A Technical I.T./DevOps Blog
Problem scenario
You have a Git repository on one server. You want to clone it to another server. When you try to clone it, you are prompted for a password. What do you do?
Solution
On the destination server, run this (where x.x.x.x is the IP address of the server with the Git repo):
git clone git@x.x.x.x:root/goodrepo.git
If you are prompted for a password,
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Problem scenario
You run a command such as this, with the goal of printing the number of occurrences of “foo”:
grep -icR foo * | awk ‘{fs=”:”; print $2}’
It does not do what you want it to do. You want the field separator to be a colon. It is not working. How do you print the element after a “:” (colon) with an awk utility?
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Continue reading “How Do You Get awk to Use a Colon or a Semicolon as a Field Separator?”
Problem scenario
You want to test out a CDN in AWS. What do you initially deploy CloudFront?
Solution
Prerequisite
This assumes that you have an S3 bucket with read permissions. To do this, log into the Amazon S3 console and create a bucket. Upload files and configure the permissions to grant read permissions to anyone.
Procedures
AWS CloudFront has “Distributions.” You want to create a CloudFront Distribution.
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Problem scenario
You want to enter the MongoDB shell to enter commands interactively. What do you do?
Solution
1. Run this command: /usr/bin/mongo
If the command is not found, do two things:
a) Run this: sudo find / -name mongo | grep bin
b) Run the mongo file found above (as an executable).
2. From the prompt “>” enter a command such as this:
db
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Problem scenario
You try to start Logstash but you get this error: “main ERROR Could not create plugin of type class org.apache.logging.log4j.core.appender.RollingFileAppender for element RollingFile: “
What should you do?
Solution
Do one of the two options below.
#1 Solution (rather simple, for a one-time fix)
Do not start the process with the root or some other regular user.
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Problem scenario
You try to start the SonarQube service. It does not turn on or stay on. You go to the logs directory in the “sonar” subdirectory on the Linux server. Every time you run “sudo systemctl start sonar”, there are no corresponding log entries. You may find no logs at all. What should you do to troubleshoot SonarQube to start when the logs are not helping you?
Solution
1.
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Continue reading “What Do You Do If SonarQube Has No Logs and the Service Will Not Start?”
Problem scenario
You are running an Ansible playbook, but you get an error like this: “IOError: [Errno 13] Permission denied…”
How do you get the playbook to work?
Solution
If the playbook has a destination for a file and that file is already there on the managed node, this error may occur.
1. Go to the managed node.
2.
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Problem scenario
You want to run a basic Lua program as a test. What do you do?
Solution
Prerequisite
You must have installed the Lua compiler. If you are using a CentOS/RHEL/Fedora server, try this link.
Procedures
1. Create a file called contint.lua with the following line:
print(“This is a Hello World program”)
2. Run it with this command:
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Continue reading “How Do You Write a Hello World Program in Lua?”
Problem scenario
You want to test out the Golang compiler. You want to know how to write a basic Go program and run it. What do you do?
Solution
Prerequisites
You must have the Golang compiler installed. If you need help, see this posting.
Procedures
1. Create a file called hw.go with the following five lines:
package main
import “fmt”
func main() {
fmt.Println(“This is a Hello World program!”)
}
2.
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Continue reading “How Do You Write a Hello World Program in Golang?”
Problem scenario
You want to run Lua programs on your Red Hat derivative distribution of Linux server (e.g., CentOS/RHEL/Fedora).
Solution
1. Make a script like this called lua.sh with the following lines:
yum -y install readline-devel gcc
curl https://www.lua.org/ftp/lua-5.3.5.tar.gz > /tmp/lua-5.3.5.tar.gz
mv /tmp/lua-5.3.5.tar.gz /opt/
cd /opt/
tar -xzvf lua-5.3.5.tar.gz
cd lua-5.3.5
sudo make linux test
echo “ENV=$ENV:/opt/lua-5.3.5/src/” >>
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Continue reading “How Do You Install the Lua Compiler on a CentOS/RHEL/Fedora Server?”