[pull] master from bregman-arie:master

README.md

@@ -3953,10 +3953,31 @@ True
 
 <details>
 <summary>What is the workflow of retrieving data from Ceph?</summary><br><b>
+The work flow is as follows:
+
+1. The client sends a request to the ceph cluster to retrieve data:
+> **Client could be any of the following**
+>> * Ceph Block Device
+>> * Ceph Object Gateway
+>> * Any third party ceph client
+
+
+2. The client retrieves the latest cluster map from the Ceph Monitor
+3. The client uses the CRUSH algorithm to map the object to a placement group. The placement group is then assigned to a OSD.
+4. Once the placement group and the OSD Daemon are determined, the client can retrieve the data from the appropriate OSD
+
+
 </b></details>
 
 <details>
-<summary>What is the workflow of retrieving data from Ceph?</summary><br><b>
+<summary>What is the workflow of writing data to Ceph?</summary><br><b>
+The work flow is as follows:
+
+1. The client sends a request to the ceph cluster to retrieve data
+2. The client retrieves the latest cluster map from the Ceph Monitor
+3. The client uses the CRUSH algorithm to map the object to a placement group. The placement group is then assigned to a Ceph OSD Daemon dynamically.
+4. The client sends the data to the primary OSD of the determined placement group. If the data is stored in an erasure-coded pool, the primary OSD is responsible for encoding the object into data chunks and coding chunks, and distributing them to the other OSDs. 
+
 </b></details>
 
 <details>

certificates/aws-cloud-practitioner.md

@@ -1,6 +1,6 @@
 ## AWS - Cloud Practitioner
 
-A summary of what you need to know for the exam can be found [here](https://codingshell.com/aws-cloud-practitioner)
+A summary of what you need to know for the exam can be found [here](https://aws.amazon.com/certification/certified-cloud-practitioner/)
 
 #### Cloud 101
 

scripts/aws s3 event triggering/README.md

@@ -0,0 +1 @@
+[](./sample.png)

scripts/aws s3 event triggering/aws_s3_event_trigger.sh

@@ -0,0 +1,122 @@
+#!/bin/bash
+
+# always put up the detail of scripts . version, author, what it does, what event triggers and all .. 
+
+###
+# Author: Adarsh Rawat
+# Version: 1.0.0
+# Objective: Automate Notification for a object uploaded or created in s3 bucket.
+###
+
+# debug what is happening
+set -x
+
+# all these cmds are aws cli commands | abhishek veermalla day 4-5 devops
+
+# store aws account id in a variable
+aws_account_id=$(aws sts get-caller-identity --query 'Account' --output text)
+
+# print the account id from the variable
+echo "aws account id: $aws_account_id"
+
+# set aws region, bucket name and other variables
+aws_region="us-east-1" 
+aws_bucket="s3-lambda-event-trigger-bucket"
+aws_lambda="s3-lambda-function-1"
+aws_role="s3-lambda-sns"
+email_address="[email protected]"
+
+# create iam role for the project
+role_response=$(aws iam create-role --role-name s3-lambda-sns --assume-role-policy-document '{
+  "Version": "2012-10-17",
+  "Statement": [{
+    "Action": "sts:AssumeRole",
+    "Effect": "Allow",
+    "Principal": {
+      "Service": [
+        "lambda.amazonaws.com",
+        "s3.amazonaws.com",
+        "sns.amazonaws.com"
+      ]
+    }
+  }]
+}')
+
+# jq is json parser here parse the role we created 
+
+# extract the role arn from json resposne and store in variable
+role_arn=$(echo "$role_response" | jq -r '.Role.Arn')
+
+# print the role arn
+echo "Role ARN: $role_arn"
+
+# attach permissions to the role
+aws iam attach-role-policy --role-name $aws_role --policy-arn arn:aws:iam::aws:policy/AWSLambda_FullAccess
+aws iam attach-role-policy --role-name $aws_role --policy-arn arn:aws:iam::aws:policy/AmazonSNSFullAccess
+
+# create s3 bucket and get the output in a variable
+bucket_output=$(aws s3api create-bucket --bucket "$aws_bucket" --region "$aws_region")
+
+# print the output from the variable 
+echo "bucket output: $bucket_output"
+
+# upload a file to the bucket
+aws s3 cp ./sample.png s3://"$aws_bucket"/sample.png
+
+# create a zip file to upload lambda function 
+zip -r s3-lambda.zip ./s3-lambda
+
+sleep 5
+
+# create a lambda function
+aws lambda create-function \
+  --region $aws_region \
+  --function $aws_lambda \
+  --runtime "python3.8" \
+  --handler "s3-lambda/s3-lambda.lambda_handler" \
+  --memory-size 128 \
+  --timeout 30 \
+  --role "arn:aws:iam::$aws_account_id:role/$aws_role" \
+  --zip-file "fileb://./s3-lambda.zip"
+
+# add permissions to s3 bucket to invoke lambda
+LambdaFunctionArn="arn:aws:lambda:us-east-1:$aws_account_id:function:s3-lambda"
+aws s3api put-bucket-notification-configuration \
+  --region "$aws_region" \
+  --bucket "$aws_bucket" \
+  --notification-configuration '{
+    "LambdaFunctionConfigurations": [{
+        "LambdaFunctionArn": "'"$LambdaFunctionArn"'",
+        "Events": ["s3:ObjectCreated:*"]
+    }]
+}'
+
+aws s3api put-bucket-notification-configuration \
+  --region "$aws_region" \
+  --bucket "$aws_bucket" \
+  --notification-configuration '{
+    "LambdaFunctionConfigurations": [{
+        "LambdaFunctionArn": "'"$LambdaFunctionArn"'",
+        "Events": ["s3:ObjectCreated:*"]
+    }]
+}'
+
+# create an sns topic and save the topic arn to a variable
+topic_arn=$(aws sns create-topic --name s3-lambda-sns --output json | jq -r '.TopicArn')
+
+# print the topic arn
+echo "SNS Topic ARN: $topic_arn"
+
+# Trigger SNS topic using lambda function
+
+# Add sns topic using lambda function
+aws sns subscribe \
+  --topic-arn "$topic_arn" \
+  --protocol email \
+  --notification-endpoint "$email_address"
+
+# publish sns
+aws sns publish \
+  --topic-arn "$topic_arn" \
+  --subject "A new object created in s3 bucket" \
+  --message "Hey, a new data object just got delievered into the s3 bucket $aws_bucket" 

scripts/aws s3 event triggering/s3-lambda/requirements.txt

@@ -0,0 +1 @@
+boto3==1.17.95

scripts/aws s3 event triggering/s3-lambda/s3-lambda.py

@@ -0,0 +1,38 @@
+import boto3
+import json
+
+def lambda_handler(event, context):
+
+  # i want to know that event thing
+  print(event)
+
+  # extract relevant information from the s3 event trigger
+  bucket_name=event['Records'][0]['s3']['bucket']['name']
+  object_key=event['Records'][0]['s3']['object']['key']
+
+  # perform desired operations with the upload file
+  print(f"File '{object_key}' was uploaded to bucket '{bucket_name}'")
+
+  # example: send a notification via sns
+  sns_client=boto3.client('sns')
+  topic_arn='arn:aws:sns:us-east-1:<account-id>:s3-lambda-sns'
+  sns_client.publish(
+    TopicArn=topic_arn,
+    Subject='s3 object created !!',
+    Message=f"File '{object_key}' was uploaded to bucket '{bucket_name}"
+  )
+
+  # Example: Trigger another Lambda function
+  # lambda_client = boto3.client('lambda')
+  # target_function_name = 'my-another-lambda-function'
+  # lambda_client.invoke(
+  #    FunctionName=target_function_name,
+  #    InvocationType='Event',
+  #    Payload=json.dumps({'bucket_name': bucket_name, 'object_key': object_key})
+  # )
+  # in case of queuing and other objective similar to the netflix flow of triggering
+
+  return {
+    'statusCode': 200,
+    'body': json.dumps("Lambda function executed successfully !!")
+  }

topics/aws/README.md

@@ -1,16 +1,16 @@
 # AWS
 
-**Note**: Some of the exercises <b>cost $$$</b> and can't be performed using the free tier/resources
+**Note**: Some of the exercises <b>cost $$$</b> and can't be performed using the free tier or resources
 
-**2nd Note**: Provided solutions are using the AWS console. It's recommended you'll use IaC technologies to solve the exercises (e.g. Terraform, Pulumi).<br>
+**2nd Note**: The provided solutions are using the AWS console. It's recommended you use IaC technologies to solve the exercises (e.g., Terraform, Pulumi).<br>
 
 - [AWS](#aws)
   - [Exercises](#exercises)
     - [IAM](#iam)
     - [EC2](#ec2)
     - [S3](#s3)
     - [ELB](#elb)
-    - [Auto Scaling Groups](#auto-scaling-groups)
+    - [Auto Scaling Groups] (#auto-scaling-groups)
     - [VPC](#vpc)
     - [Databases](#databases)
     - [DNS](#dns)
@@ -24,14 +24,14 @@
     - [Global Infrastructure](#global-infrastructure)
     - [IAM](#iam-1)
     - [EC2](#ec2-1)
-      - [AMI](#ami)
-      - [EBS](#ebs)
-      - [Instance Store](#instance-store)
-      - [EFS](#efs)
-      - [Pricing Models](#pricing-models)
-      - [Launch Template](#launch-template)
-      - [ENI](#eni)
-      - [Placement Groups](#placement-groups)
+    - [AMI](#ami)
+    - [EBS](#ebs)
+    - [Instance Store](#instance-store)
+    - [EFS](#efs)
+    - [Pricing Models](#pricing-models)
+    - [Launch Template](#launch-template)
+    - [ENI](#eni)
+    - [Placement Groups](#placement-groups)
     - [VPC](#vpc-1)
       - [Default VPC](#default-vpc)
     - [Lambda](#lambda-1)
@@ -63,7 +63,7 @@
     - [SNS](#sns)
     - [Monitoring and Logging](#monitoring-and-logging)
     - [Billing and Support](#billing-and-support)
-      - [AWS Organizations](#aws-organizations)
+    - [AWS Organizations](#aws-organizations)
     - [Automation](#automation)
     - [Misc](#misc-2)
     - [High Availability](#high-availability)
@@ -3485,6 +3485,6 @@ More details are missing to determine for sure but it might be better to decoupl
 <details>
 <summary>What's an ARN?</summary><br><b>
 
-ARN (Amazon Resources Names) used for uniquely identifying different AWS resources.
-It is used when you would like to identify resource uniqely across all AWS infra.
+ARN (Amazon Resources Names) are used for uniquely identifying different AWS resources.
+It is used when you would like to identify resource uniqely across all AWS infrastructures.
 </b></details>

topics/cloud/README.md

@@ -91,6 +91,16 @@ AWS definition: "AWS Auto Scaling monitors your applications and automatically a
 Read more about auto scaling [here](https://aws.amazon.com/autoscaling)
 </b></details>
 
+<details>
+<summary>What is the difference between horizontal scaling and vertical scaling?</summary><br><b>
+
+[AWS Docs](https://wa.aws.amazon.com/wellarchitected/2020-07-02T19-33-23/wat.concept.horizontal-scaling.en.html):
+
+A "horizontally scalable" system is one that can increase capacity by adding more computers to the system. This is in contrast to a "vertically scalable" system, which is constrained to running its processes on only one computer; in such systems the only way to increase performance is to add more resources into one computer in the form of faster (or more) CPUs, memory or storage.
+
+Horizontally scalable systems are oftentimes able to outperform vertically scalable systems by enabling parallel execution of workloads and distributing those across many different computers.
+</b></details>
+
 <details>
 <summary>True or False? Auto Scaling is about adding resources (such as instances) and not about removing resource</summary><br><b>
 
@@ -105,4 +115,4 @@ False. Auto scaling adjusts capacity and this can mean removing some resources b
   * Instance should have minimal permissions needed. You don't want an instance-level incident to become an account-level incident
   * Instances should be accessed through load balancers or bastion hosts. In other words, they should be off the internet (in a private subnet behind a NAT). 
   * Using latest OS images with your instances (or at least apply latest patches)
-</b></details>
+  </b></details>

topics/linux/README.md

@@ -360,6 +360,7 @@ It contains useful information about the processes that are currently running, i
 
 <details>
 <summary>What makes /proc different from other filesystems?</summary><br><b>
+/proc is a special virtual filesystem in Unix-like operating systems, including Linux, that provides information about processes and system resources.
 </b></details>
 
 <details>
@@ -433,6 +434,10 @@ Its a bit that only allows the owner or the root user to delete or modify the fi
 
 <details>
 <summary>What is sudo? How do you set it up?</summary><br><b>
+sudo is a command-line utility in Unix-like operating systems that allows users to run programs with the privileges of another user, usually the superuser (root). It stands for "superuser do.
+
+The sudo program is installed by default in almost all Linux distributions. If you need to install sudo in Debian/Ubuntu, use the command apt-get install sudo
+
 </b></details>
 
 <details>
@@ -2138,6 +2143,20 @@ This is a good article about the topic: https://ops.tips/blog/how-linux-creates-
 
 <details>
 <summary>You executed a script and while still running, it got accidentally removed. Is it possible to restore the script while it's still running?</summary><br><b>
+It is possible to restore a script while it's still running if it has been accidentally removed. The running script process still has the code in memory. You can use the /proc filesystem to retrieve the content of the running script.
+1.Find the Process ID by running 
+```
+ps aux | grep yourscriptname.sh
+```
+Replace yourscriptname.sh with your script name.
+2.Once you have the PID, you can access the script's memory through the /proc filesystem. The script will be available at /proc/<PID>/fd/, where <PID> is the process ID of the running script. Typically, the script's file descriptor is 0 or 1.
+
+You can copy the script content to a new file using the cp command:
+```
+cp /proc/<PID>/fd/0 /path_to_restore_your_file/yourscriptname.sh
+```
+Replace <PID> with the actual PID of the  script and /path_to_restore_your_file/yourscriptname.sh with the path where you want to restore the script.
+
 </b></details>
 
 <a name="questions-linux-memory"></a>