How Do You Install Splunk in a Docker Container?

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Problem scenario
You want to run Splunk from a Docker container. What do you do?

Solution
Prerequisites
Install Docker. If you need assistance, see this posting.

Procedures
1. Run this command: docker pull splunk/splunk:latest

2. Run this command, but replace “simpleword” with the password that you want the administrator account for the web UI to have:

docker run -d -p 8000:8000 -e ‘SPLUNK_START_ARGS=–accept-license’ -e ‘SPLUNK_PASSWORD=simpleword’ splunk/splunk:latest

3.

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How Do You Set up Nginx as an HTTP Load Balancer for Other Instances of Nginx Running in Docker?

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Problem scenario
You have many Docker containers running Nginx.  You want to leverage these instances for users to go to one web site and then be automatically routed to different underlying Nginx instances in Docker containers.  How do you create a single website for web clients to go to with a reverse proxy balancing the load behind-the-scenes?

Solution
Overview
We accomplish an example with four Docker containers each using a free version of Nginx. 

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How Do You Set up Nginx as an HTTP Load Balancer So Client Requests (from Web Browsers) Go to Certain Nginx Servers More Frequently Than Others?

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Problem scenario
You have certain Nginx servers with ample resources whereas others have minimal resources.  Based on geographic locations and data center bandwidth locations and costs, you want to assign fractions of the web traffic from client workstations (requests from web browsers) to different Nginx servers more than others.  You do not want round-robin, equal distribution of traffic.  You want customized HTTP load balancing in accord with unequal configurations.  How do you distribute this traffic proportionately according to your desired specifications?

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Where Is The “Welcome to Nginx!” Page Stored in a Docker Container?

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Problem scenario
You installed Nginx in a Docker container on a RedHat Linux server.  You go to this container with a web browser and see the default screen.  Where is the default file (on the back-end) that users see from the front-end by default that says “Welcome to nginx!”?

Solution
This is the name and location of the file (assuming the Docker container was created via the public repository):

/usr/share/nginx/html/index.html

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How Do You Troubleshoot a Docker Container Supporting a Web Service That Web Browsers Cannot Seem to Reach?

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Problem scenario
You have configured a Docker container with a web service (e.g., Apache web server or Nginx).  You configured the listening, external port to be 80 or a different port number.  You find the web server (either Apache or Nginx) is not working from a web browser.  How do you find what is wrong?

Solution
#1  Use nmap to test the port and IP address. 

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What is a Container Breakout?

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Question
What is a container breakout?

Answer
A container breakout is an the act of a user or process in a container gaining access to its underlying host server. Containerization is the isolation of processes and/or disk space on a server. A container is isolated from the host server via cgroups and namespaces. Bypassing the cgroup(s) and namespace(s) through intentional acts can be desirable for legitimate systems engineers.

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How Do You Determine the IP Address Assignments of Running Docker Containers?

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Problem scenario
You created some Docker containers and assigned them IP addresses. How do you find out what their IP addresses are?

Solution

1. Run this command: docker ps -a # find the container ID of the container you want to know about
2. Run this command but substitute “container_id” with the container ID you found above:
docker inspect -f ‘{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}’ container_id

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Why Would a MongoDB Container Work on an Ubuntu Host but Not a SUSE Host?

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Problem scenario
You have two Linux servers in AWS, and each one has the same flavor (i.e., same amount of RAM and same number of processors). One is Ubuntu and another is SUSE. These commands will create working containers in Ubuntu:

docker run –name name1-mongo -d mongo
docker run –name name2-mongo -d mongo:2

This command will not create a working container in SUSE:

docker run –name name2-mongo -d mongo:2

The container that is created will never start.

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How Do You Set up Nginx as an HTTP Load Balancer So Client Requests (from Web Browsers) Do Not Go to Certain Nginx Servers unless Others Are Down?

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Problem scenario
You have a web server running Nginx that acts as a reverse proxy server.  On occasion your regular web (Nginx) servers go down.  You want to have one or two web (Nginx) servers that are  reserved as backups exclusively.  You do not want traffic going to these servers unless the main Nginx servers are unavailable (either due to network or server failure).  You can allocate RAM and CPU to these reserved servers on demand. 

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How Do You Troubleshoot the Error “Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock”?

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Problem scenario
You try to run a Docker command, but you get this error: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.29/containers/json?all=1: dial unix /var/run/docker.sock: connect: permission denied

What should you do?

Solution
Have you added the user who was trying to execute the command to the “docker” group?

This command would add the user jdoe to the “docker” group:
sudo usermod -aG docker jdoe

If you ran the above command as the jdoe user,

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