A Technical I.T./DevOps Blog
Problem scenario
You are trying to send an email on a Postfix server. But you keep getting this error: “454 4.7.1 jdoe@acme.com: Relay access denied”
What should you do?
Solution
…
Problem scenario
You have Python 3 installed, but you do not have pip3 installed. One of the following also apply to your situation:
Problem scenario #1
You run an Ansible playbook. You receive the error message “Aborting, target uses selinux but python bindings (libselinux-python) aren’t installed.”
Problem scenario #2
You run an Ansible playbook. You receive the error message “module ‘selinux’ has no attribute ‘is_selinux_enabled'”.
…
Continue reading “How Do You Troubleshoot Ansible Errors about SELinux?”
Problem scenario
You have Python 2 and Python 3 installed. When you run Python 3 programs, you get an error message about selinux. The message is consistent with libselinux-python not being installed.
When you enter the Python interpreter for Python 2, you can run this command without errors: import selinux
But when you enter the Python interpreter for Python 3 (e.g., python3), you get errors when you run this command: import selinux
Security of the server is not critical,
…
Continue reading “How Do You Get the libselinux-python to Work with Python 3?”
Problem scenario
In AWS Systems Manager you run an “aws ssm” command. You get “An error occurred (InvalidInstanceId) when calling the Send Command operation.” What should you do?
Solution
Are there spaces or braces inside the double quotes? These symbols are not part of the instance ID. If you are running a script or complex command, extraneous symbols may be getting injected into your instance ID.
…
Bill Gates’ father was an attorney, and President of the Washington State Bar Association (according to this site). Bill Gates was concerned with the details of contracts in Microsoft’s early days.
I.T. Contractors need to understand American law. To learn about how the contract language works, you may want to hire an attorney. To prepare yourself beforehand, you should try to learn more. If you are an independent contractor who performs software consulting,
…
Continue reading “Considerations when Negotiating the Fine Print of an Employment Contract”
Problem scenario
You want a script to test if a file is in a specific location or not. You are using Linux. What should you do?
Solution
Use this script (but modify “/path/to/file” to be the path and name of the file you are searching for):
if [ -f “/path/to/file” ]
then
echo “file exists”
else
echo “file does not exist”
fi …
Continue reading “How Do I Write a Script to Test if a File Exists?”
Problem scenario
You run this command:
sudo /opt/maven/bin/mvn activemq-perf:broker -Durl=broker:tcp://localhost:61616
You get this result:
[INFO] Scanning for projects…
Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-metadata.xml
Downloading from central: https://repo.maven.apache.org/maven2/org/codehaus/mojo/maven-metadata.xml
Downloaded from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-metadata.xml (14 kB at 17 kB/s)
Downloaded from central: https://repo.maven.apache.org/maven2/org/codehaus/mojo/maven-metadata.xml (20 kB at 25 kB/s)
[INFO] ————————————————————————
[INFO] BUILD FAILURE
[INFO] ————————————————————————
[INFO] Total time: 1.815 s
[INFO] Finished at: 2020-04-28T15:33:05Z
[INFO] ————————————————————————
[ERROR] No plugin found for prefix ‘activemq-perf’ in the current project and in the plugin groups [org.apache.maven.plugins, …
Problem scenario
You want a non-terminating (or hanging) Linux command that never finishes to go to the background. You want to use the next command line prompt. The process starts from a command you issue at the command line. How do you do you get to the next prompt?
Solution
Craft a command like this,
…
Problem scenario
You are using WordPress to host your website. Some post previews show a hyperlink “Read more…” but others have no hyperlink. Some post previews (e.g., when you search the website for a pattern) are not updating. Older versions of the post are previewing. How do you get the “Read more…” hyperlink to show in the preview and how do you get the post to be up-to-date?
…
Continue reading “How Do You Get WordPress Preview Postings to Show “>> Read more…”?”
Problem scenario
You want to use the latest (as of 2020) Python SDK to interact with AWS. What do you do?
Prerequisite
Install pip. See this posting.
Solution
Run these commands:
sudo pip3 install boto3
sudo pip3 install –upgrade pip
…
Continue reading “How Do You Install Boto3 on Ubuntu/Debian Linux?”