A Technical I.T./DevOps Blog
Problem scenario
You backed up /var/log/mail to a different file. You want the /var/log/mail file to start empty so you can review it without looking at old activity. What do you do?
Solution
Run these four commands:
sudo su –
cd /var/log
mail
exit
Now you /var/log/mail file will still exist and record activity as normal. It will not have anything in it before the time you ran the above “>
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Continue reading “How Do You Zero out a /var/log/mail File?”
Problem scenario
In Linux you want to delete files that have not been modified in the past three days from the /tmp/ directory. What do you do?
Solution
Run this: find /tmp/ -maxdepth 1 -type f -atime -3 -ls | awk ‘{print $NF}’ | rm -rf
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Continue reading “How Do You Delete Files That Were Modified More Than Three Days Ago?”
Problem scenario
You see two underscores or two underbars before a function in Python. What does this syntax signify?
Possible Solution #1
The answer is best explained by running this program once with no modification and a second time with a modification.
class ContintClass():
def __init__(self):
self.__completelyprivate = “1111111111”
self._semiprivate = “2222222”
foo = ContintClass()
#print(foo.__completelyprivate)
print(“Above is an attempt to print a completely private data member of an object”)
print(“Below is an attempt to print a semi-private data member of an object”)
print(foo._semiprivate)
Before you run the program the second time,
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Problem scenario
The elasticsearch, logstash or kibana services will start, but when you check the status, it does not remain on. It keeps stopping. You see the status as “failed.”
Solution
Possible Solution #1
Add more memory or swap space to the system. If you need assistance with either of these, see this posting.
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Continue reading “How Do You Get the ElasticSearch, LogStash or Kibana Service to Remain On?”
Problem scenario
You have a Python program with print statements. When you run the program, you get twice as many print statements as you expect. What could be wrong?
Possible Solution #1
Do not name the program re.py or string.py. When you name the program re.py and have an import re statement, Python may print every line it is supposed to print twice.
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Continue reading “Why is Your Python Programming Printing Duplicate Lines?”
Problem scenario
You want to create a .txt file that has 50 key-value pairs. You want the keys to be whole numbers. You want the values to be five-character strings. What should you do?
Solution
import random
import string
import sys
def randomword(length):
letters = string.ascii_lowercase
return ”.join(random.choice(letters) for i in range(length))
def printer(counter, webstera):
webstera[counter] = randomword(5)
if (counter < …
Continue reading “How Do You Write a Python Program to Create a .txt File with 50 Key-Value Pairs?”
Prerequisites
This assumes you have installed Java. If you need assistance with installing Java, see this posting. This assumes you have a server with 4 GB of memory (e.g., virtual memory and RAM in an amount greater than 4 GB). The command to run to see how much memory you need is this one: free -mh If you need more memory, see this posting.
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Continue reading “How Do You Install ElasticSearch on CentOS/RHEL/Fedora?”
Problem scenario
When you run your Python program, you get this message: “AttributeError: module ‘re’ has no attribute ‘IGNORECASE'”
What should you do to get your program to work correctly?
Solution
Change the name of the program to something different. Do not name your program “re.py”. If you use the “import string” and your program is called “re.py”, you may get this error.
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Problem scenario
You run a docker command, but you get “port bindings are not yet supported by rootless containers”. What should you do?
Solution
Use sudo before the Docker command.
Waning: The above is not recommend for security purposes. Only follow this direction (with sudo docker run…), if the server is not that important or you are in a very secure network.
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Problem scenario
You are not sure if you have valid JSON or not. You have converted raw logs of an application to be in JSON format. There is a flat file receiving what you believe to be valid JSON. How do you know for sure?
Solution
Put the JSON in here https://jsonformatter.curiousconcept.com/ and click “Process”.
The JSON should start with an opening brace { and end with a closing brace }.
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Continue reading “How Do You Know if Your Logging is Truly in JSON Format or Not?”