Operating System

How to hide folders in windows OS

noreply@blogger.com (OS) — Wed, 20 May 2015 04:52:00 +0000

In the digital age, privacy concerns are more pressing than ever. A tutorial titled "How to hide folders" seems to provide many users with a way to protect their sensitive data. However, a closer look at these guides reveals many issues that users should avoid.

To hide a folder named- 'SD' in C drive using cmd

command: -

attrib +s +h C:\SD

To unhide

command: -

attrib -s -h C:\SD

Don't worry if you forget the name of the folder.

-->go to cmd

-->type the drive in which you want to check the folders
e.g d:

--> then type dir/a

it will show all the folders.

User should prioritize more robust methods, such as encryption and secure backup practices, to safeguard their sensitive data effectively.

How to install Oracle Java Packages in Ubuntu

noreply@blogger.com (OS) — Sat, 07 Feb 2015 05:11:00 +0000

Some web services may need the Oracle Java Runtime Environment to be installed in the system for running the services properly. If you would like to get the proprietary Oracle Java packages for your system, you can download and install them.

Following these steps:-

Press Ctrl-Alt-T to run Terminal.

Enter sudo add-apt-repository ppa:webupd8team/java to add the partner repository.

Enter sudo apt-get update to update the source list.

Enter sudo apt-get install oracle-java8-installer to download and install the Oracle Java packages.

Enter sudo java -version to check the version of the Java used in the system.

Enter sudo update-alternatives --config java to choose the default Java for use in the system when necessary.

Enter sudo add-apt-repository ppa:webupd8team/java to add the partner repository.

Enter sudo apt-get update to update the source list.

Enter sudo apt-get install oracle-java8-installer to download and install the Oracle Java packages.

Enter sudo java -version to check the version of the Java used in the system.

Enter sudo update-alternatives --config java to choose the default Java for use in the system when necessary.

Note: - The new version of Oracle Java may not allow you to run applications or services that are unsigned or self-signed. If you trust the services that you're using, you may configure the security level of JRE or add the services to the Exception Site List using the Java Control Panel.

To run it, enter /usr/bin/jcontrol in the Terminal

press Alt-F2, type jcontrol then run the Oracle Java 8 plugin control panel.

How to change wallpapers Automatically in Ubuntu

noreply@blogger.com (OS) — Fri, 06 Feb 2015 07:01:00 +0000

Manual wallpaper changing method: -

You can right click your desktop, select "Change Desktop Background" and choose any one of the wallpapers pre-installed, but you need to do it each time you want to change a wallpaper.
...........................................................................

What about changing a wallpaper automatically within a certain time interval?
Install the wallpaper changer Variety and see the magic

Press Ctrl-Alt-T to run Terminal.

  Enter sudo add-apt-repository ppa:peterlevi/ppa
   Enter sudo apt-get update
   Enter sudo apt-get install variety
   Enter sudo apt-get update
   Enter sudo apt-get install variety

"With this trick of wallpaper change, you can change wallpapers in a fixed time interval from the sources you set and run it with several other settings such as randomly applying filter effects, color etc."

UBUNTU Useful commands

noreply@blogger.com (OS) — Fri, 16 Jan 2015 06:44:00 +0000

UBUNTU Useful commands

You can use keyboard shortcuts and other command line tricks to make entering commands easier and faster. You might already know about the ‘tab’ key which completes partial commands.

Here are some other keyboard shortcuts:

Ctrl+Alt+T Open Terminal

Ctrl-a Move to the start of the line.

Ctrl-e Move to the end of the line.

Ctrl-u Delete from the cursor to the beginning of the line.

Ctrl-k Delete from the cursor to the end of the line.

Ctrl-w Delete from the cursor to the start of the word.

Ctrl+Sft+V Pastes text .

Ctrl-l Clear the screen leaving the current line at the top of the screen.

Ctrl-x Ctrl-u Undo the last changes.

Ctrl-Alt-r Undo all changes to the line.

Alt-Ctrl-e Expand command line.

Ctrl-r Incremental reverse search of history.

Alt-p Non-incremental reverse search of history.

!! Execute last command in history

!abc Execute last command in history beginning with abc

!n Execute nth command in history

^abc^efg Replace first occurrence of abc with efg in last command and

execute it

Dear Reader, if you like My Blog content, feel free to comment on our blog posts.

Installing Canon Laser Printer (LBP 2900B) in Ubuntu 12.04 LTS, 14.04 LTS

noreply@blogger.com (OS) — Wed, 07 Jan 2015 08:38:00 +0000

Dear Ubuntu Users,

Please follow the following steps for
Configuration of Canon Laser Printer (LBP 2900B)in Ubuntu 14.04

step-1 Download the printer driver from the Internet

step-2 to keep it in your download folder

step-3 to extract that folder and you will get another folder

step-4 Double click on that folder, again you will get another tow folders

step-5 you have to choose “Debian” folder and double click on that folder

step-6 you will get two files, again double click on that files one by one from down to install it

step-7 open your terminal window with “root” user

Then the following commands are followed :

1. sudo mkdir /var/ccpd

2. sudo mkfifo /var/ccpd/fifo0

3.sudo chown -R lp:lp /var/ccpd

4.sudo /usr/sbin/lpadmin -p LBP2900 -m CNCUPSLBP2900CAPTK.ppd -v ccp://localhost:59787 -E

5.sudo /usr/sbin/ccpdadmin -p LBP2900 -o /dev/usb/lp0

6.sudo service ccpd start

7.sudo service ccpd status

8. Check the printer status.
captstatusui -P LBP2900

After that resart your printer and cpu manualy, then it will be work.

How Operating Systems Work

noreply@blogger.com (OS) — Mon, 08 Dec 2014 05:42:00 +0000

When you turn on your computer, it's nice to think that you're in control. There's the trusty computer mouse, which you can move anywhere on the screen, summoning up your music library or Internet browser at the slightest whim. Although it's easy to feel like a director in front of your desktop or laptop, there's a lot going on inside, and the real man behind the curtain handling the necessary tasks is the operating system.

Absolutely Important UNIX Commands

noreply@blogger.com (Unknown) — Fri, 04 Jun 2010 08:24:00 +0000

Absolutely Important UNIX Commands

cat f List contents of file

cat f1 f2 >f3 Concatenates f1(file 1) & f2(file 2) into f3(file 3)

cd returns you to your home or main directory

cd / takes you to the root, as far up (to the left) as far as possible

cd to move down (right in the pathname) a directory

cd .. moves you up (left in pathname) a directory; likewise,

cd ../../.. :- moves you up (left in the pathname) 3 directory levels

chmod ### :- changes your protections. The order is: you|group|universe (rwxrwxrwx).
There will be either a d or - before it. If there's a d, then it's a directory. If there's not, then it's a file.
You set the protections in the order rwx (read=1, write=2, execute=4). So, to set the protections for the
directory directoryname: you rwx, group r-x, universe r--, you would enter:chmod 751 .

clear :- to clear screen

compress :-compresses the file filename and puts a .Z extension on it. To uncompress it, type uncompress

cp f1 f2 :- Copy file f1 into f2

cp -r D1D2 :- copies the directory D1 and renames it D2

^-c (ctrl-c):- to kill a running process

^-d (ctrl-d):- to close an open window

df :- gives disk usage

diff f1 f2 :- Lists file differences

dig host :- domain name, IP address, and alias information for the given host.

dosdir :- to do a "dir" (~ls in UNIX) on a DOS floppy in the disk drive
dosread to read a file from a DOS floppy to your computer account
doswrite to write a file from your computer account to a DOS floppy

du :- lists all subdirectories and their sizes (in blocks?) and total directory size (in blocks?) (takes a long time)

du -a :- lists all files and their sizes (in blocks?) in present directory and total directory size (in blocks?) (takes a long time)

du -s:- lists overall directory size (in blocks?) (long but clean)

env :- shows current environment set-up

find :- Searches the named directory and it"s sub-directories for files. Most frequently called like this:
find ./ -name "t*" -print
Which searches the current directory ( and all of its sub-directories ) for any files that begin with the letter "t" and then prints them out. If you are looking for a specific filename, then replace "t*" with "filename", and "find" will print out all incidences of this file.

finger @.:- (e.g., finger johndoe@ksu.edu fingers Johndoe at Kent State University)

ftp :- establishes an ftp link with machinename

gzip :- produces files with a .gz extension.

gunzip :- decompress files created by gzip, compress or pack.
ispell f Interactively checks the spelling of the file f, giving logical alternatives to the misspelled words. Type "?" to get help. "ispell" can be accessed from the command line, and also through emacs with M-x ispell-buffer.

kill -9 -1 :- (from a remotely logged-in site) kills all running processes (essentially forces a logout) *not to be used unless nothing else works* kill -9 process-id# - kills a running process

lpq :- shows UNIX print queue

lpr :- to print the file

lpqrm job# :- removes job from printer queue

ls :- shows listing of files in present directory

ls -a :- shows listing of all files in present directory

ls -l :- shows long listing of files in present directory

ls -la | more :-shows long listing of all files in present directory

man command :- shows help on a specific command.

mkdir :- D creates a new directory called D

more :- to view the contents of a file without making changes to it one screen at a time. Hit q to quit more.

mv f1 f2 :- Rename file f1 as f2

mv f1D :- moves the file called f1 to the directory D

nslookup host:- domain name, IP address, and alias information for the given host. e.g.,nslookup www.kent.edu gives related data for www.kent.edu

passwd:- to change your password (takes an hour or so to take effect on all machines)

ping host :- to test if the host is up and running.

pwd :- present working directory

ps :- Shows processes running

ps -flu :- Shows detailed description of processes running

pquota:- Shows printer quota

quota -v :- Shows current disk usage and limits.

rlogin :- allows you to remotely log in to another machine on which you have access privileges

rm f :- Delete (removes) the file f.

rm -i f :- To be prompted for confirmation before you remove a file f, at the UNIX prompt, type

rm dir D :- Delete (removes) the empty directory D

rm - r D :- removes the directory named D and its contents - use with caution

s f :- Alphabetically sort f.

talk :- establishes an e-tak session with user@machinename

tar :- combines multiple files into one or vice-versa

telnet :- allows you to remotely log in to another machine on which you have access privileges

uncompress :- uncompresses filename.

users :- shows who's logged in on the machine

vi :- to open the file called filename in the vi text editor

who :- Shows who is currently logged on the system.

whoami :-shows username of person logged in that window

whois domain_name :- lists the domain registration record, e.g., whois kent.edu will produce the domain record for kent.edu

* :- wild card character representing any # or characters

date :- shows the time and date

date -u :- shows greenwich mean time

. :- a short cut that stands for the location you are at in a pathway. ex. cp (file (though a pathway) (. (the location you are at)

.. :- move to parent directory from any comand ex. mv (file name) ..

pwd :- shows where you are in the pathway

? :- wild card character representing one character, can be used in succesion

~ :- abbreviation for the home file ex. ls ~ lists files in home dir w/o moving there

zip :- best compression for IBM files.

User-Level Threads implementation in user-level libraries

noreply@blogger.com (Unknown) — Mon, 31 May 2010 09:52:00 +0000

User-Level Threads

User-level threads are implemented in user-level libraries, rather than via systems calls, so thread switching does not need to call operating system and to cause interruption to the kernel. In fact, the kernel knows nothing about user-level threads and manages them as if they were single-threaded processes.

Advantages:

The most obvious advantage of this technique is that a user-level threads package can be implemented on an Operating System that does not support threads. Some other advantages are

•User-level threads do not require modification to operating systems.

•Simple Representation:
Each thread is represented simply by a PC, registers, stack and a small control block, all stored in the user process address space.

•Simple Management:

This simply means that creating a thread, switching between threads and synchronization between threads can all be done without intervention of the kernel.

•Fast and Efficient:

Thread switching is not much more expensive than a procedure call.

Disadvantages:

•There is a lack of coordination between threads and operating system kernel. Therefore, process as whole gets one time slice irrespect of whether process has one thread or 1000 threads within. It is up to each thread to relinquish control to other threads.

•User-level threads requires non-blocking systems call i.e., a multithreaded kernel. Otherwise, entire process will blocked in the kernel, even if there are runable threads left in the processes. For example, if one thread causes a page fault, the process blocks

Why threads used in designing operating systems

noreply@blogger.com (Unknown) — Mon, 31 May 2010 09:49:00 +0000

The following are some reasons why we use threads in designing operating systems.

1.A process with multiple threads makes a great server, for example, a printer server.

2.Because threads can share common data, they do not need to use inter process communication.

3.Because of their very nature, threads can take advantage of multiprocessors.

Threads are cheap in the sense that.

1.They only need a stack and storage for registers therefore, threads are cheap to create.

2.Threads use very little resources of an operating system in which they are working. That is, threads do not need new address space, global data, program code or operating system resources.

3.Context switching are fast when working with threads. The reason is that we only have to save and/or restore PC, SP and registers.
But this cheapness does not come free - the biggest drawback is that there is no protection between threads.

What is Process Control Block

noreply@blogger.com (Unknown) — Mon, 31 May 2010 08:18:00 +0000

A process in an operating system is represented by a data structure known as a process control block (PCB) or process descriptor. The PCB contains important information about the specific process including

The current state of the process i.e., whether it is ready, running, waiting, or whatever.

Unique identification of the process in order to track "which is which" information.

A pointer to parent process.

Similarly, a pointer to child process (if it exists).

The priority of process (a part of CPU scheduling information).

Pointers to locate memory of processes.

A register save area.

The processor it is running on.

The PCB is a certain store that allows the operating systems to locate key information about a process. Thus, the PCB is the data structure that defines a process to the operating systems.

Definition of Process in OS

noreply@blogger.com (Unknown) — Mon, 31 May 2010 08:12:00 +0000

Definition
The term "process" was first used by the designers of the MULTICS in 1960's. Since then, the term process, used somewhat interchangeably with 'task' or 'job'. The process has been given many definitions for instance.
• A program in Execution.
• An asynchronous activity.
• The 'animated sprit' of a procedure in execution.
• The entity to which processors are assigned.
• The 'dispatchable' unit.
and many more definitions have given. As we can see from above that there is no universally agreed upon definition, but the definition "Program in Execution" seem to be most frequently used. And this is a concept are will use in the present study of operating systems.

Now that we agreed upon the definition of process, the question is what is the relation between process and program. It is same beast with different name or when this beast is sleeping (not executing) it is called program and when it is executing becomes process. Well, to be very precise. Process is not the same as program. In the following discussion we point out some of the difference between process and program. As we have mentioned earlier.
Process is not the same as program. A process is more than a program code. A process is an 'active' entity as oppose to program which consider to be a 'passive' entity. As we all know that a program is an algorithm expressed in some suitable notation, (e.g., programming language). Being a passive, a program is only a part of process. Process, on the other hand, includes:
• Current value of Program Counter (PC)
• Contents of the processors registers
• Value of the variables
• The process stack (SP) which typically contains temporary data such as subroutine parameter, return address, and temporary variables.
• A data section that contains global variables.
A process is the unit of work in a system.
In Process model, all software on the computer is organized into a number of sequential processes. A process includes PC, registers, and variables. Conceptually, each process has its own virtual CPU. In reality, the CPU switches back and forth among processes. (The rapid switching back and forth is called multiprogramming).

Operating Systems Services

noreply@blogger.com (Unknown) — Fri, 28 May 2010 10:28:00 +0000

The following are the five services provided by an operating system to the convenience of the users.

Program Execution
The purpose of a computer system is to allow the user to execute programs. So, the operating systems provide an environment where the user can conveniently run programs. The user does not have to worry about memory allocation or multitasking or anything. These things are taken care of by the operating systems.
Running a program involves allocating and deallocating memory, CPU scheduling in case of multiprocessing. These functions cannot be given to the user-level programs. So, user-level programs cannot help the user to run programs independently without the help from operating systems.

I/O Operations

Each program requires input and produces output. This involves the use of I/O. The operating systems hides the user the details of underlying hardware for the I/O. All the user sees is that the I/O has been performed without any details. So the operating systems by providing I/O makes it convenient for the users to run programs.
For efficiently and protection users cannot control I/O so this service cannot be provided by user-level programs.

File System Manipulation

The output of a program may need to be written into new files or input taken from some files. The operating systems provide this service. The user does not have to worry about secondary storage management. User gives a command for reading or writing to a file and sees his/her task accomplished. Thus, operating systems make it easier for user programs to accomplish their task.
This service involves secondary storage management. The speed of I/O that depends on secondary storage management is critical to the speed of many programs and hence I think it is best relegated to the operating systems to manage it than giving individual users the control of it. It is not difficult for the user-level programs to provide these services but for the above-mentioned reasons it is best if this service s left with the operating system.

Communications

There are instances where processes need to communicate with each other to exchange information. It may be between processes running on the same computer or running on different computers. By providing this service the operating system relieves the user of the worry of passing messages between processes. In the event where the messages need to be passed to process on the other computers through a network it can be done by the user programs. The user program may be customized to the specifics of the hardware through which the message transits and provides the service interface to the operating system.

Error Detection

An error in one part of the system may cause malfunctioning of the complete system. To avoid such a situation the operating system constantly monitors the system to detect the errors. This relieves the user of the worry of errors propagating to various parts of the system and causing malfunctioning.
This service cannot be handled by user programs because it involves monitoring and in cases altering area of memory or deallocation of memory for a faulty process. Or maybe relinquishing the CPU of a process that goes into an infinite loop. These tasks are too critical to be handed over to the user programs. A user program if given these privileges can interfere with the correct (normal) operation of the operating systems

Command Interpreter System

noreply@blogger.com (Unknown) — Fri, 28 May 2010 10:26:00 +0000

A command interpreter is an interface of the operating system with the user. The user gives commands with are executed by operating system (usually by turning them into system calls). The main function of a command interpreter is to get and execute the next user specified command. Command-Interpreter is usually not part of the kernel, since multiple command interpreters (shell, in UNIX terminology) may be supported by an operating system, and they do not really need to run in kernel mode.

There are two main advantages to separating the command interpreter from the kernel.

1. If we want to change the way the command interpreter looks, i.e., I want to change the interface of command interpreter, I am able to do that if the command interpreter is separate from the kernel. I cannot change the code of the kernel so I cannot modify the interface.

2. If the command interpreter is a part of the kernel, it is possible for a malicious process to gain access to certain part of the kernel that it showed not have to avoid this ugly scenario it is advantageous to have the command interpreter separate from kernel.

Objectives of Operating Systems

noreply@blogger.com (Unknown) — Fri, 28 May 2010 10:19:00 +0000

Objectives of Operating Systems

Modern Operating systems generally have the following three major goals. Operating systems generally accomplish these goals by running processes in low privilege and providing service calls that invoke the operating system kernel in high-privilege state.
• To hide details of hardware by creating abstraction
An abstraction is software that hides lower level details and provides a set of higher-level functions. An operating system transforms the physical world of devices, instructions, memory, and time into a virtual world that is the result of abstractions built by the operating system. There are several reasons for abstraction.
First, the code needed to control peripheral devices is not standardized. Operating systems provide subroutines called device drivers that perform operations on behalf of programs, for example, input/output operations.
Second, the operating system introduces new functions as it abstracts the hardware. For instance, the operating system introduces file abstraction so that programs do not have to deal with disks.
Third, the operating system transforms the computer hardware into multiple virtual computers, each belonging to a different program. Each program that is running is called a process. Each process views the hardware through the lens of abstraction.
Fourth, the operating system can enforce security through abstraction.

• To allocate resources to processes (Manage resources)
An operating system controls how processes (the active agents) may access resources (passive entities).

• Provide a pleasant and effective user interface
The user interacts with the operating systems through the user interface and is usually interested in the “look and feel” of the operating system. The most important components of the user interface are the command interpreter, the file system, on-line help, and application integration. The recent trend has been toward increasingly integrated graphical user interfaces that encompass the activities of multiple processes on networks of computers.
One can view Operating Systems from two points of view: Resource manager and Extended machines. From the Resource manager point of view Operating Systems manage the different parts of the system efficiently and from extended machines point of view Operating Systems provide a virtual machine to users that is more convenient to use. Structural Operating Systems can be designed as a monolithic system, a hierarchy of layers, a virtual machine system, an exokernel, or using the client-server model. The basic concepts of Operating Systems are processes, memory management, I/O management, the file systems, and security.

What is an Operating System?

noreply@blogger.com (Unknown) — Fri, 28 May 2010 10:16:00 +0000

Definition of an operating system is “the software that controls the hardware”. However, today, due to microcode we need a better definition. We see an operating system as the programs that make the hardware useable. In brief, an operating system is the set of programs that controls a computer. Some examples of operating systems are UNIX, Mach, MS-DOS, MS-Windows, Windows/NT, Chicago, OS/2, MacOS, VMS, MVS, and VM.

Controlling the computer involves software at several levels. We will differentiate kernel services, library services, and application-level services, all of which are part of the operating system. Processes run Applications, which are linked together with libraries that perform standard services. The kernel supports the processes by providing a path to the peripheral devices. The kernel responds to service calls from the processes and interrupts from the devices. The core of the operating system is the kernel, a control program that functions in privileged state (an execution context that allows all hardware instructions to be executed), reacting to interrupts from external devices and to service requests and traps from processes. Generally, the kernel is a permanent resident of the computer. It creates and terminates processes and responds to their request for service.

Operating Systems are resource managers. The main resource is computer hardware in the form of processors, storage, input/output devices, communication devices, and data. Some of the operating system functions are: implementing the user interface, sharing hardware among users, allowing users to share data among themselves, preventing users from interfering with one another, scheduling resources among users, facilitating input/output, recovering from errors, accounting for resource usage, facilitating parallel operations, organizing data for secure and rapid access, and handling network communications