A Technical I.T./DevOps Blog
Problem scenario
Recently you deployed Kubernetes to AWS using JuJu. You are now eliminating the Security Groups that it created. You cannot delete a Security Group in AWS. You get an error about the Security Group being associated with one or more network interfaces. You cannot detach the network interface. You even click the “Force detachment” and then click “Yes, Detach.” Nothing works to delete the network interface or remove the Security Group.
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Problem scenario
You want to know what version of MariaDB is installed on your Linux server. You do not have credentials to log into the SQL prompt. What OS command can you run to determine the version of MariaDB?
Solution
Run this command:
mysql -h localhost -V
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Continue reading “How Do You Find the Version of MariaDB That Is Installed on Your Linux Server?”
Problem scenario
You want to install Splunk Enterprise on your RedHat Enterprise Linux server. How do you do this?
Solution
You can get a free trial here if you input the data the Splunk company requires and can agree to the terms that they have. Use an SFTP client (e.g., WinSCP) to move it to your server.
From the Linux server run this: sudo yum -y localinstall splunk-*
Run this command: sudo /opt/splunk/bin/splunk version
Read the License Agreement.
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Continue reading “How Do You Install Splunk Enterprise on a RHEL Server?”
Updated on 1/6/21
Problem scenario
You want to install open source Hadoop. You may want a single-node or multi-node deployment with CentOS/RedHat/Fedora, Debian/Ubuntu, and/or SUSE Linux distributions. You want to have most of it scripted and have the same script work on any variety of Linux. How do you install Hadoop quickly with a script that works on almost any type of Linux?
Solution
1.
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Continue reading “How Do You Install Hadoop with a Script for Any Type of Linux Server?”
Problem scenario
You want to list the instrumented JVMs on your Linux OS. Therefore you want to run the command jps. What package(s) do you need to install?
Solution
For CentOS/RedHat/Fedora run this:
sudo yum -y install java-1.8.0-openjdk-devel
For Linux SUSE run this:
sudo zypper -n install java-1_8_0-openjdk-devel
For Ubuntu/Debian Linux run this:
sudo apt-get -y install openjdk-8-jdk-headless default-jre
If you want to learn more about the Java process status tool,
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Problem scenario
You have heard about different operating system events being classified in different levels. Lesser events can be captured with logging is verbose. Major events can render a system useless. You know system logging is normally done in a file called /var/log/syslog. How do you find out which levels there are from most significant to least significant?
Solution
Use this command: man syslog
Search for the word “level” by typing this: /level <press enter>
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Continue reading “How Do You Find the Different Logging Levels of the /var/log/syslog?”
Problem scenario
When a command stops, it returns an exit code. You want to learn more about exit codes starting with the variable that stores the most recently completed Linux command’s exit code. Every time you use $? in Linux, you get 0. Why is this?
Solution
There are four links that can help you learn more. Two are from The Linux Documentation Project (one here and another here).
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Continue reading “How Do You Find the Most Recent Exit Code in Linux?”
Problem scenario
You are trying to run an s3cmd command (e.g., s3cmd ls), but it is not working. You run an s3cmd command and you get this:
ERROR: /home/jdoe/.s3cfg: None
ERROR: Configuration file not available.
ERROR: Consider using –configure parameter to create one.
What do you do?
Possible Solution #1
1. sudo find / -name .s3cfg
2.
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Continue reading “How Do You Troubleshoot an s3cmd Error About “.s3cfg: None”?”
Note: This posting should help you troubleshoot many different network problems (not just those described in the problem scenario below). Possible solutions 1 through 5 are ideal for erratic nmap results (inconsistent or discrepant output).
Problem scenario
A port seems blocked on a Linux server given the results of nmap. The host appears to be down. You know this port is not blocked by intermediate routers and/or firewalls.
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Continue reading “How Do You Troubleshoot a Network Problem?”
Happy New Years!
In Scotland New Year’s Eve is called “Hogmanay.” In other countries outside the U.S. it is called “Old Year’s Day” or “Saint Sylvester’s Day.” In America New Year’s Eve is celebrated with a variety of different traditions. Many states have their own unique traditions of dropping or lowering of different objects (e.g., a large ball in Times Square in New York City).
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Continue reading “New Year’s Eve in America and around the World”