A Technical I.T./DevOps Blog
Problem scenario
You want a script to install Apache Flink on any type of Linux (including CentOS/RHEL/Fedora, Debian/Ubuntu and SUSE). What should you do?
Solution
Prerequisites
When using Ubuntu/Debian or SUSE servers, 1 GB of RAM is sufficient. For CentOS/RHEL/Fedora, we recommend either more RAM or use virtual memory. To find a script that will create swap space,
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Continue reading “How Do You Install Apache Flink on Any Type of Linux?”
Problem scenario
You are running a Python program or running a command from the Python 3 interpreter. You get this error:
Traceback (most recent call last):
File “”, line 1, in
ModuleNotFoundError: No module named ‘flask’
What should you do to use Flask with Python 3?
Solution
Prerequisite
You need to have pip3 installed.
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Continue reading “How Do You Troubleshoot the Error “ModuleNotFoundError: No module named ‘flask’”?”
Problem scenario
You are trying to run a pip command. But you get “/bin/python3.7: bad interpreter: Permission denied”. What should you do about these “bad interpreter” errors in response to having run pip commands?
Solution
Use “sudo” before the pip command. It should allow you to run the pip command. You may need to be a different user or obtain sudoer rights. If you need assistance with obtaining sudoer rights,
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Problem scenario
You want to list the Route Tables in your AWS account (under VPC). You are using Python and Boto3. What should you do?
Solution
Run this program with Python 3:
import boto3
ec2 = boto3.client(‘ec2’)
rts = ec2.describe_route_tables()
print(rts) …
Continue reading “How Do You Use Python and Boto3 to List VPC Route Tables?”
Problem scenario
You try to compile a Java program with a javac command. You get this error:
special.java:39: error: cannot find symbol
symbol: class foo
location: class bar
What should you do?
Possible solution
In some cases you need a keyword “new”, but in other cases you need to not have the keyword “new”.
Are you using the word “new” to the right of an equals sign “=”?
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Continue reading “How Do You Troubleshoot the Java Compilation Error “cannot find symbol”?”
Problem scenario
You have found an AWS CLI command that shows you output consistent with the console. You run this:
aws ec2 describe-vpc-peering-connection –region us-west-2 | grep pcx-abcd1234
The results show you a peering connection called pcx-abcd1234
You run this from a Python3 interpreter prompt:
import boto3
foo = boto3.resource(‘ec2’)
foo.describe_vpc_peering.connections()
print(foo)
You then search the output for pcx-abcd1234. You do not see it.
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Continue reading “Why Would Boto3 Not Show a Peering Connection That the AWS CLI Shows?”
Problem scenario
You are now an AWS administrator for an existing company. You want to find out what the password requirements are (e.g., minimum length, maximum duration, complexity requirements etc.) for IAM users. What do you do to find the minimum length?
Solution
Log into the AWS console. Go to IAM -Account Settings.
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Continue reading “How Do You Find the Minimum Password Length in AWS?”
Problem scenario
You have read about manifests in books or articles that pertain to DevOps, but are not sure what they are. What is a manifest in the I.T. field?
Answer
Manifest: Syntactic text, usually a file with a variety of details, that is used for the purpose of convergence towards a desired state.
The definition above applies to a Puppet manifest or a Kubernetes manifest.
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Problem scenario
You used “cp -i” like this: cp -i foo bar
The command succeeded but bar does not have the contents of foo. What could be wrong?
Solution
If “bar” is the name of a pre-existing directory, a copy of “foo” is in the directory named “bar”.
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Continue reading “How Do You Troubleshoot a cp Command in Linux?”
Problem scenario
When trying to compile a Java program, you get this output:
ContInt.java:15: error: expected
System.out.println(“test”);
^
ContInt.java:15: error: illegal start of type
System.out.println(“test”);
^
What do you do?
Solution
Create a class for the System.out.println statement to be in.
Here is code that would cause the error:
import java.util.Scanner; …