What Does SLS Stand for?

Question
You often see the initialism SLS. What does it stand for?

Answers
SLS disambiguation

1. Salt State System. SaltStack uses .sls files. “The core of the Salt State system is the SLS, or SaLt State file.” (This quote was taken from this site.)

2. Scheduler Load Simulator (as in YARN SLS). To read more about this,

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How Do You Troubleshoot an External Monitor That Does Not Work and You Cannot See Any Reference to It in the Windows Control Panel?

Problem scenario
With an HDMI cable you cannot get an external monitor that is connected to your Windows computer to work. In the Control Panel section for “Screen Resolution” there is a drop down menu for “Display.” This will give some descriptive identification of your monitor when the monitor is working properly. It does not show an attached monitor. What should you do if the “Display” drop down in Screen Resolution (in the Windows Control Panel) does not show your monitor and the external monitor is not working to display any output?

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How Do You Send an Email from the Command Prompt of Linux to a Long List of Recipients?

Problem scenarios
One or both of the following apply:

#1 You want to automate the sending of the exact same email to multiple people. You do not want to manually type in the recipients. You have the same subject and body that each recipient should receive. You want to customize the “from address” that the recipients see. How do you do this?

OR

#2 You are using the mail command on a Linux server.

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How Do You Programmatically Search Hyperlinks on a Given Webpage?

Problem scenario
You have a web page that you access from the front-end (e.g., a web browser). You want to see if there is a hyperlink on the page that goes to a certain URL. You know the web page and the URL, but you are not sure if a hyperlink on the website has such a link. What should you do?

Solution
Use the curl command.

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How Do You Troubleshoot the Puppet Error “file mode specification must be a string, not ‘Integer'”?

Problem scenario
You are running a manifest and you get this error:

Error: Failed to apply catalog: Parameter mode failed on File[/opt/hadoop/hadoop-2.2.0.tar.gz]: The file mode specification must be a string, not ‘Integer’ at /etc/puppetlabs/code/environments/production/modules/hadoop/manifests/init.pp:55

What is wrong?

Solution
Go to the Puppet Master server and open the file in the error. (The error provides the full directory path.) Go to the line number that the error message specifies.

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How Do You Create a Puppet Manifest to Install Java?

Problem scenario
You have Puppet agent and Puppet Master set up and configured to work together. You are are running open source Puppet 5.x on Ubuntu servers in AWS. You want to install Java on the Puppet agent nodes. You tried to use the Java module.

On the Puppet Master server, you ran this: puppet module install puppetlabs-java –version 2.2.0

This is your site.pp file:

class { ‘java’ :
package =’java-1.8.0-openjdk-devel’,  » Read more..

How Do You Capture More Events in the Nginx Logs?

Problem scenario
You want more verbose log capturing in Nginx. What should you do?

Solution
1. Make a back up of nginx.conf. Then open it. It is often in /etc/nginx/nginx.conf. (Some versions of nginx have a file that does some of the same things called default.conf. This will be the file you will need if you have no nginx.conf file.)

2.

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How Do You Troubleshoot Puppet Agent with a “Failed to open TCP connection…connection refused port 8140” error?

Problem scenario
You run puppet agent but you get this error:

Error: Could not request certificate: Failed to open TCP connection to puppetmaster.domain.com:8140 (Connection refused – connect(2) for “puppetmaster.domain.com” port 8140)

What do you do?

Solution
Ensure port 8140 is open. Install nmap on a server, and run this command:

nmap -p 8140 puppetmaster.domain.com

If you see this

PORT STATE SERVICE
8140/tcp closed unknown

Then the Puppet Master service is not running.

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How Do You Troubleshoot the Puppet Problem “Error 500 on SERVER: … Could not find node statement with name ‘default’ or “?

Problem scenario
You run the Puppet agent on a server but you receive this error:

Error: Could not retrieve catalog from remote server: Error 500 on SERVER: Server Error: Could not find node statement with name ‘default’ or ‘ip-172-31-20-105.us-east-2.compute.internal, ip-172-31-20-105.us-east-2.compute, ip-172-31-20-105.us-east-2, ip-172-31-20-105’ on node ip-172-31-20-105.us-east-2.compute.internal
Warning: Not using cache on failed catalog
Error: Could not retrieve catalog; skipping run

What should you do?

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How Do You Send an Email via a Postfix Server on Linux with the Command Prompt That Has Multiple Recipients and a Subject?

Problem scenario
You want to send one email to multiple people. You tried separating the email addresses with a comma or semicolon but you received this message: “555 5.5.4 Unsupported option:”

You do not know how to send an email with a subject via the Postfix command prompt. How do you send an email to multiple people with “Re:” content of your choice?

Solution
Prerequisite
You need to have Postfix installed and configured.

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