What is the command in Unix or Linux to terminate processes without having to log out or reboot (i.e., restart) the computer?

What is the command in Unix or Linux to terminate processes without having to log out or reboot (i.e., restart) the computer?

• stop
• quit or q
• kill
• taskkill 

 

EXPLANATION

In Unix and Unix-like operating systems, kill is a command used to send a signal to a process. By default, the message sent is the termination signal, which requests that the process exit. But kill is something of a misnomer; the signal sent may have nothing to do with process killing.

SOURCE

https://en.wikipedia.org/wiki/Kill_(command)

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What does GUID refer to?

What does GUID refer to?

• Globally Unique Identifier
• Geographical User Information Database
• Global User Identifier
• Graphical User Interface Display 

EXPLANATION

Globally Unique Identifier, a unique 128-bit number that is produced by the Windows OS or by some Windows applications to identify a particular component, application, file, database entry, and/or user. For instance, a Web site may generate a GUID and assign it to a user's browser to record and track the session. A GUID is also used in a Windows registry to identify COM DLLs. Knowing where to look in the registry and having the correct GUID yields a lot information about a COM object (i.e., information in the type library, its physical location, etc.). Windows also identifies user accounts by a username (computer/domain and username) and assigns it a GUID. Some database administrators even will use GUIDs as primary key values in databases.

GUIDs can be created in a number of ways, but usually they are a combination of a few unique settings based on specific point in time (e.g., an IP address, network MAC address, clock date/time, etc.).

 

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What is the Microsoft release version of Windows 7?

What is the Microsoft release version of Windows 7?

• 7.0
• 6.2
• 6.0
• 6.1 

EXPLANATION

Reference Table for Windows Version Numbers
Operating System	Version Details	Version Number
Windows 10	Windows 10 (1903)	10.0.18362
	Windows 10 (1809)	10.0.17763
	Windows 10 (1803)	10.0.17134
	Windows 10 (1709)	10.0.16299
	Windows 10 (1703)	10.0.15063
	Windows 10 (1607)	10.0.14393
	Windows 10 (1511)	10.0.10586
	Windows 10	10.0.10240
Windows 8	Windows 8.1 (Update 1)	6.3.9600
	Windows 8.1	6.3.9200
	Windows 8	6.2.9200
Windows 7	Windows 7 SP1	6.1.7601
	Windows 7	6.1.7600
Windows Vista	Windows Vista SP2	6.0.6002
	Windows Vista SP1	6.0.6001
	Windows Vista	6.0.6000
Windows XP	Windows XP2	5.1.26003

 

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Which protocol is used to prevent switching and routing loops in networks?

Which protocol is used to prevent switching and routing loops in networks?

• Spanning Tree Protocol (STP)
• Point-to-Point Tunneling Protocol (PPTP)
• Dynamic Trunking Protocol (DTP)
• Point-to-Point Protocol (PPP) 

EXPLANATION

What is Spanning Tree?

The Spanning Tree protocol is a networking standard, as defined by the IEEE in the 802.1d standard.  The purpose of Spanning Tree is to prevent loops in the LAN and to select the fastest network links, if there are redundant links in the network.  In the event that a link in the network goes down, Spanning Tree will failover to the alternate link, if one exists.

If this sounds like what a routing protocol does then you are on the right track. Routing protocols help devices route between WAN networks (prevent loops, use alternate paths, etc) at Layer 3.  Spanning Tree could be termed a Layer 2 routing protocol for a LAN because it performs the same functions but for an Ethernet network, regardless of IP addresses.  So, Spanning Tree is not an IP routing protocol but has some similar functions for the data-link layer (Layer 2).

How Spanning Tree works

Spanning Tree works by first using an algorithm to find redundant links in the LAN and selecting the best paths. Its initial goal is to put all links in either Forwarding or Blocking. In the end, the links without a redundant link and the best links with a redundant link would be in forwarding state. The redundant links that weren’t as good as the selected links would be in blocking state.

Spanning Tree cannot use multiple links to the same destination. There is no load-sharing feature with Spanning Tree. Any redundant link that is not as preferred is blocked (essentially shut down) until the primary link goes down.

Because Spanning Tree is a complex protocol, this article won’t cover every possible feature. We will, however, give you a solid overview of the protocol and its process.

The three criteria Spanning Tree uses to decide if an interface should be in forwarding state are:

• All interfaces on the root bridge are put in forwarding state.
• For other bridges that are not the root bridge, the port that is closest to the root bridge is put in forwarding state.
• The bridge with the lowest administrative distance to the root bridge is called the designated bridge. The Ethernet interface on the designated bridge is called the designated port. That port is put into forwarding state.

But how is the root bridge elected? The root bridge is elected based on bridge ID (usually the MAC address) and a priority. By default, all priorities are the same so, by default, the switch with the lowest MAC address will become the root bridge.

How is the lowest administrative cost to the root bridge calculated? This is based on the speed of the links across the LAN, to get to that root bridge. STP uses default port costs to calculate this. These port costs can be overridden by an administrator. Here are the default STP port costs:

• 10Mb link – Cost is 100
• 100Mb link – Cost is 19
• 1Gb link – Cost is 4
• 10Gb link – Cost is 2

The costs shown are revised costs from the original STP default port costs. The IEEE did not anticipate the massive increase in speed now offered by Ethernet. Because of this 1Gb and 10Gb links could not be accommodated by the old default costs and the costs had to be revised.

How does STP prevent loops?

Because the “best ports” are put into forwarding state and the other ports are put into blocking state, there are no loops in the network. When a new switch is introduced to the network, the algorithm and port states are recalculated to prevent a new loop.

What happens when a link goes down?

Switches communicate with a BPDU (bridge protocol data unit) every 2 seconds. If the remote switch doesn’t respond, it is assumed that that switch (and its links) are down and the Spanning Tree algorithm is recalculated.

What are the STP port states?

Whenever a new port is enabled, Spanning Tree goes through the following port states to get that port to be either forwarding or blocking. They are:

• Blocking – does not forward any frames but still receives BPDU’s from other switches
• Listening – same as blocking but it is beginning its transition to forwarding frames. Unlike Blocking, in Listening mode, the port will send BPDU’s. 
• Learning – the second state in the transition to frame forwarding. In this state, the switch receives MAC address information from devices on this switch port.
• Forwarding – transmits and receives frames. This is the normal state for a port.
• Or, Disabled – the disabled state means that the switch port is administratively disabled.

 

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On a desktop or laptop what does a G3 power state refer to?

On a desktop or laptop what does a G3 power state refer to?

• Mechanical Off
• BIOS Update In Progress
• Low Power Mode For Battery Performance
• Working Off 

 

EXPLANATION

"Mechanical Off" - G3 - The system is completely off and consumes no power. The system returns to the working state only after a full reboot.
Can be performed by holding down Shift when clicking Shutdown.

SOURCE

https://docs.microsoft.com/en-us/windows/desktop/power/system-power-states

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In T-SQL, very rarely would you need to use the following:

In T-SQL, very rarely would you need to use the following:

• RIGHT JOIN
• CTE
• CURSOR
• LEFT JOIN 

EXPLANATION

Specifies a temporary named result set, known as a common table expression (CTE). This is derived from a simple query and defined within the execution scope of a single SELECT, INSERT, UPDATE, DELETE or MERGE statement. This clause can also be used in a CREATE VIEW statement as part of its defining SELECT statement. A common table expression can include references to itself. This is referred to as a recursive common table expression.

Transact-SQL Syntax Conventions

Syntax

[ WITH <common_table_expression> [ ,...n ] ]  
  
<common_table_expression>::=  
    expression_name [ ( column_name [ ,...n ] ) ]  
    AS  
    ( CTE_query_definition ) 

T-SQL stands for Transact-SQL, and is Sybase & Microsoft’s proprietary extension.

T-SQL is a programming language and very similar to PL/SQL (in Oracle), one can create T-SQL units such as SQL Scripts, Stored Procedures, Functions, Types, Triggers, etc.

SQL DBA is entirely different track and requires different skills, and have altogether different carrier path. It deals with non-programming stuff usually, like installing SQL Server, maintaining databases, backup/restore, user security, etc, and much more stuff.

Thus you won't get more people/resources with both the skills.

For more details on T-SQL, SQL and database languages and tools check this blog post: What is SQL, PL/SQL, T-SQL and difference between them

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Which of the following is true about a message transfer agent (MTA)?

Which of the following is true about a message transfer agent (MTA)?

• Forwards incoming email to the right destination
• Uses peer-to-peer application architecture
• Implements only the server portion of SMTP
• Implements only the client portion of SMTP 

EXPLANATION

Message transfer agent within Internet message handling services, a message transfer agent or mail transfer agent or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. An MTA implements both the client and server portions of the Simple Mail Transfer Protocol.

A message transfer agent receives mail from either another MTA, a mail submission agent (MSA), or a mail user agent (MUA). The transmission details are specified by the Simple Mail Transfer Protocol (SMTP). When a recipient mailbox of a message is not hosted locally, the message is relayed, that is, forwarded to another MTA. Every time an MTA receives an email message, it adds a Received trace header field to the top of the header of the message,^[4] thereby building a sequential record of MTAs handling the message. The process of choosing a target MTA for the next hop is also described in SMTP, but can usually be overridden by configuring the MTA software with specific routes.  

An MTA works in the background, while the user usually interacts directly with a mail user agent. One may distinguish initial submission as first passing through an MSA – port 587 is used for communication between an MUA and an MSA, while port 25 is used for communication between MTAs, or from an MSA to an MTA;^[5] this distinction is first made in RFC 2476.
For recipients hosted locally, the final delivery of email to a recipient mailbox is the task of a message delivery agent (MDA). For this purpose the MTA transfers the message to the message handling service component of the message delivery agent (MDA). Upon final delivery, the Return-Path field is added to the envelope to record the return path.

 

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