Which of the following is a valid command in Linux?

Which of the following is a valid command in Linux?

• w
• x
• t
• y

EXPLANATION

Thw w command display who is logged into the Linux and Unix-like server, and what they are doing at command execution time. The syntax is:
w
I suggest that you either read Linux w command examples page or see Linux w command man page for more information.

When you type "man {name of command}" in terminal, you most often will get info from the Linux Manual on that command (note: do not enter the brackets when typing the command). i.e - man w
NAME w - Show who is logged on and what they are doing.

SYNOPSIS w [-husfVo] [user]

DESCRIPTION
w displays information about the users currently on the machine, and their processes. The header shows, in this order, the current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.
The following entries are displayed for each user: login name, the tty name, the remote host, login time, idle time, JCPU, PCPU, and the command line of their current process.
The JCPU time is the time used by all processes attached to the tty. It does not include past background jobs, but does include currently running background jobs.

 

 

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Which network topology requires terminators?

Which network topology requires terminators?

• Mesh
• Ring
• Bus
• Star 

EXPLANATION

 

The correct answer to the question “Which Network topology requires terminators?” is letter A or bus network. Before we delve into that, it is worthy to mention that there are two kinds of topology – the logical topology which define the method used for accessing a media, and Physical topology which defines the Design of the media and includes bus, ring, star, extended star, hierarchical, and mesh network.
Now that we know the two types of topology, bus topology is considered as one of the first application types of the ethernet. It requires less cable than that of star topology, but if the main cable is down, then that just means that all network is down, as well. It also requires terminators on cable end points.

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What IP address does localhost usually resolve to?

What IP address does localhost usually resolve to?

• 127.0.0.1
• 192.0.2.0
• 127.0.0.0
• 127.255.255.255 

 

EXPLANATION

  The IP address 127.0.0.1 is a special-purpose IPv4 address called localhost or loopback address. All computers use this address as their own but it doesn't let them communicate with other devices like a real IP address does.

Your computer might have the 192.168.1.115 private IP address assigned to it so that it can communicate with a router and other networked devices. However, it still has this special 127.0.0.1 address attached to it to mean "this computer," or the one you're currently on.

The loopback address is only used by the computer you're on, and only for special circumstances. This is unlike a regular IP address that is used to transfer files to and from other networked devices.

For example, a web server running on a computer can point to 127.0.0.1 so that the pages can be run locally and tested before it's deployed.

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OSI layer 1 corresponds to the:

OSI layer 1 corresponds to the:

• Application layer
• Physical layer
• Network layer
• Data link layer 

EXPLANATION

The Physical layer is also called as the Layer 1. Here are the basic functionalities of the Physical layer:

• Responsible for electrical signals, light signal, radio signals etc.
• Hardware layer of the OSI layer
• Devices like repeater, hub, cables, ethernet work on this layer
• Protocols like RS232, ATM, FDDI, Ethernet work on this layer

 

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In the OSI model, layer 3 corresponds to:

In the OSI model, layer 3 corresponds to:

• Data link layer
• Network layer
• Physical layer
• Transport layer 

EXPLANATION

The Network layer is also called as the layer 3 of the OSI model. Here are the basic functionalities of the network layer:

• Switching and routing technologies work here
• Creates logical paths between two hosts across the world wide web called as virtual circuits
• Routes the data packet to destination
• Routing and forwarding of the data packets.
• Internetworking, error handling, congestion control and packet sequencing work at this layer
• Router works at layer three
• Different network protocols like TCP/ IP, IPX, AppleTalk work at this layer

 

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A basic network switch that provides connections between LAN clients operates at which OSI layer?

A basic network switch that provides connections between LAN clients operates at which OSI layer?

• 3rd layer
• 1st layer [Physical Layer]
• 2nd layer
• 4th layer 

EXPLANATION

Layers of OSI model:

Physical layer

The Physical layer is also called as the Layer 1. Here are the basic functionalities of the Physical layer:

• Responsible for electrical signals, light signal, radio signals etc.
• Hardware layer of the OSI layer
• Devices like repeater, hub, cables, ethernet work on this layer
• Protocols like RS232, ATM, FDDI, Ethernet work on this layer

Data Link layer

The data link layer is also called as the Layer 2 of the OSI model. Here are the basic functionalities of the data link layer:

• Responsible for encoding and decoding of the electrical signals into bits.
• Manages data errors from the physical layer
• Convers electrical signals into frames
• The data link layer is divided into two sub-layers
  • The Media Access Control (MAC) layer
  • Logical Link Control (LLC) layer.
• The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it.
• The LLC layer controls frame synchronization, flow control and error checking.
• MAC address is a part of the layer 2.
• Devices like Switch work at this layer

Network Layer

The Network layer is also called as the layer 3 of the OSI model. Here are the basic functionalities of the network layer:

• Switching and routing technologies work here
• Creates logical paths between two hosts across the world wide web called as virtual circuits
• Routes the data packet to destination
• Routing and forwarding of the data packets.
• Internetworking, error handling, congestion control and packet sequencing work at this layer
• Router works at layer three
• Different network protocols like TCP/ IP, IPX, AppleTalk work at this layer

Transport layer

The Transport  layer is also called as the layer 4 of the OSI model. Here are the basic functionalities of the Transport layer:

• Responsible for the transparent transfer of data between end systems
• Responsible for end-to-end error recovery and flow control
• Responsible for complete data transfer.
• Protocols like SPX, TCP, UDP work here

Session layer

The Session  layer is also called as the layer 5 of the OSI model. Here are the basic functionalities of the Session layer:

• Responsible for establishment, management and termination of connections between applications.
• The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end.
• It deals with session and connection coordination.
• Protocols like NFS, NetBios names, RPC, SQL work at this layer.

Presentation layer

The Presentation layer is also called as the layer 6 of the OSI model. Here are the basic functionalities of the presentation layer:

• Responsible for data representation on your screen
• Encryption and decryption of the data
• Data semantics and syntax
• Layer 6 Presentation examples include encryption, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, MIDI.

Application Layer

The Application layer is also called as the layer 7 of the OSI model. Here are the basic functionalities of the Application layer:

• Application layer supports application, apps, and end-user processes.
• Quality of service
• This layer is responsible for application services for file transfers, e-mail, and other network software services.
• Protocols like Telnet, FTP, HTTP work on this layer.

 

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You want to combine four 1TB hard drives into a single array with at least 2TB of storage. Which of the below configurations gives you the best balance of performance and redundancy?

You want to combine four 1TB hard drives into a single array with at least 2TB of storage. Which of the below configurations gives you the best balance of performance and redundancy?

• RAID 6
• RAID 10
• JBOD
• RAID 5 

EXPLANATION

All of the above possible configurations provide the minimum storage requirement. Some configurations provide more storage than others, but this is not a requirement.
JBOD offers no redundancy or performance gains, but provides the most storage space of the options provided.
RAID 5 offers 3x read speed and no write performance gains. RAID 5 is fault tolerant to 1 disk, regardless of the number of

SOURCE

https://en.wikipedia.org/wiki/RAID

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