How Do You Get Passed an Error about an Environment Variable When Installing etcd on Linux?

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Problem scneario
According to Coreos.com, etcd is  “[a] distributed, reliable key-value store” to be used on  “a distributed system.”  You are trying to install etcd, but you get an error about an environment variable and invalid syntax.  

For example, you try to run this script:
./etcd

But you get this output:  

“2017-03-31 19:22:19.332257 I | flags: recognized and used environment variable ETCD_VERSION=2.2.0
2017-03-31 19:22:19.332385 C | etcdmain: invalid value “2.2.0” for ETCD_VERSION: strconv.ParseBool: parsing “2.2.0”: invalid syntax”

What should you do to install 

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How Do You Determine a MAC Address of an IoT Device (without Network Administrator Access to a Router)?

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Problem scenario
You have a device (e.g., some IoT gadget such as an EZviz camera) that can connect to a network (e.g., via WiFi).  But you do not have access to the administration (e.g., back end) of the router itself. You want to learn the IoT device’s MAC address (e.g., for a third party that can grant the device WiFi access).  If you administered the router,

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How Do You Protect Your Privacy When You Are Traveling?

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Updated on 8/1/21

Problem scenario
You want to travel and protect your privacy.  You use a cell phone, smart phone, and/or laptop like anyone else.  What can you do to enhance or preserve your privacy?
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Solution
There are three parts to this solution.  The first part involves items you would bring with you.  The second part is for items that help secure your home when you are away. 

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How Do You Check If a Variable in Ruby Is a Boolean?

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Problem scenario
You want to determine if a variable is being assigned a non-string “true” or “false” data type.  That is, you want to distinguish from a string value of true/false and the Boolean, built-in, supported data type of true/false.  Some programming languages support Boolean or bit values.  Ruby has a number of data types.  There is a feature that Ruby supports to test for most of its datatypes.  

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How Do You Troubleshoot a CentOS Server Not Being Able to Reach the Internet or outside Your Network?

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Problem scenario:  From a CentOS server, you try to ping an IP address outside of your network (e.g., 8.8.8.8).  You get “connect: Network is unreachable” as the response.  Your server has an IP address and subnet mask.  What is wrong?

Solution
1.  Ensure that the network has a default gateway.  If the network equipment that connects the server to the network has no gateway to outside the network,

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A List of Apache Spark Books

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99 Apache Spark Interview Questions for Professionals by Yogesh Kumar
Advanced Analytics with Spark: Patterns for Learning from Data at Scale by Juliet Hougland, Uri Laserson, Sean Owen, Sandy Ryza and Josh Wills
Apache Spark 2 for Beginners by Rajanarayanan Thottuvaikkatumana
Apache Spark in 24 Hours, Sams Teach Yourself by Jeffrey Aven
Apache Spark for Data Science Cookbook by Padma Priya Chitturi
Apache Spark for Java Developers by Sumit Kumar and Sourav Gulati
Apache Spark Graph Processing by Rindra Ramamonjison
Apache Spark Interview Question &

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How Do You Test If a Variable Is a String or a Numeric Data Type in Ruby?

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Problem scenario
You want to test if a given variable is a Numeric or String.  These are built-in data types that Ruby has.

What should you do?

Solution
Append “.is_a? Numeric” or “.is_a? String” to variable.  For an example, here is code that explicitly prints out if the data type is a Numeric or String.

var1 = 123
an = var1.is_a?

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nixCraft at cyberciti.biz Has a Number of Great Articles

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How Do You Configure Two Linux Guest Servers Running on Oracle VirtualBox to Have Network Connectivity with Each Other?

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Problem scenario:  On a Windows host you have Oracle VirtualBox.  You want to establish TCP/IP connectivity with the two guest CentOS Linux virtual servers.  When you try to ping one from the other, you get “destination host unreachable.”  The servers have Internet connectivity.  How do you get them to communicate with each other via a networking protocol?

Solution
On each guest server,

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