How Do You Troubleshoot Adding Red Hat Packages with Errors Like “Curl error (77): Problem with the SSL CA cert (path? access rights?)”?

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Problem scenario
You try to run a DNF command, but you get stymied with errors like these:

Fedora 32 foobar (From SomeCompany) – x86_64 0.0 B/s | 0 B 00:00
Errors during downloading metadata for repository ‘fedora-somecompany-foobar’: – Curl error (77): Problem with the SSL CA cert (path? access rights?) for https://mirrors.fedoraproject.org/metalink?repo=fedora-somecompany-foobar-32&arch=x86_64 [error setting certificate verify locations:
CAfile: /etc/ssl/certs/ca-certificates.crt
CApath: /etc/ssl/certs]
Cannot prepare internal mirrorlist: Curl error (77): Problem with the SSL CA cert (path?

…

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How Do You Fix a White/Blank Web Page?

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Problem scenario
You have a white screen in the web browser. Why is the website just white when using HTML?

Possible Solution #1
Are the font and background color the same? If the font is set to be white, that may be the problem. HTML has hexadecimal codes for the font and background color; you can view them here: https://htmlcolorcodes.com/

Possible Solution #2
Is there a misspelling in the URL and the ultimate web page?

…

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How Do You Use Nomics to a Retrieve Cryptocurrency Prices?

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Problem scenario
You want to use Nomics to retrieve cryptocurrency prices. What do you do?

Prerequisite
Get an API key. It is free here: https://p.nomics.com/pricing#free-plan
(You do not need to provided credit card information to obtain one.)

Procedures
Run this Python program but replace YOUR_KEY_HERE with the key:

import requests
resp = requests.get(“https://api.nomics.com/v1/prices?key=YOUR_KEY_HERE&format=json”)
for item in resp.json():
if item[’currency’] in [”BTC”, …

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How Do You Troubleshoot WordPress Posting Previews That Don’t Wrap on One Page?

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Problem scenario
You have a website powered by WordPress. You see a big gulf of space between your widgets/ads and your posting previews. It only happens on one page of previews (not other pages). The ads are too far to the right when the preview doesn’t wrap. Why are your previews not wrapping on one page?

Solution
The problem may be one posting.

…

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How Do You Eliminate Unintended Indentation in Code?

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Problem scenario
You are using WordPress for you website. You have code that has an indentation of one to three spaces that you do not want. You did not intend for this indentation. It is usually just one line — the top line.

Here is an example:

How can you eliminate this indentation of your code?

Solution
Root cause
If you have a new line in the paragraph,

…

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How Do You Write a Flask Program to Accept a Parameter in the URL?

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Problem scenario
You want to pass a variable via a URL to a Python program. You want to use Flask for this. What do you do?

Solution
Prerequisite
Install Flask. If you need assistance, see this posting if you are using a CentOS/RHEL/Fedora server or this posting if you are using a Debian/Ubuntu server.

Procedures
This is a multi-route Flask program.

…

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How Do You Troubleshoot the Flask Message “LookupError: the converter ‘str’ does not exist”?

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Problem scenario
You are trying to pass a string parameter to a Flask application via a call to a URL. You get the message “LookupError: the converter ‘str’ does not exist.” What should you do?

Solution
Use the term “string” instead of “str”.

Here is an example of incorrect syntax:
@app.route(“/ccc/”, strict_slashes=False)

This shows the correct syntax:
@app.route(“/ccc/”,

…

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How Do You Go to an ELB from Your Workstation?

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Problem scenario
You can go to an ELB’s FQDN via an EC-2 instance (with a curl command). But you cannot go to an ELB from your workstation (with a web browser). What should you do?

Possible solution #1
From the EC-2 instance, can you use nslookup FQDNofELB (where FQDNofELB is the FQDN of the ELB)? This should provide you with the IP address (the last of the IP addresses in the results).

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How Do You Troubleshoot Connectivity over Port 80 when You Know It Is Listening?

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Problem scenario
A server is hosting a website. On the server, nmap -Pn x.x.x.x is showing port 80 is listening on the server itself. From another server this nmap -Pn x.x.x.x command is showing no ports (or a subset of the ports) are listening. What is the cause of this?

Possible Solution #1
There is a firewall on the webserver that is causing this.

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How Do You Build a Flask Application to Return the Price of a Cryptocurrency?

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Problem scenario
You want to write a Flask program to display the high and low prices of a given cryptocurrency for a given day. You want the output to include the volume too. How do you do this?

Solution
Prerequisite
This assumes that you have installed Flask and pandas.

Procedures
Run this program.

…

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