Understanding the OSI model and its layers

The OSI model is the part of the Open Systems Interconnection project at the International Organisation for Standardisation.

The OSI model characterizes and provides a standard set of protocols for communication functions of a telecommunication or network system regardless to its underlying architecture.

It provides interoperability and helps in easy troubleshooting of the network.
The OSI model is not a protocol, it is a network architecture that is flexible, robust and inter-operable.

It is divided into seven different layers:

  • Physical Layer
  • Data link Layer
  • Network Layer
  • Transport Layer
  • Session Layer
  • Presentation Layer
  • Application Layer

Lets look into each layer one by one,

Layer 7: Application layer

  • The application layer is the layer close to the user, which means both the application layer and the user interact with the software application.
  • It acts as a interface between application and user.
  • Application-layer functions include identifying communication partners, determining resource availability, and synchronising communication.

Layer 6: Presentation layer

  • The presentation layer handles the delivery and formatting of information. this layer presents data for the application or the network.
  • It converts data into the standard format.
  • It performs functions such as encryption, decryption, data compression, data decompression and character encoding.
  • Protocols used are eXternal Data Representation (XDR), Network Data Representation (NDR), X.25 Packet Assembler/Dis-assembler Protocol (PAD), Lightweight Presentation Protocol (LPP), Internet key exchange (IKE)

Layer 5: Session layer

  • Its main function is to manage communication sessions – continuous exchange of information.
  • It provides the mechanism for opening, closing and managing a session between end-user application processes.
  • It creates a session ID for each application and keeps the data separate for each.
  • In case of a connection loss this protocol will try to recover the connection.
  • If a connection is not used for a long duration, then session-layer protocol will close or re-open it.
  • It provides either full duplex or half-duplex operation and provides synchronisation points in the messages exchanged.
  • Protocols used are ADSP, ASP, H.245, ISO-SP, iSNS, L2F, L2TP, NetBIOS, PAP, PPTP, RPC, RTCP, SMPP, SCP, SOCKS, ZIP, SDP, SIP.

Layer 4: Transport layer

  • Transport layer provides functions and procedures for transferring data to the destination.
  • Its the bridge between hardware and software layer. The heart of the OSI layer.
  • The transport layer controls link through flow control, segmentation/de-segmentation, and error control.
  • This layer can keep track of the segments and re-transmit those that fail delivery.
  • The transport layer also provides the acknowledgement signal on successful transmission of data and sends the next data if no errors occurred.
  • It creates segments of the data dividing them into smaller layer.
  • Responsible for process to process delivery.
  • Protocols used are TCP and UDP.

Layer 3: Network Layer

  • The Network layer is responsible for the delivery of individual packets from the source host to destination.
  • It is used to communicate between different network.
  • This layer uses logical addressing (adds IP address in the header).
  • It decides the path in which the information must flow.
  • The main functions are Routing and forwarding data, logical addressing, error detection, sequencing of data and flow control.
  • Data is in the form of packets.
  • Protocols used are RIP, OSPF, BGP, EIGRP, Apple Talk
  • Devices: Router, Firewalls, L3 switch

Layer 2: DataLink Layer

  • This layer is responsible for moving frames from one node to another.
  • It is responsible for communication with the Local Area Network.
  • Data shared is in the form of Frames.
  • Responsibility of this layer are framing, physical addressing, flow control, error control, access control.
  • Physical addressing – also called as MAC addressing or Layer 2 addressing.
  • It is divided into two sublayers : Logical Link Control (LLC) and Media Access Control (MAC).
  • MAC address is a 48 bit hexadecimal address.
  • Protocols used are ARP, RARP, ICMP, IGMP, HDLC, PPP.
  • Devices: NIC, Switch, Bridge.

Layer 1: Physical layer

  • The Physical layer is responsible for movement of individual bits from one hop to another.
  • It coordinates the function required to carry a bit stream over a physical medium.
  • Main functions are modification of data into digital signals, establish and termination of connection, effectively share resources among multiple users.
  • Devices: NIC, HUB, Repeaters and Modem.

Remembering the OSI Model 7 layers – 8 mnemonic tricks:

From Application to Physical:

All People Seem To Need Data Processing
All Pros Search Top Notch Donut Places
A Penguin Said That Nobody Drinks Pepsi
A Priest Saw Two Nuns Doing Pushups

From Physical to Application:

Please Do Not Throw Sausage Pizza Away
Pew! Dead Ninja Turtles Smell Particularly Awful
People Don’t Need To See Paula Abdul
Pete Doesn’t Need To Sell Pickles Anymore

Password-protect your MS-Word document

Microsoft Word utility is a commonly used application and many time you feel the need to Password-protect your MS-Word document . Sometimes, we wish only a selected group of people to have access to the data in our Word documents.

Password-protect your MS-Word documentThe MS-Word in Office 365 gives you several tools to encrypt and Password-protect your MS-Word document . Here is how you can do it:

Step-1: Open the document you want to protect in MS Word.
Step-2: Click on ‘File’ and go to Info, click on ‘Protect Document’ next.
Step-3: Now, click on ‘Encrypt with Password’ option.
Step-4: The ‘Encrypt Document’ window will open next; you’ve to give a password for the document. The password is case-sensitive. After creating the password, click ‘OK’.
Step-5: Type the password again for the confirmation. Click ‘OK’.
Step-6: Save the document again and close it.
Step-7: Open the document again. Now, to access the document, you will have to use the password. Type in password and  click ‘OK’ to open the document.

If you want to remove the password, here are the steps:

Step-1: Click on ‘File’ and then click on ‘Protect Document’.
Step-2: Click on ‘Encrypt with Password’. At the next window, delete the dots that are hiding your password and then click ‘OK’.
Step-3: Save the document again and close it. When you open it the next time, you don’t have to enter the password and you can access it directly.

Note: The password that you use should ideally be complex and yet easy to remember. Because if you happen to forget it, there is no way you can retrieve or reset it, and hence, you will lose access to your own document. So, make sure that the password you give is easy to memorize. You can even write it down somewhere. This will help in case you forget it in the future.

Display is not working on the monitor. How to fix it?

Display is not working

There are times when you turn on the system and you find out that the display is not working, not only screen but also the mind goes blank! Not anymore, This post has tips you can follow to figure out the problem and think of solution.

If the problem is not blank screen but a blue screen with errors, refer to the post about blue screen of death and how to troubleshoot it.


display is not working

Monitor is off

Well, make sure the monitor is turned on. Check the LED. If no light comes on after several attempts, proceed to the next section.

Computer in sleep mode

If you went away from the computer for sometime and returned to a black screen, it is likely that the computer is asleep. Move the mouse, press buttons or any key. If none of those actions work, press the power button.

Loose connections

Check the data cable

Make sure that your monitor’s data transfer cable is properly connected to the computer. It should be firmly in place. Most new displays uses a DVI or HDMI cable and port.

Check the power cable

Ensure the monitor is getting power by verifying that is a light (blue, green, or orange) on the front or bottom of the monitor’s panel.

When you see no lights on the monitor, make sure it is connected to a working wall outlet. If the power cord is removable from the back of the monitor, replace it with another power cable. If you still cannot turn on the monitor after trying another wall outlet and cable, the monitor is broken and should be replaced.

Check  LED status

If the monitor status light (mostly located on the bottom of the monitor’s bezel) is orange or flashing, the monitor might be in a suspend mode, to come out of it move the mouse or press a key on the keyboard. If this does not help, reconnect the data cable to the computer and back of the monitor, and then restart your computer.

Try with different cable

If your monitor is getting power, but you don’t see an image, the data cable may be the issue. Try another DVI, HDMI, or VGA cable with your monitor.

Turn up the brightness and contrast

When you’re able to view your monitor’s settings menu even though the screen is blank, maybe  you need to increase the brightness and contrast.

Failed POST

If the computer doesn’t pass Power On Self Test, it won’t turn on and your monitor will remain black. If you hear beep sounds when you turn on your computer, run through the POST troubleshooting steps to find out the problem.

Hardware Problem

If you have followed the tips above and still have the same issue, your computer may have either a improper monitor, video card, or motherboard. The best method of determining this is to try the suggestions below.

Get someone else’s computer a computer monitor and connect it to your computer

If another monitor works on your computer, it means your monitor is bad and that might be the reason display is not working. While it may be possible to have the monitor serviced, it is often cheaper and easier to purchase a new one.

Connect your monitor to the other computer

If your monitor works on the other computer, the chances are that your video card is bad. Remove video card from the affected computer and install it in another computer. If it does not work in the other computer, the video card is probably not working and needs to be replaced.

If your monitor and video card works with another computer, your motherboard probably has an issue. You can attempt to troubleshoot motherboard problems. If you find out the motherboard is bad, or you are unable to successfully run diagnostic tests, motherboard replacement might be needed.

Filter spam and annoying calls on android phones

filter spam and annoying calls

You’re in the middle of something important or just hanging out with friends and a spam call has buzzed on your smartphone.  We’ve all been there and it can be pretty annoying. Google has now come with a feature in its Phone app which will at least warn you about these irritating calls. So here are a few steps that you need to follow to turn on this option on your Android smartphone:

Steps to Filter spam and annoying calls

Step 1: Open the default Phone app on your smartphone
Step 2: Tap on the three dots toggle on the right hand side
Step 3: Click on More
Step 4: You’ll need to click on the Settings option
Step 5: Now, here you will see the Caller ID & Spam option. Turn it off/on depending on the setting active on your phone.

Here it’s important to know that the caller ID and Spam option is by default on. In case it’s off, just turn it on.

There is another option available on the Phone app to filter spam and annoying calls. You need to follow the following steps to do so:

Step 1: Open the Phone app on your phone
Step 2: Go to Recent Calls

Step 3: Select a call from the list you want to mark as Spam

Step 4: After that, tap on the Block/report Spam option

Step 5: The app will ask you to check if you want to block the number

Step 6: If you do get the option, then you can also choose Report call as spam

Step 7: If that option isn’t available, then you can simply choose to block a particular number which is making those irritating calls.


Note: You will need a smartphone that is running Android 6.0 or above.

While the calls might not stop totally, at least they will bother you less.

Tips for buying laptop

buying laptop

Things to check out while buying laptop

When purchasing a computer, it is likely that you are going to have a general idea of what you may like in the computer or how you would like to configure the computer. Below is a listing of the various components likely to be found in a computer, and recommendations and tips for components

Battery usage

Determine how long the battery is expected to last under normal use. Many manufacturers will indicate a battery usage time but this may be at the lowest possible settings; ensure that the manufacturer clarifies what the standard battery usage life is when using the portable computer in all power modes.


All portable computers come with a display. While it is almost always possible to hook up an external monitor when traveling with the laptop, the display is an important consideration. When looking at the display, ensure it is large enough for your needs. If you want to reduce the cost , go for smaller screens, unless price is an important consideration we highly suggest that you purchase a laptop with at least a 12″ or larger LCD and recommend an LCD size of 14″.


Drives are can be an important consideration, overlooked sometimes though. Portable computers can come with various drive configurations, for example:

  • One drive bay where the CD-ROM and the Floppy drive are interchangeable. For users who utilize the floppy drive often, this may be an issue; however, for other users who do not utilize the floppy, this actually makes the computer lighter and thinner with one drive bay.
  • Two drive bay portable computers have a floppy solution as well as CD-ROM solutions. These computers will be a less expensive computer when compared to the other solutions; however, it adds on the weight to computer.
  • No drive bay portable computers allow for a laptop to be extremely light and utilize external drives instead of internal.  while it may appear to be a portable solution, many manufacturers will charge you an additional price for the external drives, which will eventually be needed.
Hard drive

Hard drives have and always will be an important consideration to think about when purchasing a new portable computer. Like a standard computer, the hard drive will be the destination of all your files and information, and if that drive is to become full, that drive must be replaced or another external drive needs to be added to the computer. When looking at the space of the hard drive, always get the maximum size hard drive, considering you will always have plenty of files to store.


Does the portable computer include any locking system? If yes, what locking system is included? This can be important for users who are on the move .


Memory is and has always been an important consideration when buying laptop. Determine the amount of memory included in the computer as well as verify if that memory can be upgraded in the future. The more memory the computer has, the more efficient the computer is.


If you need a modem, ensure that a modem is included with the portable computer. In addition, verify if the modem is an internal or PC-CARD (PCMCIA) modem as you may require all the available PC-CARD slots in the future. PC-CARD modems are type II.

Network Card

Ensure that a network card is included with the portable computer. In addition, verify if the network card is an internal or PC-CARD (PCMCIA) network card as you may need the available PC-CARD slots in the future. Network PC-CARDs are type II that for most computers allows for an additional type II to be connected.


The computer processor is and will always be an important consideration when purchasing a computer. Today, with multiple CPU/Processor manufacturers, it may be more confusing as well as more cost efficient to look at the different processors available. Compare the different processors in line with your requirements and go for the best one while buying laptop.

Sound card

Sound cards are important, however, the majority of all computer users will find that most standard sound cards will suit their needs. However, some users may enjoy purchasing more advanced sounds cards that will increase the amount of speakers that can be used and in some games and programs and the sound quality.

When looking at the sound aspect of a portable computer, many laptops do not have sufficient sound and will require external speakers or headphones. Ensure that the sound quality meets your needs.


Weight is another important consideration when buying laptop as the computer will be carried; the lighter the portable computer, the more easy it will be to carry.

Video card

Video cards are becoming an extremely important factor when buying laptop. While this may surprise some, a video card can make or break a computer when it comes to playing games. Most games today require additional video memory as well as special video modes. With a video card with little video memory or without these modes, the computer will be unable to play these games. In addition, the advances in video cards can dramatically increase the user enjoyment of the game being played.


When looking at purchasing any brand of portable computer you will hear good and bad feedback. Regardless if the feedback is good or bad, these stories are always based on the experience of that user. While it may be true that the user had a bad or terrible experience with that computer, all computer manufacturers have had users who have had a bad experience and there is no such thing as a bad or perfect computer manufacturer.


Free add-ons? Some computer companies may entice you into purchasing a computer by giving you free add-ons. These add-ons may be advertised as free, however, ensure or ask if the add-on price is not just being added to the overall computer price.

Unless you have done your research on the additional add-on, do not consider the add-on. While in some cases it may be beneficial to get a printer, scanner, camera or PC Cards with a computer, you may be paying premium for the additional add-on, or in the case of the printer, you may have to pay premium on the ink in the future. Do you research, ensure that if you get an additional hardware or add-ons that the hardware will suit your needs and that it does not end up being something that is not going to be used.


While most manufacturers today are reducing the documentation included with their computers, it is still a good idea to find out what documentation if any is included with the computer.

All computer manufacturers will include some paper documentation; however, does this information include documentation about upgrading the computer in the future? How to connect the cables to the computer? Documentation on how to use the software such as the additional included software?

Note: It is important to distinguish between paper documentation and on-line documentation. On-line documentation, which is being found more today, is information that is either locally on the computer or can be accessed via the Internet. If the information is available over the Internet, see how that information looks and if it suits your needs before purchasing the computer.


We use location to describe different cases. First, what is the location of where the computer is purchased: If the computer is purchased at a local retail store, can the computer be returned to that store if unsatisfactory? If the computer is purchased through mail order or directly through the computer manufacturer or reseller, where can the computer be returned if unsatisfactory?

Second, can the shop location of where the computer was purchased service the computer? If not where is the closest location to where the computer can be serviced?

Third, if the computer is purchased directly from the computer manufacturer and is shipped through mail, how is it shipped? What is the time period for the computer to arrive to your destination? What happens if the computer is damaged during shipping?


Refurbished is a term used to describe a computer or a hardware device or component in a computer that has been used; however, it has been looked at and determined to be in working order. However, because the product has been used or purchased, it cannot be sold as new.

Refurbished computers have a lower price and are a good deal for users looking for a better deal. However, compare the price of the refurbished computer to a new computer and the number of years it has been used.


Service is an important consideration to look at when you are buying laptop, new or used. The service is how many companies describe the repair of a computer if it or a component within it is to become broken. Below is a listing of recommended services.

  1. Is the service onsite, meaning a technician will come to your location to replace or fix a bad component. If the service is onsite, is it for the complete time of the warranty?
  2. If onsite is not offered, what is and for how long?
  3. Can the computer be taken to a local service center? If yes, what is the closest authorized service center?
  4. What is the time frame the service takes to occur? For example, if the computer has a bad component, what is the time it takes for a technician to come onsite and replace that component, or what is the time it takes to have the computer sent in to be fixed? Finally, if that time frame is not accomplished, what is the company willing to do? Would they be willing to provide you with a loaned computer?
  5. Because the computer is a portable computer, is International Service available? This allows users who may be in a different country to have their computer fixed in that country.

Software, for many computer users especially new users, is thought to be an important consideration when buying laptop. Granted there is software that we highly recommend looking for when purchasing a computer, such as word processor or spread sheet program, some computer companies may over hype the software package. Below is a listing of what to look for when looking at the software included with the laptop.

  1. Does the software include Microsoft Office or Corel Suite? These packages allow you to have a word processor and a spread sheet. For the majority of all users, this should be an important consideration.
  2. Is the software full versions of the software or is the software demo programs or shareware programs?

Things to consider when looking at the support options of a computer are mentioned below.

  1. Is support open 24 hours, 7 days a week? If not, what are the hours?
  2. Is support open on holidays? If not, what days are it closed?
  3. What support options are available? Phone? E-mail? Web? Chat?

While this option may not be considered at first when purchasing a laptop computer, it is an important consideration. Below is a listing of different options to look for when looking to upgrade a portable computer.

  1. What can be upgraded in the computer? RAM? CPU? Hard Drive? If available to upgrade, what are the maximum amounts or is it specified within documentation provided with the computer?
  2. Whether the upgrades are something that the end-user can do or does it require a service center to install?

Finally, what warranty is offered by the computer manufacturer? How long is the warranty? Does the warranty cover both hardware and software issues?

Warranty can cause frustrations for most users. A warranty of at least 1 year is highly recommended. Many cheap computers only come with a 90 day warranty; meaning if a part goes bad, you pay for the part as well as the service. This may not be an issue for users who just need a cheap computer and are willing to replace parts and service the computer.



Be careful for the below scams and tricks when buying a laptop computer.

Get what you pay for

Make sure you are paying for what you get. It has been known that computer companies may list a processor being a specific speed but may actually have a different speed into the computer. This, unfortunately, can be very easy as any user can ‘over clock’ a processor, making it appear as one speed but in reality being a completely different speed. For example, you may buy a 733MHz processor but instead get a 500MHz.

To determine the processor speed, open the computer and look at the processor itself( this might be difficult though). Do not look at the processor through a software program or through BIOS as these values can be changed or tricked.


Legal software

When purchasing a computer, ensure it comes with legal software. Many end-users or small computer companies who build or sell computers may provide you illegal copies of software. Verify that the software that came with your computer is on a standard CD and not a burnt CD. A burnt or home-made CD will be a different looking CD and have a gold or green bottom. Make sure that if the software requires a license or registration number that it was included with the computer. An example of software that includes these certificates is Microsoft Office and Windows.

Story of internet – The Network of Networks

A journey into story of internet

Everyone of us use Internet… But do you know how it originated and transformed to what it is today???

Here you go… Lets have a peek into the Bygone times,

Around 1960’s, the theories related to the internet started. In July 1961, Leonard Kleinrock at MIT published the first paper on packet switching theory. In August 1962, the articles written by J.C.R. Licklider of MIT stated Galactic network concept (the first noted description of interactions through network) – Concept similar to todays internet.

Later in October 1962, Licklider – First head of computer research program at DARPA, convinced his successors at DARPA, Ivan Sutherland, Bob Taylor, and MIT researcher Lawrence G. Roberts, of the importance of this networking concept.

In 1964, Leonard Kleinrock published a book on packet switching theory. Kleinrock convinced Roberts of the theoretical feasibility of communications using packets rather than circuits, which was a major step towards the developement of the computer networking.

In 1965, Roberts connected the TX-2 computer in Mass to the Q-32 in California with a low speed dial-up telephonic line building the first ever wide-area computer network (However small). But using circuit switching!!!.. which was inadequate for the job. Finally he agreed on Leonard Kleinrock on packet switching.

Later Roberts joined DARPA in 1966. In 1967, He suggested the plan of ARPANET and presented paper in a conference where he got some more info regarding the researches going on parallely in other organisations. August 1968, DARPA structured ARPANET and the key component was IMPs (Interface message processors)

In 1969, UCLA (Kleinrock’s laboratory where he developed packet switching theory) was selected as a first node of the ARPANET, therefore the first host computer was connected. One month later, SRI (Stanford Research Institute) became the second node (due to the project on Augmentation of Human Intellect carried out at SRI).

First host to host message was sent from UCLA to SRI.

Later two more nodes were added at the end of 1969, network creation started!

In 1970, initial ARPANET host to host protocal was release by S. Crocker, it was called as Network Control Protocol(NCP). The first international public demonstration of the ARPANET was held at ICCC – International Computer Conference in 1972 (In the same year Email concept was introduced).

The typical ARPANET grew into an internet. It was based on the idea that there would be multiple independent networks connected to other forming the internetworking architeture. For these different networks to communicate an open architecture was required. But the NCP had no ability to address different networking concept, It had a limitation that all the networks had to be build in a similar manner. The assumption was that the ARPANET cannot be changed.

This was a major draw back as it had no error control and any devition from the traditinal ARPANET would not work.

In later stages two organizations, International Organization for Standardization (ISO) and International Telegraph and Telephone Consultative Committee (CCITT) defined similar kind of networking model which supported the open architecture concept, these concepts put together formed the OSI Reference model. A turning point in the story of the internet. Having this as a reference different network can be created independently and could communicate which each other. The internetworking was finally possible.

Meanwhile Kahn from DARPA also devloped a similar model to OSI called te TCP/IP model. This new protocol was more over a communication protocol were as NCP just acted like a device driver.

Initially the internet was used only in defence and TOP 20 organizations.A major motivation for both the ARPANET and the Internet was the resource sharing. However, while file transfer and remote login (Telnet) were very important applications, electronic mail probably had the most significant impact of the innovations from that era.

When desktop computers first appeared, it was thought by some that TCP was too complex to run on a personal computer. David Clark and his research group at MIT explained that a simple implementation of TCP was possible. They demostrated an implementation, first for the Xerox Alto and then for the IBM PC. That implementation confirmed the interoperable with other TCPs and showed that workstations as well as large time-sharing systems could be a part of the Internet.

The development of Local area networks, PCs and workstations in the 1980s allowed the Internet to flourish at a greater extent. Ethernet technology, developed by Bob Metcalfe at Xerox PARC in 1973, is now probably the dominant network technology in the Internet. Having many networks has resulted in a number of new concepts and changes to the underlying network technology. First, it resulted into classification of networks inorder accommodate the range of networks into Class A, Class B and Class C.

Later to make it easy for people to use the network, hosts were assigned names, so that it was not necessary to remember the numeric addresses. Originally, there were a very few limited number of hosts, so it was easy to maintain a single table of all the hosts and their associated names and addresses. But as the network grew into having a large number of independently managed networks, having a single table of hosts was no longer making sense, and the Domain Name System (DNS) was invented by Paul Mockapetris of USC/ISI.

The increase in te size of network also challenged the router capability, to overcome this the hierarchical model of routing was replaced with IGP – Interior Gateway protocol and EGP – Exterior gateway protocol. Thus, by 1986, Internet was well established as a technology supporting the community of researchers and developers and was beginning to be used by other communities for daily computer network communications. Hence stared the cyber era.

Right now 80% of the people in the world use internet.

As the network grew larger many researches are carried on, new protocols and technologies evolve along with the threats as well. Thereby increasing the need for the network security.


File operations in linux using simple commands

Once you are equipped with the basic commands in linux, the next step will be learning file operations in linux using commands. For a primer on basic commands check linux basic commands.

Have you ever tried to copy,paste,move or remove the files in your linux system using commands? Tough eh? Not really!

file operations in linux

Lets begin with the commands on how to create files and directories.




*Creating empty file

# touch file1

This command creates an empty file file1

*creating a file with text content

# cat > file1
…input line1
…input line 2

To save the file press CTRL+D

*View the file content

# cat file1

Opens the file and shows the contents

*Append (add lines to the bottom) the file with more number of input lines

# cat >> file1
…new input line

Save with CTRL +D

*Creating a directory

# mkdir dir1

The above command creates a directory dir1 . Let me remind you a directory is similar to the folder.

*Creating multiple directories in a single line of command

# mkdir dir1 dir2 dir3

It will create three directories dir1 dir2 and dir3

Note: While creating a directory which has space between the names, use double quote(” “). For example, “my directory”.

*Copying the file

# cp file1 dir1

The command above will copy and paste the file1 into directory dir1.
If you copy a file to another regular file, it will overwrite to the destination file.

*Copying a directory

# cp -r dir1 dir2

The option ‘-r’ is used to copy the directory along with its contents and subdirectories.

*Moving a file or directory

# mv file1 dir1
# mv dir1 dir2

Its similar to cut and paste operation.

Note: Renaming a file is similar to moving the old file to a new file with different name in same location.

*Deleting a file

# rm file1

use the option “-f” to force delete.

*Deleting a directory

#rm -r dir1
#rm  -rf  dir1 ( to force delete)

Linux basic commands for Beginners-Part 2

Welcome to the next part of linux basic commands.

In case you have missed the previous post, or need a quick review on where we started, here is the link.

Continuing from the last post in Basic linux commands series, I am going to mention the most commonly used commands by a Linux BEGINNER.

linux basic commands

Changing the hostname

#hostnamectl  set-hostname  yourhostname.domain

The hostname can be with or without domain name.

Checking OS details


In systems based on redhat , this command will show you the OS, kernel, vendor details.

Configuring date and time


This command shows you the date and time currently in your OS.


It provides more details on the timezone and the NTP status.

#timedatectl set-time 12:00

the above command will change the time to 12 o clock.

#timedatectl  set-time  2018-07-01 

This changes the date to 7th of july 2018.

Note that the command to change date and time is same. And the syntax for date and time should be strictly followed to avoid the errors.

Kernel details

#uname  -r

Shows the kernel name.

#uname  -a

Shows kernel name, version, architecture and other details.

Current directory name


Prints the current working directory on screen. In other words shows your current location in directory hierarchy.


#shutdown -h 12:00

The system will shutdown at 12’o clock.

#shutdown -h now

The system will shutdown instantly.

Power off and reboot


powers off the OS.


reboots the system.

You may wonder what is the difference between “shutdown and poweroff”, the first one is a systematic process whereas the later powers off the OS without closing any running programs or saving changes.

Other useful Linux basic commands


Shows the name of user logged in that terminal first.


Shows last successful login attempts of all user accounts.


Gives the list of accounts which failed the login.


displays the name of current terminal.

#su username

switches to the user account mentioned in place of “username”.


These linux basic commands are good to start with , if you further want to explore then you can use this site link.

Blue screen errors in windows and how to fix it.

There are multiple types of blue screen or blue screen of death errors in a Microsoft windows based OS. Before fixing it, it is neccessary that you should know the types.

If you get only blue screen without the error codes, probably the problem is with video card or the monitor. Check your video card and monitor in this case.

If you are getting a blue screen and then your computer suddenly reboots without being able to read the text in the blue screen, follow the steps below. when you are unable to get into Windows to perform the steps below, boot the computer into Safe Mode.

If you are unable to boot into Safe Mode, you may have corrupt Windows system files, a defective memory chip or a damaged hard drive. You should run hardware diagnostic tests to determine if the memory or hard drive is causing the blue screen errors.

**right-click on My Computer or Computer, from the start menu or desktop.
**Click the Properties option.
**In the System Properties window, click the Advanced tab.
**On the Advanced tab, go to Startup and Recovery section and click the Settings button.
**In the Startup and Recovery window, uncheck the Automatically restart check box.
**Click OK.

Blue screen errors

Windows NT, 2000, XP, Vista, and later versions of Windows have a blue screen error that is similar to the example shown below. These error messages often contain more detailed information and will contain information that you can search and find. If you’re not getting a blue screen error that looks like the example below, refer the fatal exception error troubleshooting.


blue screen error

Locate the line containing all “capital letters with underscores” instead of spaces, such as the above example, BAD_POOL_HEADER. Write this information down. If you do not see anything written in all caps with underscores like this, skip this step.
Get either the STOP: error message at the top of the error, or in the “Technical Information:” portion of the error. For example, in the above error, it is STOP: 0x00000019, write the first portion of this error message down.
Finally, if technical information is shown, write down the file and the address.

Once you have the above information, you can start troubleshooting the issue.

For information on slow running computers refer this link.

PC shortcut keys

PC Shortcut keys provide an easier to navigate through the computer and open launch applications quickly. Shortcut keys are generally accessed by using the Alt key , Command key (on Apple computers), Ctrl key, or Shift key in conmbination with another key. Commonly listing a shortcut is listing the modifier key(alt,shift or ctrl), a plus symbol, and another key. In other words, “Ctrl+S” is telling you to press and hold the Ctrl key, and then press the S key too.

PC shortcut keys
Common PC shortcut keys

Below is a list of some of the most commonly used basic shortcut keys that work with almost every computer and software programs. It is highly advised that all users keep a good note of these shortcut keys or try to memorize them. It will highly increase your productivity.

Tip: Some special characters are also located on the number keys (below the F1 – F12 keys). You can enter these special characters by pressing the Shift key and the number key that has the special character mentioned on it.

Shortcut Keys     Description

Alt+F                File menu options in current program.
Alt+E               Edit options in current program
Alt+Tab          Switch between open programs
F1                    Universal Help in almost every Windows program.
F2                   Rename a selected file
F5                   Refresh the current program window
Ctrl+N          Create a new or blank document in some software programs.
Ctrl+O          Open a file in current software program
Ctrl+A           Select all text.
Ctrl+B          Change selected text to be Bold
Ctrl+I           Change selected text to be in Italics
Ctrl+U          Change selected text to be Underlined
Ctrl+F          Open find window for current document or window.
Ctrl+S          Save current document file.
Ctrl+X         Cut selected item.
Shift+Del    Cut selected item.
Ctrl+C         Copy selected item.
Ctrl+Ins      Copy selected item
Ctrl+V         Paste
Shift+Ins    Paste
Ctrl+Y         Redo last action
Ctrl+Z         Undo last action
Ctrl+K         Insert hyperlink for selected text
Ctrl+P         Print the current page or document.
Home          Goes to beginning of current line.
Ctrl+Home Goes to beginning of document.
End              Goes to end of current line.
Ctrl+End    Goes to end of document.
Shift+Home Highlights from current position to beginning of line.
Shift+End     Highlights from current position to end of line.
Ctrl+Left-arrow   Moves one word to the left at a time.
Ctrl+Right-arrow  Moves one word to the right at a time.
Ctrl+Esc        Opens the START menu
Ctrl+Shift+Esc Opens Windows Task Manager
Alt+F4           Close the currently active program
Alt+Enter      Open the Properties for the selected item (file, folder, shortcut, etc.)


This list of PC shortcut keys will save you a lot of time. For Troubleshooting the PC speed issues visit this link.