A Technical I.T./DevOps Blog
Problem scenario
You try to connect to Puppet master from Puppet agent for the first time (to get the certificate signed). You run this command: puppet agent -t -d
But you get this error: “Error: Could not send report: SSL_connect returned=1 errno=0 state=error: certificate verify failed:”
What should you do?
Solution
Are you changing the Puppet master for the Puppet agent?
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Problem scenario
In Google Cloud Platform you have a Debian Linux server. You want to install Puppet master on it. What should you do?
Solution
Prerequisites
We suggest having at least 4.5 GB of memory. This can be from RAM or a combination of RAM and swap space. To create 4 GB of /swap/space you can see this posting as a guide,
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Continue reading “How Do You Install Puppet Master on a Debian Linux Server in GCP?”
Problem scenario
You are running Ubuntu 16.x Linux and want to install Apache Cassandra. How do you install Apache Cassandra on Linux Ubuntu Linux as a single-server configuration?
Solution
These directions will work to deploy Debian 9 Linux too. They have been tested to work in AWS and GCP.
Prerequisites
i. This solution assumes that you have installed Apache Ant and Git.
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Continue reading “How Do You Install Apache Cassandra on Ubuntu 16.04?”
Problem scenario
You want every Linux server to have 2 GB of virtual memory. You want to transfer a Bash script to each server and run it with sudoer privileges. How do you transfer a file and execute it as a sudoer user?
Solution
1. Install Ansible. If you need directions on how to do this with RHEL, see this posting. For SUSE,
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Problem scenario
You want to dedicate 2 GB of your hard drive to be virtual memory (swap space for memory-intensive applications). What should you do to script this that will work on any distribution of Linux (e.g., a RedHat derivative including CentOS/RHEL/Fedora, Debian/Ubuntu, or SUSE)?
Solution
Overview
We consider virtual memory to be a hybrid of RAM “and disk space that running processes can use.
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Problem scenario
You want to install Apache Cassandra on CentOS, RHEL, or Fedora Linux. What do you do?
Solution
These directions will deploy Apache Cassandra in a solo-server configuration. This will not create a cluster. These directions will work for a physical server, a VM, an EC-2 instance in AWS or a virtual machine in GCP.
Prerequisites
i. This assumes that you have 3 GB of memory (in combination of either RAM or virtual memory,
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Continue reading “How Do You Install Apache Cassandra on a RedHat Derivative of Linux?”
Problem scenario
You created your own Docker image. You want to upload it to a repository so it is available to other servers. You want to upload a Docker image from your server into ECR (in AWS). You do not know the name of the repository. How do you do this?
Solution
Prerequisites
a. This assumes that ECR has been set up. If you need assistance,
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Continue reading “How Do You Upload a Docker Image to Amazon Elastic Container Registry?”
Problem scenario
You run “sudo npm” or “sudo node” and you get “command not found” error messages. What should you do?
Solution
Modify the /etc/sudoers file. Find the stanza with secure_path. Append “:/usr/local/bin” (with no quotes) to the line.
Here is an example of how the stanza should look (it is often on line 80 of /etc/sudoers):
Defaults secure_path = /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin
Once the /etc/sudoers file has been saved,
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Continue reading “How Do You Use “sudo npm” or “sudo node” Commands?”
Problem scenario
You want to find out what version of sudo is on your Linux server. What do you do?
Solution
Run this command:
man sudo | grep Sudo | awk ‘{print $2}’
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Continue reading “How Do You Find What Version of sudo You Are Using?”
Problem scenario
You want to see what servers are in your HDFS cluster (e.g., the DataNodes and the NameNodes). What command can display the FQDNs of such servers?
Solution
Run this command from the NameNode:
hdfs dfsadmin -report | grep Hostname
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Continue reading “How Do You List the Hostnames of the Nodes in Your HDFS Cluster?”