A Technical I.T./DevOps Blog
Problem scenario
When using a “docker run” command you get this error: “Error response from daemon: User specified IP address is supported on user defined networks only.” What do you do to create a user-defined network?
Solution
#1 From the Linux server (the Docker host), run this command: ip addr show
#2 Look at the results for eth0.
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Problem scenario
The conjure-up menu is not working. You run a command like “conjure-up kubernetes” and get to a prompt/screen with an orange banner at the top. The “Tab” key works. But “Enter” only works on the “Quit” button. There is no error message. How do you proceed with this conjure-up menu prompt (e.g., to deploy Kubernetes) when the only option that works is “Quit”?
Solution
Expand your Putty session so the GUI is bigger on your screen (wider and longer).
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Problem scenario
You set up a load balancing mechanism for your Nginx or Apache web server. You want to test it and set up an artificial load of traffic. You want to generate a significant amount of traffic to test the HTTP load balancing mechanism. How do you do this?
Solution
Here are three scripts that can, by themselves, download a web page 100 times when they execute.
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Continue reading “How Do You Generate a Load for Your Nginx or Apache Web Server?”
Problem scenario
You are running Ubuntu Linux in AWS. You want to monitor it with your Zabbix server. (To set up a Zabbix server in AWS, see this posting.) How do you install the Zabbix client on an Ubuntu server?
Solution
Section 1
Make sure your AWS Security group allows for inbound connections from the internal IP address of the Zabbix server on any TCP port.
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Continue reading “How Do You Install the Zabbix Client on an Ubuntu AWS Instance?”
Problem scenario
You need to learn more about Kubernetes but do not know where to start. You have roughly one hour to try to know much more about Kubernetes. What should you do?
Solution
For an introduction to Kubernetes, see these two articles from Linux.com and TechTarget.
This DigitalOcean article is a little out of date (as of 9/18/17),
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Continue reading “How Can You Learn about Kubernetes in One Hour?”
Problem scenario
You have a RedHat Linux server with only 1 vCPU and 1 GB of RAM. You want to install Zabbix Server to monitor other servers. How do you deploy Zabbix server to an AWS instance of RHEL?
Solution
1. Install the LAMP stack components by running this command:
sudo yum -y install php httpd mariadb-server
2. Install essential Zabbix components with these four commands:
sudo rpm –import http://repo.zabbix.com/RPM-GPG-KEY-ZABBIX
sudo rpm -Uv
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Continue reading “How Do You Install Zabbix Server on RHEL 7.x Running in AWS?”
Today is Constitution Day. It was the final day of what was then called The Grand Convention or The Federal Convention. We now know that almost three month convention in Philadelphia as the Constitutional Convention. The meeting place was then called the State House. This building still stands, and is now called Independence Hall. We recommend people make a trip to Independence Hall and the nearby The National Constitution Center in Philadelphia to learn more about how the Constitution was drafted,
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Problem scenario
You have set up Zabbix server (i.e., using these directions). How do you configure another RedHat Linux server in AWS to be configured with the client so the Zabbix will monitor it?
Solution
Section 1
1. Make sure your AWS Security group (that governs this AWS instance that will be a client) allows for inbound connections from the internal IP address of the Zabbix server on any TCP port.
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Continue reading “How Do You Install the Zabbix Client on a RHEL 7.x Server in AWS?”
Problem scenario
In a LAPP stack deployment, a PHP variable is displaying a value “Resource id #2” or “Resource id #3.” You are expecting a different value. The PHP variable having the problem is the result of a SQL command ran against a PostgreSQL database. What should you do?
Solution
Assuming that $var1 is displaying the undesirable “Resource id #2” or “Resource id #3”,
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Continue reading “Why Does PHP Return “Resource Id #2” Or “Resource Id #3”?”
Problem scenario
You are using RedHat Linux in AWS. You have installed Docker and have a running container. You notice that “docker attach <docker ID>” commands are hanging. What do you to get inside the container?
Solution
Use “docker ps -a” to find the Docker container’s name. Then use a modified version of this draft of a command:
docker exec -it docker-name bash
#Replace “docker-name” above with the name of the Docker container as found from a “docker ps -a“command.
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Continue reading “How Do You Troubleshoot “docker attach” Commands That Hang?”