Monday, November 16, 2009

Windows Xp Registy Tips

Opening Ports or Adding Allowed Programs with SP2's Firewall

1.Click on Start / Run
2.Enter in firewall.cpl
3.Click on the Exceptions tab
Adding a Port for Internet Access:
1.Click on the Add Port button
2.Name it whatever you want
3.Enter in the ports you want to open
Adding a Program for Internet Access
1.Click on Add Program... button
2.A list of all installed programs will be displayed
3.Highlight the one you want to include for Internet access
4.Click on the OK button

Autoexec.nt or Config.nt Errors

If you are getting errors similar to:
The system file is not suitable for running MS-DOS and Microsoft Windows applications. Choose 'Close' to terminate the application.
Try copying the file from \windows\repair directory to the one that is in the \windows\system32 directory.

Common Control Panel Applets

The follow are some common Control Panel Applets that are located in the \windows\system32 directory.
If you find yourself using any of these frequently, then you can simply make shortcuts to them on your desktop.

appwiz.cpl >>Add/Remove Programs
desk.cpl >> Display Properties
firewall.cpl >> Firewall Settings
inetcpl.cpl >> Internet Options
mmsys.cpl >> Sound and Audio
ncpa.cpl >> Network Connections
nusrmgr.cpl >> User Accounts
powercfg.cpl >> Power Options
sysdm.cpl >>System Properties
wscui.cpl >> Security Center
wuaucpl.cpl >> Automatic Updates Configuration
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Windows Explorer Opens Search Companion Rather than the Folder

If the Windows Explorer opens up the Search Companion rather than opening up the actual folder, the default setting for opening a folder is changed.
To correct this:
Start Regedit
Go to HKEY_CLASSES_ROOT \ Directory \ shell
Edit the default value to be explorer or none

Guest Only Network Access

If you try and connect to an XP computer and are shown a logins screen with only the computername/Guest,
You may need to change one of the Local Security Policies:
Got to Control Panel - Administrative Tools
Go to Local Policies - Security Options
Check teh Network access: Sharing and security model for local accounts
Set it to Classic - local users authenticate as themselves

Hiding a XP Computer from Network Neighborhood

If you want to share files from a XP computer,
yet want to remove it from showing up in the Network Neighborhood,
Run net config server /hidden:yes

Easy Way to Share Multiple Folders

If you need to share multiple folders, running the program SHRPUBW.EXE will bring up a simple dialog box to let you:
Browse to the folder you want to share
Enter in a Share name
Ender in a Share description
Set permissions. Several choices are available
Restart the process from within the same program
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Not Viewing Zip Files as Folders

If you want to turn of WindowsXP showing Zip files as folders,
just run:
regsvr32 /u zipfldr.dll

Setting Capslock, Numlock, Scroll Lock

If you want to set the startup state for any or all of these keys,
you just need to edit the registry.
Start Regedit
Go to HKEY_CURRENT_USER \ Control Panel \ Keyboard
Open InitialKeyboardIndicators
Change the value to one of the following numbers
0 - All Keys off
1 - Caps Lock on
2 - Num Lock on
4 - Scroll Lock on
For multiple keys, add their values:
3 - Caps Lock and Num Lock on
5 - Caps Lock and Scroll Lock on
6 - Num Lock and Scroll Lock on
7 - Caps Lock, Num Lock, and Scroll Lock on
Log off and back on again

Restoring Desktop Icon to the Quicklaunch Bar

If you mistakenly deleted the icon for the Desktop on the Quicklaunch toolbar
Go to C:\Documents and Settings\user_name\Application Data\Microsoft\Internet Explorer\Quick Launch
(where user_name is replaced by your login name)
Create a Text file called ShowDesktop.SCF with the following contents:
[Shell]
Command=2
IconFile=explorer.exe,3
[Taskbar]
Command=ToggleDesktop
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Network Access After Norton Anti-Virus Install

Sometimes you can't access a WinXP computer after installing Norton Anti-Virus.
There might be a variety of errors at the other computer depending on the operating system.
On the XP computer, in the Event Viewer / System log, there will be the following error:
The server's configuration parameter "irpstacksize" is too small for the server to use a local device.
Start Regedit
Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters
Edit the IRPStackSize
Give it a value of 15
Reboot the computer

Configure for Auto-Logon

If you are the only person using the computer and what to have it automatically log you on,
Start / Run / "control userpasswords2" - no quotes
Uncheck User must enter a user name and password to use this computer

Services You Can Disable

There are quite a few services you can disable from starting automatically.
This would be to speed up your boot time and free resources.
They are only suggestions so I suggestion you read the description of each one when you run Services
and that you turn them off one at a time.

Some possibilities are:
Alerter - Sends alert messages to specified users that are connected to the server computer.
Application Management - Allows software to tap directly into the Add/Remove Programs feature via the Windows Installer technology.
Background Intelligent Transfer Service - The Background Intelligent Transfer service is used by programs (such as Windows AutoUpdate) to download files by using spare bandwidth.
Clipbook - ClipBook permits you to cut and paste text and graphics over the network.
Error Reporting Service - Allows applications to send error reports to Microsoft in the event of an application fault.
Fast User Switching - Windows XP allows users to switch quickly between accounts, without requiring them to log off.
Help and Support - Allows the XP Built-in Help and Support Center to run.
IMAPI CD-Burning COM Service - You don't need this if you have other software to create CDs.
Indexing Service - Indexes contents and properties of files on local and remote computers; provides rapid access to files through flexible querying language.
IP SEC - Manages IP security policy and starts the ISAKMP/Oakley (IKE) and the IP security driver. If you are not on a domain, you likely don't need this running.
Messenger - Transmits net send and Alerter service messages between clients and servers. This is how a lot of pop-up windows start appearing on your desktop.
Net Logon - Supports pass-through authentication of account logon events for computers in a domain. If you are not on a domain, you don't need this running
Network DDE - Provides network transport and security for Dynamic Data Exchange (DDE) for programs running on the same computer or on different computers.
NT LM Security Support Provider - Provides security to remote procedure call (RPC) programs that use transports other than named pipes.
Performance Logs and Alerts - Collects performance data from local or remote computers based on preconfigured schedule parameters, then writes the data to a log or triggers an alert. If you don't need to monitor your performance logs, then you don't need this service.
Portable Media Serial Number - Retrieves the serial number of any portable music player connected to your computer
QOS RSVP - Provides network signaling and local traffic control setup functionality for QoS-aware programs and control applets.
Remote Desktop Help Session Manager - Manages and controls Remote Assistance. If you are not using Remote Desktop you don't need this service.
Remote Registry - Enables remote users to modify registry settings on this computer.
Routing & Remote Access - Offers routing services to businesses in local area and wide area network environments. Allows dial-in access.
Secondary Login - Enables starting processes under alternate credentials. This is what allows you to run an application as another user.
Smart Card - Manages access to smart cards read by this computer.
Smart Card Helper - Enables support for legacy non-plug and play smart-card readers used by this computer.
SSDP Discovery Service - Enables discovery of UPnP devices on your home network.
TCP/IP NetBIOS Helper - Enables support for NetBIOS over TCP/IP (NetBT) service and NetBIOS name resolution. This should not be needed in today's network environment.
Telnet - Enables a remote user to log on to this computer and run programs, and supports various TCP/IP Telnet clients.
Uninterruptible Power Supply Service - Manages an uninterruptible power supply (UPS) connected to the computer.
Universal Plug and Play Device Host - Provides support to host Universal Plug and Play devices
Upload Manager - Manages synchronous and asynchronous file transfers between clients and servers on the network.
Volume Shadow Copy Service - Manages and implements Volume Shadow Copies used for backup and other purposes.
Web Client - Enables Windows-based programs to create, access, and modify non-local files across the Internet.
Wireless Zero Configuration - Provides automatic configuration for the 802.11 adapters
WMI Performance Adapter - Provides performance library information from WMI HiPerf providers.

Cleaning the Prefetch Directory

WindowsXP has a new feature called Prefetch. This keeps a shortcut to recently used programs.
However it can fill up with old and obsolete programs.
To clean this periodically go to:
Star / Run / Prefetch
Press Ctrl-A to highlight all the shorcuts
Delete them
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Not Displaying Logon, Logoff, Startup and Shutdown Status Messages

To turn these off:
Start Regedit
Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
If it is not already there, create a DWORD value named DisableStatusMessages
Give it a value of 1

Repair Install

If XP is corrupted to the point where none of the previous solutions get it to boot,
you can do a Repair Install that might work as well as keep the current settings.
Make sure you have your valid WindowsXP key.
The whole process takes about half an hour depending on your computer
If you are being prompted for the administrator's password, you need to choose the 2nd repair option, not the first.
Insert and boot from your WindowsXP CD
At the second R=Repair option, press the R key
This will start the repair
Press F8 for I Agree at the Licensing Agreement
Press R when the directory where WindowsXP is installed is shown. Typically this is C:\WINDOWS
It will then check the C: drive and start copying files
It will automatically reboot when needed. Keep the CD in the drive.
You will then see the graphic part of the repair that is like during a normal install of XP (Collecting Information, Dynamic Update, Preparing Installation, Installing Windows, Finalizing Installation)
When prompted, click on the Next button
When prompted, enter your XP key
Normally you will want to keep the same Workgroup or Domain name
The computer will reboot
Then you will have the same screens as a normal XP Install
Activate if you want (usually a good idea)
Register if you want (but not necessary)
Finish
At this point you should be able to log in with any existing accounts.
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NTOSKRNL Missing or Corrupt

If you get an error that NTOSKRNL not found:
Insert and boot from your WindowsXP CD.
At the first R=Repair option, press the R key
Press the number that corresponds to the correct location for the installation of Windows you want to repair.
Typically this will be #1
Change to the drive that has the CD ROM.
CD i386
expand ntkrnlmp.ex_ C:\Windows\System32\ntoskrnl.exe
If WindowsXP is installed in a different location, just make the necessary change to C:\Windows
Take out the CD ROM and type exit

HAL.DLL Missing or Corrupt

If you get an error regarding a missing or corrupt hal.dll file, it might simply be the BOOT.INI file on the root of the C: drive that is misconfigured
Insert and boot from your WindowsXP CD.
At the first R=Repair option, press the R key
Press the number that corresponds to the correct location for the installation of Windows you want to repair.
Typically this will be #1
Type bootcfg /list to show the current entries in the BOOT.INI file
Type bootcfg /rebuild to repair it
Take out the CD ROM and type exit

Corrupted or Missing \WINDOWS\SYSTEM32\CONFIG

If you get the error:
Windows could not start because the following files is missing or corrupt
\WINDOWS\SYSTEM32\CONFIG\SYSTEM or \WINDOWS\SYSTEM32\CONFIG\SOFTWARE
Insert and boot from your WindowsXP CD.
At the first R=Repair option, press the R key
Press the number that corresponds to the correct location for the installation of Windows you want to repair.
Typically this will be #1
Enter in the administrator password when requested
cd \windows\system32\config
Depending on which section was corrupted:
ren software software.bad or ren system system.bad
Depending on which section was corrupted
copy \windows\repair\system
copy \windows\repair\software
Take out the CD ROM and type exit
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NTLDR or NTDETECT.COM Not Found

If you get an error that NTLDR is not found during bootup,
If you have FAT32 partitions, it is much simpler than with NTFS.
Just boot with a Win98 floppy and copy the NTLDR or NTDETECT.COM files
from the i386 directory to the root of the C:\ drive.
For NTFS:
Insert and boot from your WindowsXP CD.
At the first R=Repair option, press the R key
Press the number that corresponds to the correct location for the installation of Windows you want to repair.
Typically this will be #1
Enter in the administrator password when requested
Enter in the following commands (X: is replaced by the actual drive letter that is assigned to the CD ROM drive.
COPY X:\i386\NTLDR C\:
COPY X:\i386\NTDETECT.COM C:\
Take out the CD ROM and type exit

Bringing Up the Shutdown Dialog Box

Create a new txt file somewhere on your system, open it and put in this one line:
(new ActiveXObject("Shell.Application")).ShutdownWindows();
Save and Close the file. Change the extension to js and your got it.
You can make a shortcut to that file to make it easy to shut down your system.

Hiding the Last User Logged On

If you use the standard NT style of login and want to hide the last user:
Start the Group Policy Editor (gpedit.msc)
Go to Computer Configuration / Windows Settings / Security Settings / Local Policies / Security Options
Scroll down to Interactive logon: Do not display last user name
Set it to Enable
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Poweroff at Shutdown

If your computer does not turn off the power when doing a shutdown,
you may need to edit the registry. I have all the correct BIOS and Power settings and still needed to do this.
Start Regedit
Go to HKEY_CURRENT_USER\Control Panel\Desktop
Edit the key PowerOffActive and give it a value of 1
You can do the same in HKEY_USERS\.DEFAULT\Control Panel\Desktop

Remembering Folder Settings

If XP does not remember your folder settings, delete or rename the following registry keys
[HKEY_CURRENT_USER\Software\Microsoft\Windows\ShellNoRoam\BagMRU]
[HKEY_CURRENT_USER\Software\Microsoft\Windows\ShellNoRoam\Bags]

Preventing Applications from Stealing the Focus

To prevent applications from stealing the focus from the window you are working
Start Regedit
Go to HKEY_CURRENT_USER \ Control Panel \ Desktop
Edit the key ForegroundLockTimeout
Give it a value of 00030d40

Disable Explorer Thumbnail View

If you want disable the Explorer's ability to show the Thumbnail View ,
Start Regedit
Go to HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Explorer \ Advanced \
Change ClassicViewState to 1
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Disable Shared Documents

To disable the Shared Documents folder that shows up on the network
Start Regedit
Go to HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Policies \ Explorer \
Create a new DWORD Value
Give it the name NoSharedDocuments
Give it a value of 1
Log off or reboot

Removing Thumbs.db Files

When viewing a folder with the Thumbnail view, WindowsXP creates a thumbs.db file.
This is a cache of the current pictures in that directory.
If you want to turn this feature off and save a little disk space
Start the Windows Explorer
Go to Tools / Folder Options / View
In the first section under Files and Folders, check Do not cache thumbnails
Now you can search for the thumbs.db file on your computer and remove them. No more should be created.

Enable / Disable the Task Manager

Start Regedit
Go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
Create the Dword value DisableTaskMgr
Give it a value of 0 to enable it
Give it a vaule of 1 to disable it
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Clearing the Page File on Shutdown

Another way to set the computer to clear the pagefile without directly editing the registry is:
Click on the Start button
Go to the Control Panel
Administrative Tools
Local Security Policy
Local Policies
Click on Security Options
Right hand menu - right click on "Shutdown: Clear Virtual Memory Pagefile"
Select "Enable"
Reboot

If you want to clear the page file on each shutdown:
Start Regedit
Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\ClearPageFileAtShutdown
Set the value to 1

No GUI Boot

If you don't need to see the XP boot logo,
Run MSCONFIG
Click on the BOOT.INI tab
Check the box for /NOGUIBOOT

Using the Classic Search in Explorer

If you prefer to use the classic search style in Explorer,
Start Regedit
Go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
Add a String Key called Use Search Asst
Give it a value of no
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Changing Drive Letters

If you want to change the letters assigned to your fixed or removable drives:
Right Click on My Computer
Select Manage
Select Disk Management
For a Fixed Disk:
Select it
Right click
Select Change Drive Letter and Path
Click on the Edit button
Enter in the letter you want to use
For a Removable Disk:
In the lower, right hand panel, right click on the Disk or CD ROM #
Select Change Drive Letter and Path
Click on the Edit button
Enter in the letter you want to use

Changing the Registered Owner

Start Regedit
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion
From there you can edit the name in the Registered Owner key

Decreasing Boot Time

Microsoft has made available a program to analyze and decrease the time it takes to boot to WindowsXP
The program is called BootVis
Uncompress the file.
Run BOOTVIS.EXE
For a starting point, run Trace / Next Boot + Driver Delays
This will reboot your computer and provide a benchmark
After the reboot, BootVis will take a minute or two to show graphs of your system startup.
Note how much time it takes for your system to load (click on the red vertical line)
Then run Trace / Optimize System
Re-Run the Next Boot + Drive Delays
Note how much the time has decreased
Mine went from approximately 39 to 30 seconds.
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Hide/Unhide Logon Names

If you want to hide or unhide the names of users that are displayed on the initial logon screen:
Start Regedit
Go to HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows NT \ CurrentVersion \ Winlogon \ SpecialAccounts \ UserList
Add a DWORD with the name of the user account you want to hide
Make sure it has a value of 0
If there is an existing account, you can unhide it by giving it a value of 1

WindowsXP Command Line Utilities

While there are a lot of command line utilities in WindowsXP, here are some that I have been using lately.
bootcfg - Configures, queries, or changes Boot.ini file settings.
driverquery - Displays a list of all installed device drivers and their properties.
getmac - Returns the media access control (MAC) address and list of network protocols associated with each address for all network cards in each computer
gpresult - Displays Group Policy settings and Resultant Set of Policy (RSOP) for a user or a computer
netsh - You can use commands in the Netsh Interface IP context to configure the TCP/IP protocol
schtasks - Schedules commands and programs to run periodically or at a specific time
systeminfo - Displays detailed configuration information about a computer and its operating system

Creating an Automated Install of WindowsXP

On the WindowsXP CP, in the SUPPORT\TOOLS directory,
there is a file called DEPLOY.CAB.
Extract the programs DEPLOY.CHM (help file) and SETUPMGR.EXE (main program)
Run SETUPMGR and answer the prompts.
This will create both a unattend.bat and unattend.txt file you can use for automated installs.
Note: The batch file might need some minor modification for file locations but it is fairly basic.

Disabling Hibernation

If you don't want to use up the disk space taken by Hibernation, or don't need to use it at all,
you can easily disable it.
Open up the Control Panel / Power Options icon
Click on the Hibernation icon
Uncheck Enable Hibernation
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Increasing System Performance

If you have 512 megs or more of memory, you can increase system performance
by having the core system kept in memory.
Start Regedit
Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\DisablePagingExecutive
Set the value to be 1
Reboot the computer

Common Command Console Utilities

WindowsXP comes with quite a few console utilities you can easily run from the command line:
Computer Management - compmgmt.msc
Disk Managment - diskmgmt.msc
Device Manager - devmgmt.msc
Disk Defrag - dfrg.msc
Event Viewer - eventvwr.msc
Shared Folders - fsmgmt.msc
Group Policies - gpedit.msc
Local Users and Groups - lusrmgr.msc
Performance Monitor - perfmon.msc
Resultant Set of Policies - rsop.msc
Local Security Settings - secpol.msc
Services - services.msc
Component Services - comexp.msc

Automatically Ending Non-Responsive Tasks

Start Regedit
Go to HKEY_CURRENT_USER\Control Panel\Desktop\AutoEndTasks
Set the value to be 1
In the same section, change the WaitToKillAppTimeout to the number of milliseconds you want.

Changing the Internet Explorer Title

Start Regedit
Go to HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main\Window Title
Enter what you want appear in the title bar

Changing Programs That Start Automatically

WindowsXP has a similar program, MSCONFIG, that was available in Windows98.
This allows you to view and change what programs are automatically started each time you log in.
The new version also allows you to view and edit the boot.ini file (as well as check for errors and use several advanced switches)

Windows Server and MS Exchange interview questions

  1. What is DHCP? How we configure DHCP?
  2. What are the ways to configure DNS & Zones?
  3. What are the types of backup? Explain each?
  4. What are Levels of RAID 0, 1, 5? Which one is better & why?
  5. What are FMSO Roles? List them.
  6. Describe the lease process of the DHCP server.
  7. Disaster Recovery Plan?
  8. What is scope & super scope?
  9. Differences between Win 2000 Server & Advanced Server?
  10. Logical Diagram of Active Directory? What is the difference between child domain & additional domain server?
  11. FTP, NNTP, SMTP, KERBEROS, DNS, DHCP, POP3 port numbers?
  12. What is Kerberos? Which version is currently used by Windows? How does Kerberos work?

Microsoft Exchange Server interview questions

  1. Distribution List?
  2. GAL, Routing Group, Stm files, Eseutil & ininteg - what are they used for?
  3. What is MIME & MAPI?
  4. List the services of Exchange Server 2000?
  5. How would you recover Exchange server when the log file is corrupted?

Sysadmin interview questions

  1. What is a level 0 backup?
  2. What is an incremental backup?
  3. What steps are required to perform a bare-metal recovery?
  4. Name key files or directories on a UNIX system that should always be backed up.
  5. Name key files or directories on a Windows system that should always be backed up.
  6. What is RAID 0?
  7. What is RAID 0+1? Why is it better than 0?
  8. What is RAID-5?
  9. Why would you NOT want to encapsulate a root directory with Veritas?
  10. What is concatenation?
  11. What is striping?
  12. What is a spindle?

1. Ans
Q1: level 0 backup is normal or full backup. A normal backup disregards
the archive bit in all files and backs up all files and folders selected, regardless of when they were modified. A normal backup is the most complete type of backup, and the only type of backup that can be used to back up the registry and other critical system files. A normal backup takes the longest amount of time to back up and recover. A normal backup clears the archive bit on all files after backing up.

Q2. An incremental backup is the quickest method for performing backups of data. An incremental backup only backs up files that have been created or modified (their archive bit is set to 1) since the last normal or incremental backup. An incremental backup also clears the archive bit (sets the archive bit back to 0) of all files that it backs up.

Q3. reinstall the os.
start -> run -> type “ntbackup” -> ok -> next -> select restore -> next -> select backup files -> next -> finish

Tech Interviews comment by manjunath

2. 11Q What is striping?

A technique for spreading data over multiple disk drives. Disk striping can speed up operations that retrieve data from disk storage. The computer system breaks a body of data into units and spreads these units across the available disks. Systems that implement disk striping generally allow the user to select the data unit size or stripe width.
Disk striping is available in two types. Single user striping uses relatively large data units, and improves performance on a single-user workstation by allowing parallel transfers from different disks. Multi-user striping uses smaller data units and improves performance in a multi-user environment by allowing simultaneous (or overlapping) read operations on multiple disk drives.

Tech Interviews comment by vamsi

  1. What are the basic functions of an operating system? - Operating system controls and coordinates the use of the hardware among the various applications programs for various uses. Operating system acts as resource allocator and manager. Since there are many possibly conflicting requests for resources the operating system must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls the user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.
  2. Why paging is used? - Paging is solution to external fragmentation problem which is to permit the logical address space of a process to be noncontiguous, thus allowing a process to be allocating physical memory wherever the latter is available.
  3. While running DOS on a PC, which command would be used to duplicate the entire diskette? diskcopy
  4. What resources are used when a thread created? How do they differ from those when a process is created? - When a thread is created the threads does not require any new resources to execute the thread shares the resources like memory of the process to which they belong to. The benefit of code sharing is that it allows an application to have several different threads of activity all within the same address space. Whereas if a new process creation is very heavyweight because it always requires new address space to be created and even if they share the memory then the inter process communication is expensive when compared to the communication between the threads.
  5. What is virtual memory? - Virtual memory is hardware technique where the system appears to have more memory that it actually does. This is done by time-sharing, the physical memory and storage parts of the memory one disk when they are not actively being used.
  6. What is Throughput, Turnaround time, waiting time and Response time? - Throughput – number of processes that complete their execution per time unit. Turnaround time – amount of time to execute a particular process. Waiting time – amount of time a process has been waiting in the ready queue. Response time – amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment).
  7. What is the state of the processor, when a process is waiting for some event to occur? - Waiting state
  8. What is the important aspect of a real-time system or Mission Critical Systems? - A real time operating system has well defined fixed time constraints. Process must be done within the defined constraints or the system will fail. An example is the operating system for a flight control computer or an advanced jet airplane. Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Real-Time systems may be either hard or soft real-time. Hard real-time: Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM), Conflicts with time-sharing systems, not supported by general-purpose operating systems. Soft real-time: Limited utility in industrial control of robotics, Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.
  9. What is the difference between Hard and Soft real-time systems? - A hard real-time system guarantees that critical tasks complete on time. This goal requires that all delays in the system be bounded from the retrieval of the stored data to the time that it takes the operating system to finish any request made of it. A soft real time system where a critical real-time task gets priority over other tasks and retains that priority until it completes. As in hard real time systems kernel delays need to be bounded
  10. What is the cause of thrashing? How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem? - Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault. The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming. It can be eliminated by reducing the level of multiprogramming.
  11. What is multi tasking, multi programming, multi threading? - Multi programming: Multiprogramming is the technique of running several programs at a time using timesharing. It allows a computer to do several things at the same time. Multiprogramming creates logical parallelism. The concept of multiprogramming is that the operating system keeps several jobs in memory simultaneously. The operating system selects a job from the job pool and starts executing a job, when that job needs to wait for any i/o operations the CPU is switched to another job. So the main idea here is that the CPU is never idle. Multi tasking: Multitasking is the logical extension of multiprogramming .The concept of multitasking is quite similar to multiprogramming but difference is that the switching between jobs occurs so frequently that the users can interact with each program while it is running. This concept is also known as time-sharing systems. A time-shared operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of time-shared system. Multi threading: An application typically is implemented as a separate process with several threads of control. In some situations a single application may be required to perform several similar tasks for example a web server accepts client requests for web pages, images, sound, and so forth. A busy web server may have several of clients concurrently accessing it. If the web server ran as a traditional single-threaded process, it would be able to service only one client at a time. The amount of time that a client might have to wait for its request to be serviced could be enormous. So it is efficient to have one process that contains multiple threads to serve the same purpose. This approach would multithread the web-server process, the server would create a separate thread that would listen for client requests when a request was made rather than creating another process it would create another thread to service the request. To get the advantages like responsiveness, Resource sharing economy and utilization of multiprocessor architectures multithreading concept can be used.
  12. What is hard disk and what is its purpose? - Hard disk is the secondary storage device, which holds the data in bulk, and it holds the data on the magnetic medium of the disk.Hard disks have a hard platter that holds the magnetic medium, the magnetic medium can be easily erased and rewritten, and a typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files.
  13. What is fragmentation? Different types of fragmentation? - Fragmentation occurs in a dynamic memory allocation system when many of the free blocks are too small to satisfy any request. External Fragmentation: External Fragmentation happens when a dynamic memory allocation algorithm allocates some memory and a small piece is left over that cannot be effectively used. If too much external fragmentation occurs, the amount of usable memory is drastically reduced. Total memory space exists to satisfy a request, but it is not contiguous. Internal Fragmentation: Internal fragmentation is the space wasted inside of allocated memory blocks because of restriction on the allowed sizes of allocated blocks. Allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used
  14. What is DRAM? In which form does it store data? - DRAM is not the best, but it’s cheap, does the job, and is available almost everywhere you look. DRAM data resides in a cell made of a capacitor and a transistor. The capacitor tends to lose data unless it’s recharged every couple of milliseconds, and this recharging tends to slow down the performance of DRAM compared to speedier RAM types.
  15. What is Dispatcher? - Dispatcher module gives control of the CPU to the process selected by the short-term scheduler; this involves: Switching context, Switching to user mode, Jumping to the proper location in the user program to restart that program, dispatch latency – time it takes for the dispatcher to stop one process and start another running.
  16. What is CPU Scheduler? - Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. CPU scheduling decisions may take place when a process: 1.Switches from running to waiting state. 2.Switches from running to ready state. 3.Switches from waiting to ready. 4.Terminates. Scheduling under 1 and 4 is non-preemptive. All other scheduling is preemptive.
  17. What is Context Switch? - Switching the CPU to another process requires saving the state of the old process and loading the saved state for the new process. This task is known as a context switch. Context-switch time is pure overhead, because the system does no useful work while switching. Its speed varies from machine to machine, depending on the memory speed, the number of registers which must be copied, the existed of special instructions(such as a single instruction to load or store all registers).
  18. What is cache memory? - Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory.
  19. What is a Safe State and what is its use in deadlock avoidance? - When a process requests an available resource, system must decide if immediate allocation leaves the system in a safe state. System is in safe state if there exists a safe sequence of all processes. Deadlock Avoidance: ensure that a system will never enter an unsafe state.
  20. What is a Real-Time System? - A real time process is a process that must respond to the events within a certain time period. A real time operating system is an operating system that can run real time processes successfully

Windows admin interview questions

  1. Describe how the DHCP lease is obtained. It’s a four-step process consisting of (a) IP request, (b) IP offer, © IP selection and (d) acknowledgement.
  2. I can’t seem to access the Internet, don’t have any access to the corporate network and on ipconfig my address is 169.254.*.*. What happened? The 169.254.*.* netmask is assigned to Windows machines running 98/2000/XP if the DHCP server is not available. The name for the technology is APIPA (Automatic Private Internet Protocol Addressing).
  3. We’ve installed a new Windows-based DHCP server, however, the users do not seem to be getting DHCP leases off of it. The server must be authorized first with the Active Directory.
  4. How can you force the client to give up the dhcp lease if you have access to the client PC? ipconfig /release
  5. What authentication options do Windows 2000 Servers have for remote clients? PAP, SPAP, CHAP, MS-CHAP and EAP.
  6. What are the networking protocol options for the Windows clients if for some reason you do not want to use TCP/IP? NWLink (Novell), NetBEUI, AppleTalk (Apple).
  7. What is data link layer in the OSI reference model responsible for? Data link layer is located above the physical layer, but below the network layer. Taking raw data bits and packaging them into frames. The network layer will be responsible for addressing the frames, while the physical layer is responsible for retrieving and sending raw data bits.
  8. What is binding order? The order by which the network protocols are used for client-server communications. The most frequently used protocols should be at the top.
  9. How do cryptography-based keys ensure the validity of data transferred across the network? Each IP packet is assigned a checksum, so if the checksums do not match on both receiving and transmitting ends, the data was modified or corrupted.
  10. Should we deploy IPSEC-based security or certificate-based security? They are really two different technologies. IPSec secures the TCP/IP communication and protects the integrity of the packets. Certificate-based security ensures the validity of authenticated clients and servers.
  11. What is LMHOSTS file? It’s a file stored on a host machine that is used to resolve NetBIOS to specific IP addresses.
  12. What’s the difference between forward lookup and reverse lookup in DNS? Forward lookup is name-to-address, the reverse lookup is address-to-name.
  13. How can you recover a file encrypted using EFS? Use the domain recovery agent.