A Technical I.T./DevOps Blog
Problem scenario
From a web browser these commands succeed (where x.x.x.x is the external IP address of the Linux VM serving the web service):
Test-NetConnection -ComputerName x.x.x.x -Port 80
Test-NetConnection -ComputerName x.x.x.x -Port 443
But when you open a web browser and go to the x.x.x.x IP address, but the page does not load. You may get an error message about it timing out or not being reached or available.
…
Problem scenario
You want to send more than one line of text as the body of an email. You want to use the command prompt of a RedHat Enterprise Linux server.
Solution
Prerequisites
You have installed mailx. If you need to do this, run this command: sudo yum -y install mailx
Procedures
1.
…
Problem scenario
You are trying to use the “yum-config-manager” command. But you get this error:
“yum-config-manager: command not found”
How do you troubleshoot this error “-bash: yum-config-manager: command not found”?
Solution
Run this command: sudo yum -y install yum-utils
…
Continue reading “How Do You Troubleshoot The Error “yum-config-manager: command not found”?”
Problem scenario
You want determine what version of Java is installed (if any). What do you do?
Solution
Open PowerShell and run this command:
(Get-WmiObject Win32_Product | Where {$_.Name -match “Java”}).Version
Alternative way without PowerShell:
1. Go to Control Panel -Uninstall a Program
2. See if Java is installed
…
Continue reading “How Do You Find the Version of Java that is Installed on Your Windows Server?”
Problem scenario
You have been given a task to automate tasks in Python. You were advised to never use “import os” in a previous position. You were told that this time speed is very important. What should you do?
Possible Solution #1
If you are doing basic file manipulations such as copying or moving files, or changing files’ permissions, you may want to looking into “import shutil”.
…
Continue reading “How Should You Automate Linux Tasks with Python 2 vs Python 3?”
Problem scenario
You want to allow for TCP/IP connectivity between two VMs running Linux in Oracle VirtualBox. What do you do?
Solution
The network settings for the VMs should be as follows:
…
Continue reading “How Do You Get Oracle VirtualBox Guest Servers to Communicate with Each Other?”
Problem scenario
You inherited a Jenkins server running on Debian or Ubuntu Linux. You want to know what version of Jenkins you have. What do you do?
Solution
Run this command: dpkg -l | grep -i jenkins | awk ‘{print $3}’
…
Continue reading “How Do You Find the Version of Jenkins That is Installed on Debian/Ubuntu Linux?”
Problem scenario
You use nmap and get this error from one server but not another:
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.05 seconds
There seems to be no intermediate firewall rule stopping one server. What should you do?
Solution
The error message suggests using “-Pn”.
…
Problem scenario
You configured Nginx on a Linux server. You want to see if there has been activity on the website (e.g., via a web browser). What log file, visible on the back-end, has records of web browsing activity?
Solution
It is often here: /var/log/nginx/access.log
For general Nginx purposes, the nginx.conf file specifies the location of the Nginx logs and the names of the log files themselves.
…
Question
What is a Continuous Application?
Answer
Databricks website says this “[w]e define a continuous application as an end-to-end application that reacts to data in real-time.”
The proper term should probably be “continual application” as there may be discrete moments where no data is coming in. Many streams can be interrupted. In fact, Structured Streaming, an aspect of Spark that is used in Databricks’ “continuous applications” is based on microbatching (according to this site).
…