A Technical I.T./DevOps Blog
Problem scenario
You run Java programs on your Linux server. You want to view content of Java thread dumps. What should you do?
Solution
Prerequisites
Install Java if it has not already been installed. See this posting if you need assistance.
You may or may not want to learn more about what a Java thread is;
…
Problem scenario
You run a Cargo command, but you get this:
error: no such command `add`
Did you mean `b`?
What should you do?
Solution
Run this: sudo cargo install cargo-edit
It can take 15 minutes to run. This should eliminate the problem.
…
Continue reading “How Do You Troubleshoot the Cargo Problem “error: no such subcommand: add”?”
Problem scenario
How do you write a Python 3 program to parse the text of a web page and determine if a string is on the web page or not?
Solution
Change the “yoururl” variable assignment and the “searchterm” assignment below to what you desire. Then run the program below:
import re
import requests
yoururl = ‘https://www.continualintegration.com/’
searchterm = “learned”
r = requests.get(yoururl)
found = re.search(searchterm, …
Continue reading “How Do You Get Python to Search a Web Page for a Specific Pattern?”
Problem scenario
You need to write a Python program to see if a list of unique integers is in order. You can copy the list and sort it to compare the ideal state to the list provided. The program must print out a relevant message if a swap of two numbers can place those two numbers in the correct order. The program must print out if a given number is already in order.
…
Continue reading “How Do You Write a Python Program to Test if Integers Are in Order?”
Problem scenario
You have Nginx configured. The access logs never pick up any POST message content. You get 405 error messages. What do you do?
Solution
This will send a message payload — but not via POST. It may not work for your situation. To get a message to be sent to a website (a listening web service), craft a URL that does not necessarily exist,
…
Continue reading “How Do You Configure Nginx to Listen to Messages Sent via HTTP?”
Problem scenario
You run kubectl describe pods. You see a message in the output that says
networkPlugin cni failed to set up pod network: open /run/flannel/subnet.env: no such file or directory.
How do you fix this?
Possible Solution #1
Log into every worker node. Make sure it has /run/flannel/subnet.env with the following four lines:
FLANNEL_NETWORK=10.244.0.0/16
FLANNEL_SUBNET=10.244.0.1/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=true
(This solution was adapted from https://www.programmersought.com/article/7824768991/)
Possible Solution #2
Run this: kubectl get pods.
…
Problem scenario
You run a Vagrant command. But you get this message: “/usr/share/rubygems/rubygems/core_ext/kernel_require.rb:83:in `require’: cannot load such file — winrm-elevated (LoadError)”
What should you do?
Solution
Run this command:
vagrant plugin install winrm-elevated …
Problem scenario
You have read about level-trigger and edge-trigger notification mechanisms in Linux. Why are they called level-trigger and edge-trigger? Where do they get their names?
Answer
Electronics and processing electric signals. Edges represent changes to a state. A level state represents the lack of a change. Here is a diagram:
This answer was adapted from the following postings:
https://hackernoon.com/photos/QdWX77c6s5Skk99abuNLlG6AEZZ2-9w23y8s
http://venkateshabbarapu.blogspot.com/2013/03/edge-triggered-vs-level-triggered.html
FFR
Notification mechanisms are components of input and output in Linux.
…
Continue reading “What Is The Etymology of the Terms Level-Trigger and Edge-Trigger?”
Problem scenario
You want to write a basic program in Rust to know you have it installed correctly. What do you do?
Solution
sudo curl –proto ‘=https’ –tlsv1.2 -sSf https://sh.rustup.rs | sh
2. Create a file called contint.rs with the following four lines:
// We recommend calling this contint.rs
fn main() {
println!(“Hello World!”); …
Continue reading “How Do You Write a “Hello World” Command in Rust?”
Problem scenario
You see Python code with this “-str” syntax. What does it do?
Answer
It is purely for readability. To help your coworkers we recommend using the “-str” syntax if a function returns a string. Otherwise the way to find out is to read the code or temporarily change the code and use type(variable_returned) to show the data type of that which is/was returned.
…
Continue reading “What Does the “-> str” Syntax Signify in Python Functions?”