RAID stands for what?

RAID stands for what?

• Redundant Array of Independent Disks
• Redundantly Available Inline Disk
• Robust Advanced Inventory Diagram
• Random Access Inline Disks 

EXPLANATION

 

RAID (Redundant Array of Inexpensive Disks^[1] or Drives, or Redundant Array of Independent Disks) is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. This was in contrast to the previous concept of highly reliable mainframe disk drives referred to as "single large expensive disk" (SLED).^[2][3]
Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy and performance. The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1. Each scheme, or RAID level, provides a different balance among the key goals: reliability, availability, performance, and capacity. RAID levels greater than RAID 0 provide protection against unrecoverable sector read errors, as well as against failures of whole physical drives.

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What is the variable symbol in PHP programming?

What is the variable symbol in PHP programming?

• ?
• %
• $
• @ 

EXPLANATION

The leading $ symbol before a variable name is called a sigil. Its purpose is to make it clear that the name following the sigil is a variable and not something else, like a function name or a constant or a keyword. Sigils remove ambiguity to make the programming language interpreter's job easier.

Many other programming languages use the $ sigil in similar ways, to denote a variable that holds a single string.

• Perl dates back to 1987.
• Shell scripting languages date back to 1979.
• BASIC dates back to 1964.

So the answer of why PHP uses $ is:

1. For practical reasons because the language needs some way to distinguish variables from other syntax elements like functions, constants, and keywords.
2. Because it’s traditional and familiar to many programmers to use $ as a sigil for variables.

 

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What DNS record type is used to look up an email server using an email's domain name?

What DNS record type is used to look up an email server using an email's domain name?

• PTR
• MX
• A
• SRV 

EXPLANATION

Mail Exchange (MX) records are DNS records that are necessary for delivering email to your address.
In simple DNS terms, an MX record is used to tell the world which mail servers accept incoming mail for your domain and where emails sent to your domain should be routed to. If your MX records are not pointed to the correct location, you will not receive email.

How to use Nslookup to verify MX record configuration

1. Go to Start > Run and type cmd .
2. At a command prompt, type nslookup , and then press Enter.
3. Type server <IP address> ;,where IP address is the IP address of your external DNS server.
4. Type set q=M X, and then press Enter.
5. Type <domain name> , where domain name is the name of your domain, and then press Enter.

 

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What is end-to-end delay?

What is end-to-end delay?

• Packet travel time from source to destination
• The wait time for a pay check
• Time taken for ISP to bring a link up
• The delay during a VoIP call 

EXPLANATION

End-to-end delay or one-way delay (OWD) refers to the time taken for a packet to be transmitted across a network from source to destination. It is a common term in IP network monitoring, and differs from round-trip time (RTT) in that only path in the one direction from source to destination is measured.

Measurement

The ping utility measures the RTT, that is, the time to go and come back to a host. Half the RTT is often used as an approximation of OWD but this assumes that the forward and back paths are the same in terms of congestion, number of hops, or quality of service (QoS). This is not always a good assumption. To avoid such problems, the OWD may be measured directly.
OWDs may be measured between two points A and B of an IP network through the use of synchronized clocks; A records a timestamp on the packet and sends it to B, which notes the receiving time and calculates the OWD as their difference. The transmitted packets need to be identified at source and destination in order to avoid packet loss or packet reordering. However, this method suffers several limitations, such as requiring intensive cooperation between both parties, and the accuracy of the measured delay is subject to the synchronization precision.
The Minimum-Pairs Protocol is an example by which several cooperating entities, A, B, and C, could measure OWDs between one of them and a fourth less cooperative one (e.g., between B and X).^[1]

Delay components

End-to-end-delay in networks comes from several sources including transmission delay, propagation delay, processing delay and queuing delay.

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This virus activated every Friday the 13th, affects both .EXE and .COM files and deletes any programs run on that day. What is the name of that virus?

This virus activated every Friday the 13th, affects both .EXE and .COM files and deletes any programs run on that day. What is the name of that virus?

• I Love You
• Solar Sunrise
• Chernobyl
• Jerusalem

EXPLANATION

On a day like today, we remember one of the viruses that has caused the most headaches for users: Friday the 13 th.

The virus Jerusalem, also known as Friday the 13^th, was created in Israel in 1988 to celebrate the 40^th anniversary of the creation of the Jewish state.
To activate the virus, the calendar only had to hit Friday the 13^th and all the programs and files that were being used would be infected and eliminated.
There wasn’t a specific method to spread the virus, but that it was done through normal systems like floppies, CD-ROM or attachments in emails.

How It Works?

–  Infects files with extensions of COM, EXE or SYS and increases in size whenever the file is executed
–  It reduces the memory available on the computer
–  Causes your computer system to slow down
–  Every the Friday the 13th the virus is activated, and eliminates computer files that are used that day

 

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The following Linux command was run with an exit status of zero: " find /home/terry -name "*".txt -name "*".text " What is the command's output?

The following Linux command was run with an exit status of zero: " find /home/terry -name "*".txt -name "*".text " What is the command's output?

• All file names that end in ".text"
• Nothing
• Two files literally named "*.txt" and "*.text"
• All file names that end in ".txt" 

 

EXPLANATION

The expression    -name "*".txt   -name "*".text   is evaluated left to right right for each name encountered as the directories are traversed.  Logical AND is the default when an operator is not specified between tests.  The asterisk is quoted, so it is not expanded by the shell when the ENTER key is pressed, but is used by "find" to match any value to the left of the period.   Each name is also evaluated for  "txt"   and  "text" to the right of the period.  Since the single name being tested cannot end in both .txt and .text, no name can be matched by the expression, and there will be no output to "find".
The following Linux command was run with an exit status of zero: " find /home/terry -name "*".txt -name "*".text " What is the command's output?

# find /home/terry -name "*".txt   -name "*".text  ##Running as root
# echo $?      ## Show the exit status of the above "find"
0

Note that the command was successful (exit status 0), even though there were no matches. An exit status of 0 means that "find" was successful in walking the directory tree.  An exit status of 0 does not mean that the expression was matched.
Using the  " -or "  operator, this "find" command will output names ending in  .txt  or  .text

# find /home/terry -name "*".txt  -or    -name "*".text
/home/terry/.local/share/contacts/WARNING_README.txt
/home/terry/tg/test.text
/home/terry/.config/libreoffice/4-suse/user/uno_packages/cache/log.txt
/home/terry/.mozilla/firefox/v0h37x7l.default/revocations.txt
/home/terry/.mozilla/firefox/v0h37x7l.default/SiteSecurityServiceState.txt
# echo $?      ## Show the exit status of the above "find"
0

Note that if the user does not have permission to traverse the directory, the exit status will indicate failure, and there won't be any hits for matching names in the directories for which access is denied to a non-root user:

$ find /home/terry -name "*".txt -o -name "*".text  2>/dev/null  ##redirecting stderr to remove clutter
/home/terry/tg/test.text
$ echo $?      ## Show the exit status of the above "find"
1

"GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known....
Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND).  Where an operator is missing, -a is assumed....
find exits with status 0 if all files are processed successfully, greater than 0 if errors occur. This is deliberately a very broad description, but if the return value is non-zero, you should not rely on the correctness of the results of find."

See also:
https://pubs.opengroup.org/onlinepubs/009695399/utilities/find.html

"EXIT STATUS
The following exit values shall be returned:
0  All path operands were traversed successfully.
>0  An error occurred."

SOURCE

http://man7.org/linux/man-pages/man1/find.1.html

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What feature in Windows alerts you when a program starts that could make changes requiring admin access?

What feature in Windows alerts you when a program starts that could make changes requiring admin access?

• SECPOL
• UAC
• GPEDIT
• MSC 

EXPLANATION

When Windows launched Vista in 2008, it brought a large list of improvements over previous versions. One of the largest selling points for Vista was the increased security that it offered and one of the central aspects of this increased security is UAC, but exactly what is UAC? Windows Vista has the built-in ability to automatically reduce the potential of security breeches in the system. It does that by automatically enabling a feature called User Account Control (UAC). The UAC forces users that are part of the local administrators group to run like they were regular users with no administrative privileges.

Whenever a user that is a member of the local administrators group (or even a member of the Domain Admins group if the computer is part of an Active Directory domain) tries to perform a task that requires administrative privileges, the operating system halts the operation and prompts the user to acknowledge it prior to running the task.

Note the little shield icon next to some of the items in the above screenshot. These items, if clicked upon, will invoke the UAC prompt, and the following message is displayed:

In case the user is not a member of the local administrators group and he or she tries to perform a task that requires such privileges, they are prompted to enter the valid credentials of an administrator (similar to the Run As command in existing Windows XP/2003):

Although UAC clearly improves the security on Windows Vista, under some scenarios you might want to disable it, for example when giving demos in front of an audience (demos that are not security related, for example). Some home users might be tempted to disable UAC because of the additional mouse clicking it brings into their system, however I urge them not to immediately do so, and try to get used to it instead

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