What is IPsec?

What is IPsec?

• A hard drive encryption tool
• A protocol for secure communication
• An encryption algorithom in networks
• An architecture or security standard 

 

EXPLANATION

n computing, Internet Protocol Security is a secure network protocol suite of IPv4 that authenticates and encrypts the packets of data sent over an IPv4 network. Because of the complexity or immaturity of the IP security protocols, the initial IPv4 was developed without or barely with security protocols such that the IP version was incomplete, open or left for further research development.

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What is the number of bits in a nibble?

What is the number of bits in a nibble?

• 8 Bits
• 4 Bits
• 6 Bits
• 2 Bits 

EXPLANATION

multiply the digital storage value by 4

Each 1 or 0 in a binary number is called a bit. From there, a group of 4 bits is called a nibble, and 8-bits makes a byte. Bytes are a pretty common buzzword when working in binary. Processors are all built to work with a set length of bits, which is usually this length is a multiple of a byte: 8, 16, 32, 64, etc.

 

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What do applications use to communicate with the kernel?

What do applications use to communicate with the kernel?

• Shells
• System calls
• Shell scripts
• C programs 

 

EXPLANATION

In computing, a system call is the programmatic way in which a computer program requests a service from the kernel of the operating system it is executed on. This may include hardware-related services, creation and execution of new processes, and communication with integral kernel services such as process scheduling. System calls provide an essential interface between a process and the operating system.

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What Linux command would you use to figure out the path of an executable file?

What Linux command would you use to figure out the path of an executable file?

• where
• what
• which
• wexec 

EXPLANATION

Find the correct path to an executable file in Unix

Several Unix dialects use the whereis command to find where programs, or executables, are stored in the file structure of the computer. To use it at the Unix prompt, enter:

  whereis command

Replace command with the name of the executable for which you are looking. For example, if you are looking for the location of the lpr command, you would enter:

  whereis lpr

The whereis command will return something like the following:

  lpr: /usr/ucb/lpr /usr/man/man1/lpr.1

In this example, the query asked about the lpr command, which spools jobs to printers. The operating system returned two answers, and thus two paths. The first path is the location of the lpr executable, and the second path is the location of the lpr manual page.
To find the path the operating system uses to execute a command when you enter it on the command line, use the which command instead, for example:

  which lpr

This command will output something like the following:

  /var/bsd/lpr

This means that when you enter lpr at the command line, the system is really executing /var/bsd/lpr.

 

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If you’re looking to find out the size of each file in a given directory, what Linux command would you use?

If you’re looking to find out the size of each file in a given directory, what Linux command would you use?

• ls -i
• du
• ls -a
• ls -la 

 

EXPLANATION

du -sh file_path
 
Detail

• du (disc usage) command estimates file_path space usage
• The options -sh are (from man du):
  

    -s, --summarize
           display only a total for each argument
  
    -h, --human-readable
           print sizes in human readable format (e.g., 1K 234M 2G)

  To check more than one directory and see the total, use du -sch:
  

    -c, --total
           produce a grand total

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