How Do You Copy Files into a Docker Container from the Server’s Command Line?

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Docker is itself a dependency resolution tool.  It is a container that allows a DevOps engineer to prepare one-time an OS environment with nuanced dependencies and configurations for other packages to be installed.

Leveraging the efficiency of a configuration management tool (such as Ansible, CFEngine, Chef, Puppet, and SaltStack) can empower DevOps engineering.  It can also necessitate using duplicative deployments in different environments (development, quality assurance, staging, and production).  Having a backup plan for disaster recovery is also important. 

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OpenStack Wikipedia Article: Sahara Paragraph Updated

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I edited Wikipedia’s OpenStack Article found here.  This is the paragraph for Sahara as I found it on 4/5/16:
“Sahara aims to provide users with simple means to provision Hadoop clusters by specifying several parameters like Hadoop version, cluster topology, nodes hardware details and a few more. After a user fills all the parameters, Sahara deploys the cluster in a few minutes. Sahara also provides means to scale an already-provisioned cluster by adding and removing worker nodes on demand.”
This is what I revised it to be:
“Sahara is a component to easily and rapidly provision Hadoop clusters.

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How to Handle “Failed to connect to the Docker daemon” message in Linux

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To see if Docker has started, do this command:
ps -ef | grep -i docker
If that returns only a service for the grep itself, then Docker is not running.   Occasionally the Docker service won’t start through traditional methods.  But some users have found that this command will work reliably:
docker daemon &
The “&” allows for the next prompt to return.  This method is explicit to new users of Docker too. 

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How do you install two or more RPM packages when they depend on each other?

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Question:  How do you solve circular dependency problems when installing RPMs in RedHat Linux?
Problem Scenario:  For example, you keep trying to install different RPMs, but they always require a different installation.  By exhaustively going through the dependencies, you find a circle of dependencies.  This is sometimes called mutual recursion.

Root cause:  Human error.

Solution:  The way to resolve circular dependencies is with a yum localinstall command with a list of each of the RPM packages afterward.

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How To Potentially Solve an HTTP 403 Error on An Apache Server

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Problem scenario:  You are trying to access a file on a website.  But you get the 403 Forbidden error every time.  What are some different things to look for to fix this problem?

Solution:

If you do not have access to the back-end of the web server, try these:

  1. Clear the cache/history from your web browser.
  2. Clear the cookies from your web browser.

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OpenStack Sahara Documentation

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Some open source projects don’t always listen to contributors’ feedback.  We reported a couple errors that we found in OpenStack documentation to openstack.org.  Here are the errors we saw (as of 2/2/17):

#1  If you go to this link, you’ll find two “Storm EDP” links:
http://specs.openstack.org/openstack/sahara-specs/

One points to this link:  http://specs.openstack.org/openstack/sahara-specs/specs/liberty/storm-scaling.html

We see no reason why the title/header of this above page is “Storm EDP” and not “Storm Scaling.”  My attempt at a contribution was to not have two “Storm EDP” links in the first link of this post. 

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SaltStack Technology and Terminology

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SaltStack provides for more complex configuration management than Ansible (another Python-based) configuration management tool.  Some people have criticized Salt for having too many new vocabulary words.  Like all complex technologies, they take time getting used to.  To help learn about Salt, I thought I’d provide an overview.

An SLS file is a SaltStack State file.  This file is the basis for determining the desired configuration of the client servers that are called Salt Minions. 

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Containerization Has Its Advantages Over Virtualization

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Containers, such as Docker, communicate to each other through a shared kernel.  Guest virtual machines communicate to each other through the hypervisor or host operating system.  Containers enjoy faster communication as staying within a shared kernel allows for more rapid communication than leaving a virtual machine and going out to a hypervisor (or host operating system) to communicate with another virtual machine.  Containers allow for sequestration of processes and fewer operating systems licenses compared to having a comparable solution with virtual machines. 

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How do you use the source keyword in Puppet’s DSL (when writing a manifest)?

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When writing a Puppet manifest you can use the “content” reserved word.  You then have quotes around the actual text content of this file right in the manifest itself.  This works for a file that you want to create on a Puppet Agent server as long as the content is roughly one line of text.  But for a binary file, this will not work (as it cannot appear in the manifest).  The “source” reserved word allows you to point to a specific file on the Puppet Master server. 

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