In Unix systems, what are semaphores?

In Unix systems, what are semaphores?

• A technique for pipeline deletion inside processes
• A technique for coordinating or synchronizing activities
• A technique for pipeline creation inside threads
• A technique for Traffic lights management inside an operating system 

 

EXPLANATION

In programming, especially in Unix systems, semaphores are a technique for coordinating or synchronizing activities in which multiple processes compete for the same operating system resources.
A semaphore is a value in a designated place in operating system (or kernel) storage that each process can check and then change. Depending on the value that is found, the process can use the resource or will find that it is already in use and must wait for some period before trying again. Semaphores can be binary (0 or 1) or can have additional values. Typically, a process using semaphores checks the value and then, if it using the resource, changes the value to reflect this so that subsequent semaphore users will know to wait.
Semaphores are commonly use for two purposes: to share a common memory space and to share access to files. Semaphores are one of the techniques for interprocess communication (IPC). The C programming language provides a set of interfaces or "functions" for managing semaphores.

SOURCE

https://whatis.techtarget.com/definition/semaphore

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With regards to DNS, what is the difference between an A record and an AAAA record?

With regards to DNS, what is the difference between an A record and an AAAA record?

• A record holds one IP for one host and AAAA record can hold up to four IPs for one host
• A record replies to one ping and AAAA record replies to four pings.
• A record is for the A-team and AAAA record is for a squad of A-teams.
• A record holds the IPv4 address and AAAA record holds the IPv6 address 

EXPLANATION

An A and AAAA record are both primary DNS records.  They associate a host name with a specific IP address, so that when a user types in a web address, their browser knows where to go for the actual website. An A record holds the IPv4 address and an AAAA record holds the IPv6 address.
More info here - https://en.wikipedia.org/wiki/List_of_DNS_record_types

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What of the following names is a USB device that registers itself as a network adapter but is a covert systems administration and penetration testing tool?

What of the following names is a USB device that registers itself as a network adapter but is a covert systems administration and penetration testing tool?

• NET Ninja
• BeamGun
• Rubber Ducky
• LAN Turtle 

EXPLANATION

The LAN Turtle is a covert Systems Administration and Penetration Testing tool providing stealth remote access, network intelligence gathering, and man-in-the-middle monitoring capabilities.
Housed within a generic "USB Ethernet Adapter" case, the LAN Turtle’s covert appearance allows it to blend into many IT environments.
See: https://lanturtle.com/ for more information

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You only want to use on-premises servers to authenticate. You would like to allow access to cloud email accounts through a user's local credentials. Which solution should you use?

You only want to use on-premises servers to authenticate. You would like to allow access to cloud email accounts through a user's local credentials. Which solution should you use?

• Implement SaaS
• Recreate user accounts in the cloud
• Replicate local user accounts to the cloud
• Identity federation 

EXPLANATION

Identity federation uses a single identity provider to authorize user access to multiple software applications, including cloud email.
Replicating user accounts means you are NOT using the on-premises user identities as you require. SaaS provides end-user software services over the network and has nothing to do with authorization. Recreating user accounts in the cloud won't work because we need to use local user accounts for authentication.

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Which of these is NOT a card bus type?

Which of these is NOT a card bus type?

• SOX
• ISA
• AGP
• PCI 

 

EXPLANATION

CardBus is the trade name for an advanced PC Card specification. The technology is used primarily in notebook and portable computers and fits in a slot like a conventional PC card. ISA, AGP, and PCI are all card bus types.
SOX is a common abbreviation for the Sarbanes-Oxley Act, a US Federal law governing publicly traded companies.

 

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Which function key is used to check for spelling in MS Office?

Which function key is used to check for spelling in MS Office?

• Alt + F11
• F5
• Alt + F4
• F7

EXPLANATION

Function key assignments common to all Microsoft Office applications are: F7 to check spelling.



 In Microsoft PowerPoint, F5 starts the slide show.



 Alt+F11 calls the Visual Basic Editor



 Alt+F4 is used to quit the application.

 

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Which of these is not a high level Linux package manager?

Which of these is not a high level Linux package manager?

• aptitude
• yum
• zypper
• linupdate

EXPLANATION

linupdate is the false one here. The others are all legitimate Linux package managers. Even though these are package managers, they use lower level tools to actually install the packages, such as rpm or dpkg.
Overview: http://www.tecmint.com/linux-package-management/
RPM & DPKG reference: http://packman.linux.is/

 

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