by multitasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major historical shift in the history of computing. By allowing a large number of users to interact simultaneously on a single computer, time-sharing dramatically lowered the cost of providing computing, while at the same time making the computing experience much more interactive.

2009-06-22T01:39:00.001-07:00

1.What is the difference of OS in terms of user's view and system's view?
User's view:
Operating system is designed mostly for ease of use.The operating system is designed mostly for ease of use, with some attention paid to performance, and none paid to resource utilization.
System View:
We can view an operating system as a resource allocator. The operating system acts as the manager of these resources.An operating system can also be viewed as a control program that manages the execution of user programs to prevent errors and improper use of the computer.

2009-06-21T00:12:00.000-07:00

f. HANDHELD
A Mobile operating system, also known as , a Mobile OS, a Mobile platform, or a Handheld operating system, is the operating system that controls a mobile device—similar in principle to an operating system such as Linux or Windows that controls a desktop computer.
However, they are currently somewhat simpler, and deal more with the wireless versions of broadband and local connectivity, mobile multimedia formats, and different input methods.The ongoing shift away from voice-intensive cellular technology to data-intensive mobile broadband is a significant issue for many large industriesMobile platforms are in the nascent stage, and any projection regarding the market growth is hard to make at the present time. It is noteworthy that Intel is taking the initiative to focus on portable devices other than mobile phones. They are Mobile Internet Devices (MID) and Ultra-Mobile PC (UMPC). Meantime, Palm abandoned its plan to develop Foleo, which was to be a companion device for a smartphone.

2009-06-21T00:03:00.000-07:00

2.GOALS OF THE OPERATING SYSTEM:

It is easier to define an operating system by what it does than what it is, but even this can be tricky. The primary goal of some operating system is convenience for the user. The primary goal of other operating system is efficient operation of the computer system. Operating systems and computer architecture have influenced each other a great deal. To facilitate the use of the hardware, researchers developed operating systems. Users of the operating systems then proposed changes in hardware design to simplify them. In this short historical review, notice how identification of operating-system problems led to the introduction of new hardware features.

2009-06-20T23:42:00.000-07:00

7. Differentiate the design issues of OS between a stand alone PC and a workstation connected to a network

stand-alone PC
A desktop or laptop computer that is used on its own without requiring a connection to a local area network (LAN) or wide area network (WAN). Although it may be connected to a network, it is still a stand-alone PC as long as the network connection is not mandatory for its general use.

workstation
A significant segment of the desktop market are computers expected to perform as workstations, but using PC operating systems and components. PC component manufacturers will often segment their product line, and market premium components which are functionally similar to the cheaper "consumer" models but feature a higher level of robustness and/or performance. Notable examples of this are the AMD Opteron, Intel Xeon processors, and the ATI FireGL and Nvidia Quadro graphics processors.A workstation class PC may have some of the following features:
support for ECC memory
a larger number of memory sockets which use registered (buffered) modules
multiple processors
multiple displays
run a "business" or "professional" operating system version

2009-06-18T02:21:00.001-07:00

8.Define the essential properties of the following types of OS:

a.BATCH

Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequencer. Performance is increased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operation, spooling, and multiprogramming. Batch is good for executing large jobs that need little interaction; it can be submitted and picked up later.

b.TIME SHARING

Uses CPU scheduling and multiprogramming to provide economical interactive use of a system. The CPU switches rapidly from one user to another. Instead of having a job de?ned by spooled card images, each program reads its next control card from the terminal, and output is normally printed immediately to the screen.

c.REAL TIME

Often used in a dedicated application. The system reads information from sensors and must respond within a ?xed amount of time to ensure correct performance.

d.NETWORK

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network.
A computer network is a collection of computers and devices connected to each other. The network allows computers to communicate with each other and share resources and information.

e.DISTRIBUTED

Distributes computation among several physical processors. The processors do not share memory or a clock. Instead, each processor has its own local memory. They communicate with each other through various communication lines, such as a high-speed bus or telephone line