DEV Community: Linux_guy

Terraform with AWS

Linux_guy — Tue, 30 Sep 2025 15:58:11 +0000

Maine Goal : Primary goal of this post is to explain core concept of terraform
Terraform : Infrastructure as Code Tool

Services : Basic AWS Services to demonstrate terraform concept

Virtual Machine ( EC2 )
Firewall ( Security Groups )
AWS Users ( IAM Users )
IP Address ( Elastic IP )

Basics of Firewall

Ports

ports acts as a endpoint of communication to identify a given application or process on an linux operating system
to know what ports are opened on a system we use netstat -ntlp

Firewall

it's network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules
for AWS we call it as security group
Create Security group using terraform

resource "aws_security_group" "allow_tls" {
  name = "allow_tls"
  description = "Managed from Terraform | Allow TLS inbout traffic and all outbound traffic"
  vpc_id = aws_vpc.main.id

  tags = {
    Name = "allow_tls"
  }
}

Block of code to add inboud or outboud rules to terraform

// Ingress : inbound rules
// Egress : Outbound rules
resource "aws_vpc_security_group_ingress_rule" "allow_tls_ipv4" {
  security_group_id = aws_security_group.allow_tls.id
  cidr_ipv4 = aws_vpc.main.cidr_block
  from_port = 80
  ip_protocol = "tcp"
  to_port = 80
}

resource "aws_vpc_security_group_egress_rule" "allow_all_traffic_ipv4" {
  security_group_id = aws_security_group.allow_tls.id
  cidr_ipv4 = "0.0.0.0/0"
  ip_protocol = "-1" # semantically equivalent to all ports
}

SSH Tutorial

Linux_guy — Wed, 16 Jul 2025 02:34:56 +0000

Create ssh keys

to create new ssh key we use this command

ssh-keygen -t rsa -b 4096 -C "comment" -f "key-name"

after running this command two files will be generated. copy the contents of file with .pub extension and paste it on to remote hosts .ssh/authorized_keys file

Installing Locate Package

Linux_guy — Tue, 04 Mar 2025 15:13:27 +0000

To install locate command follow the steps

Install mlocate package

sudo yum install -y mlocate

Run updatedb commands to build database of current files

sudo updatedb

Docker Basics

Linux_guy — Thu, 09 Jan 2025 11:43:49 +0000

Docker basics
Docker working with containers
Docker images
Docker Volumes
Docker Networking
Docker Compose
Docker Debug & Monitoring
Clean Up

Docker Basics

To know currently Running docker version

docker --version

To get detailed information about docker installation

docker info

to get help with docker use

docker help

Working with Containers

to run a docker container

# docker run [options] image-name [command] [args]
# ex.
docker run nginx
# this will run container in detached mode
docker run -d nginx

to list running containers

docker ps

to list all the containers running or stopped

docker ps -a

to stop a running stop

# docker stop [container_id/name]
docker stop nginx

to start a stopped container

# docker start [container_id/name]
docker start nginx

to restart a container

# docker restart [container_id/name]
docker restart nginx

to remove a stopped container

# docker rm [container_id/name]
docker rm nginx

to check logs of a container

# docker logs [container_id/name]
docker logs nginx

to execute a command in a running container

docker exec -it [container_id] <command>

to get detailed information about a container

docker inspect [container_id]

to get real-time usage stats of a running container

docker stats

Docker images

to list all the docker images

docker images

to download an image from docker hub

# docker pull [image_name]
docker pull nginx

to push a docker image to a registry

docker push [image_name]

to export docker image to a tar file we use

docker save -o <file>.tar [image_name]

to import docker image from tar file

docker load -i <file>.tar

to build an image from a docker file

# docker build -t [IMAGE_NAME:TAG]
docker build -t [image_name]

to remove an docker image

# docker rmi [IMAGE_NAME:TAG
docker rmi nignx

Docker volume

to create a docker volumes

# docker volume create [VOLUME_NAME]
docker volume create [VOLUME_NAME]

to list all the volumes

docker volume ls

to remove a volume

docker volume rm [VOLUME_NAME]

to mount a volume to a container

docker run -v <volume>:/path/in/container [image_name]

Docker networking

to list all the docker networks

docker network ls

to create docker network

docker network create [NETWORK_NAME]

to connect a container to a specific docker network

docker network connect [NETWORK_NAME]

view details about specific docker network

docker network inspect [NETWORK_NAME]

Docker Compose

start all the service defined in a yaml file

docker-compose up

to get logs

docker-compose logs

build images defined in a docker-compose.yml file

docker-compose build

stop and remove all servies defined in the file

docker-compose down

list all services managed by compose

docker-compose ps

Debugging and monitoring

run a command inside a running container

docker exec -it [container_id/name]

View detailed information about a container or image

docker inspect [container_id/name]

monitor resource usage of container

docker stats

Clean up

remove unused data(stopped container, images, networks)

docker system prune -a

remove unwanted containers

docker container prune

remove unused images

docker image prune -a

remove unused volume

docker volume prune

END

DSA Using C++

Linux_guy — Sat, 21 Dec 2024 20:19:50 +0000

Starting with Pointers

Code without Pointers

# include <iostream>

using namespace std;

int main() {
    // defining number 1
    int num1 = 11;
    // defining number 2
    int num2 = num1;

    // redefining num1
    num1 = 22;

    // print out the num1 and num2
    cout << "num1 = " << num1 << endl;
    cout << "num2 = " << num2 << endl;

}

Result : value will be different in both num1 and num2

Code with Pointers

# include <iostream>

using namespace std;

int main() {

    // defining num1 using pointer
    int* num1 = new int(11);

    // defining num2 using pointer
    int* num2 = num1;

    // print out the num1 and num2
    cout << "num1 = " << *num1 << endl;
    cout << "num2 = " << *num2 << endl;

}

Result : value will be same in both num1 and num2

Python : OS Module Introduction

Linux_guy — Tue, 15 Oct 2024 23:54:13 +0000

OS module

in order to import OS module we use

import os

To print all the available options in a method/function

import os

print(dir(os))

to print Current working directory we use

import os

print(os.getcwd())

to print directory location we use

import os
path='/home/user/'

# printing path before changing directory
print(os.getcwd())

# function used for changing directory
os.chdir(path)

# printing path after changing directory
print(os.getcwd())

# to list directories
print(os.listdir())

To make a single directory without any intermediate directories

import os

# this wont create intermediate directories
os.makedir('single_dir')

print(os.listdir())

To make a multiple directories with intermediate directories

import os

# this will create intermediate directories
os.makedirs('parent_dir/child_dir')

print(os.listdir())

To remove a single directory

import os

# this wont remove intermediate directories
os.rmdir('path')

print(os.listdir())

To remove a multiple directory

import os

# this will remove intermediate directories
os.removedirs('path1/path2')

print(os.listdir())

To rename a directory

import os

# this will remove intermediate directories
os.rename('old-name','new-name')

print(os.listdir())

To print information about OS, we use os.stat() function

import os
import datetime from datetime

# this will remove intermediate directories
print(os.stat('file-name'))

# Example : to print when file was created 
file_created = os.stat('file-name').st_mtime
print(datetime.fromtimestamp(file_created))

To list information about directories & Subdirectories

import os

path = os.chdir('path')

# Example : to print all the files under that above path 
for dirpath, dirname, filename in os.walk():
    print('Current Path:',dirpath)
    print('Directories:',dirname)
    print('filename:',filename)
    print()

To print Environment variables

import os

# to print Environment variable home
print(os.environ.get('HOME'))

To interact with path we use os.path module
Examples of path module

import os 

# to check if given path exists or not 
print(os.path.exists('/home/user1/text.txt'))

# to check if given path is a directory or file
print(os.path.isdir('/home/user2/demo'))
print(os.path.isfilek('/home/user2/demo'))

# to split filname name from extenstion we use
print(os.path.splitext('/home/demo1/book.txt'))

# to print basename of any file we use
print(os.path.basename('/home/demo1/book.txt'))
# to print the directory name we use
print(os.path.dirname('/home/demo1/book.txt'))
# to print both, dirname + basename we use
print(os.path.split('/home/demo1/book.txt'))

# to join paths we use
file_path = os.path.join(os.environ.get('HOME'),'test.txt')
print(file_path)

Bash Script using Python

Linux_guy — Sat, 28 Sep 2024 14:30:00 +0000

have you ever felt stuck while writing bash script, which becomes complex over time and you find no other way to make it easier?

in this blog, I'll try to demonstrate, how I've integrated the Python module with a bash script to make it easier.

What do we need? 📝

Basic Python understanding
Bash scripting
free time to play with it

How to run a simple bash command using python 🎯

#!/bin/python3

# import subprocess modules
import subprocess as sp

# run subprocess 
sp.run('ls',shell=True)

Output:

passing argument as a list 🔐

For security reasons we don't enable shell=True, instead we pass command arguments via a list in the process

#!/bin/python3

# import subprocess modules
import subprocess as sp

# run subprocess
p1=sp.run(['ls','-la'],capture_output=True,text=True)

# text=True: this option converts the output into a string instead of a binary
# capture_output=True: this option directs output to be stored in a variable instead of directing it to the console

# printing the output
print(p1.stdout)

# more explanation:
# p1.stdout: this prints the standard output of the process
# p1.stderr: this will print the standard error of the process
# p1.returncode: this will print the return code for a process
# zero: if the command ran successfully
# non-zero: if command failed in execution

Output:

Redirecting output to a file ➡️📁

We can also store the output of a command to file

#!/bin/python3

# import subprocess modules
import subprocess as sp

# run subprocess
p1=sp.run(['ls','-la'],capture_output=True,text=True)

# using file handling we can output content of the process p2 to a file
with open('date.txt','w') as f:
    p2=sp.run(['date'],stdout=f,text=True)

Output:

What if!! we get an error!! 😲

Usually python doesn't give an error by default if a command results in an error
to fix this we use the check argument in the subprocess command

#!/bin/python3

# import subprocess modules
import subprocess as sp

# run subprocess
p1=sp.run(['ls','-la','-e'],capture_output=True,text=True,check=True)

# printing the output
print(p1.stderr)

Output:

What if!! 🤔 we want to discard the error

to discard the error in bash we redirect it to the > /dev/null
to make the same happen using Python we use

#!/bin/python3

# import subprocess modules
import subprocess as sp

# run subprocess
p1=sp.run(['ls','-la','-e'],stderr=sp.DEVNULL)

# printing the output
print(p1.stderr)

Output:

Reading 📖 a file 📁

to read a file we use cat command

#!/bin/python3

# import subprocess modules
import subprocess as sp

# run subprocess
p1=sp.run(['cat','sample-file.txt'],capture_output=True,text=True)

# printing the output
print(p1.stdout)

Output:

grep the contents of the file

to grep the contents of the file we can use output of the previous process as input to the other process.

#!/bin/python3

# import subprocess modules
import subprocess as sp

# run subprocess to cat
p1=sp.run(['cat','sample-file.txt'],capture_output=True,text=True)

# run subprocess to grep
p2=sp.run(['grep','-n','text'],capture_output=True,text=True,input=p1.stdout)

# printing the output
print(p2.stdout)

Output:

⚠️ Advanced ⚠️ !! content here!

whenever we run a command using subprocess.run it holds the console till the command execution is completed, this can be time-consuming in some cases.
to fix this we use Popen() method from subprocess

#!/bin/python3

# import subprocess modules
import subprocess as sp

# running a subprocess
p1=sp.Popen(['ping','-n', '10','google.com'],capture_output=True,text=True)

#checking for the output
p1.poll()

stdout,stderr = p1.communicate()

# explanation
# In the above command, it will ping Google 10 times
# During that process p1.poll() command will be used to check out if the above command has finished running or not

Grid Engine Commands

Linux_guy — Mon, 23 Sep 2024 16:27:17 +0000

QSTAT Command

To check the status of the jobs we use the qstat command

qstat

# to get information about specific job
qstat -j <job-id>

# to get the full information of the resources
qstat -f 

# to get the full details of all the jobs running
qstat -F

# To get the filter for a queue we use
qstat -q queue_list

# to filter by queue state 
qstat -qs {a|c|d|o|s|u|A|C|D|E|S}

# to filter jobs by users
qstat -u <userid>

# to show all user's job
qstat -u \*

QSUB

To submit a batch job we use the qsub command

# Example 1: to submit a simple bash job
qsub <script_path>

# Example 2: To submit an advanced batch job we use
qsub -cwd -S /bin/bash -i /data/example.in -o /results/example.out -j y example.sh arg1 arg2
# Options explained:
# -cwd: job will be executed from the same directory
# -S: bash shell will be assigned to interpret the submitted job
# -i: this file will be used as an input
# -o: this file will be used to show output
# -j y: this will merge the error into the same as the output file

# Example 3: advanced script
qsub -N example3 -P project_test -p -28 -l a=lx-amd64 example.sh
# Options explained:
# -N: this will be submitted by the given name, instead of the script name
# -P: this job will be submitted to project_test
# -p: this will assign lower priority to the given job than normal priority
# -l: this will request for amd64 resource on the scheduler

# Example 4: to submit a binary job
qsub -b y firefox

Job Submission Script

#!/bin/bash

#$ -N example3
#$ -P "project-name"
#$ -o test.out -e error.err
#$ -l mem=6G
#$ -l cpu=2

# command to be executed
echo "just a test"

QDEL

qdel is used to delete a job in the queue

# Force delete a job in the queue
qdel -f <job-id>

# to delete specific tasks of a job
qdel <job-id> -t <task-range>

# to delete all the jobs from a specific user, only possible for managers
qdel -u <user-list> "*"

How to check for the list of the nodes

To check the list of the current nodes we use the qhost command

qhost

# To check the jobs running under the specific hosts we use
qhost -q -j

Working With Shell

Linux_guy — Thu, 12 Sep 2024 18:12:55 +0000

What is a shell?

Linux shell is a program that allows text-based interaction between the user and the computer

Types of shell in Linux

Linux Commands

Linux command consists of program name followed by the option and arguments.
For ex.

cat -n myfile

# program name: cat
# option: -n
# argument: myfile

Home directory

The home directory is a directory that stores user-specific data.
this data can be of any type
for ex. If there is a user named john, then john's data like images, documents, downloads, etc. data will reside in /home/john/ location

How to know the Home directory

echo $HOME
# This command will read from the environment variable $HOME

echo ~
# This command will expand the tilde symbol to the given user's home directory path

Directory Management

How to know your current path

To know the current path, we use the command pwd, which stands for Present working directory

pwd

How to create & remove directories

mkdir is a command that is used to create a directory
rmdir is a command that is used to delete an empty directory
example

# to create a directory
mkdir test_directory

# to create multiple directories
mkdir test1 test2 test3

# to delete a directory
rmdir test_directory

# to remove multiple directories
rmdir test1 test2 test3

How to list the content of a folder

to list the content of a directory we use the ls command

# to list the content of a directory
ls

How to create a chain of directories

in order to perform this we use the "-p" parameter with mkdir command
Example

# We want to create 4 directories each inside of it's parent directory
mkdir -p a/b/c/d

How to navigate through directories

To switch directories we use cd command

# Changing to the parent directory
cd ../

# Changing to the home directory
cd /home/user1

How to navigate folder directory in Linux

there are two types of path notation in Linux
1. Relative Path
2. Absolute Path

Relative path

relative path is defined with respect to the current directory
"." represents the current working folder
".." represents the parent directory
For example

# to change to the parent directory for the current directory
cd ../

# to run a file/script present in the current directory
bash ./example.sh

Absolute path

absolute paths are defined with respect to the root "/" location
for example

# navigating to the user1 document folder
cd /home/user1/documents

PUSHD & POPD

pushd and popd commands are used to manage the directory stack.
Example

# we created 3 directories
mkdir -p a/b/c

# now we navigate to c directory using pushd command, by pushing it's path to directory stack
pushd a/b/c

# this command will take us to the given c directory and we can create a file here
echo "hello world" > test_file.txt

# to navigate to the previous path we can use popd command
# this will bring us to the parent directory
popd

Terraform Beginners Blog

Linux_guy — Mon, 02 Sep 2024 11:29:24 +0000

To install Terraform

for more updated info refer to the official website link.
Documentation

# download and install yum utils
sudo yum install -y yum-utils

# add the respective repository
sudo yum-config-manager --add-repo https://rpm.releases.hashicorp.com/RHEL/hashicorp.repo

# install the terraform
sudo yum -y install terraform

How to create a resource in Terraform

Resource blocks

resource Blocks are the basic Building blocks in HCL language
to create a resource block we define, resource keyword followed by Resource Type and it's name
example is given below

Terraform Workflow

It consists of 4 major steps
Config file : write the config file, which mentions what changes to be made in infrastructure
terraform init : run this command to initialize the modules and prepare it for execution.
terraform plan : run this command to plan and review, about the changes that will be made in the infrastructure.
terraform apply : run this command to apply the final changes.

Example 1 : to create a local file in Terraform

to create a resource in HCL( Hashicorp Configuration Language ) we use the following code block.

resource "local_file" "pet" {
    filename = "/root/pets.txt"
    content = "We love pets!"
}

# description of the code block
--------------------------------
# resource_argument : Description
---------------------------------
# resource : block type
# "local_file" : Resource type
# "pet" : Resource Name
# filename : file path where file has to be created
# content : content which needs to be written in that file

Example 2 : to create an EC2 instance on AWS cloud

to create ec2 instance using Terraform we can use below code.

resource "aws_instance" "webserver" {
    ami = "ami-id"
    instance_type = "t2.micro"
}

# description of the code block
--------------------------------
# resource_argument : Description
---------------------------------
# resource : block type
# "aws_instance" : Resource type
# "webserver" : Resource Name
# ami : image id which will be used while creating the ec2 resource
# instance_type : type of instance which needs to be provisioned

Example 3 : to create S3 bucket on AWS cloud

to create s3 bucket using terraform on AWS Cloud we can use below code.

resource "aws_s3_bucket" "data" {
    bucket = "webserver-bucket-org-2207"
    acl = "private"
}

# description of the code block
--------------------------------
# resource_argument : Description
---------------------------------
# resource : block type
# "aws_s3_bucket" : Resource type
# "data" : Resource Name
# bucket : bucket name which will be assigned after resource has been created
# acl : type of access to private to given S3 bucket

Provider Versioning

During Terraform init, if version arguemnt is not specified, the most recent provider will be downloaded during init process.
For production use, we should constrain the acceptable version via configuration, to ensure that new version with breaking changes wont get automatically installed.
to specify specific version we use >=1.0 | <=1.0 | ~>2.0
by mentioning version terraform creates a lock file. which keeps the version mentioned in lock file.
to define version in code we use

terraform {
  required_providers {
    aws = {
      source = "hashicorp/aws"
      version = "~> 3.0"
    }
  }
}

provider "aws" {
  region = "us-east-1"
}

dependency lock file allows us to lock to a specific version of the provider
If a particular provider already has a selection recorded in the lock file, Terraform will always re-select that version for installation, even if a newer version has become available
we can override this behaviour by adding the -upgrade option when we run terraform init.

Terraform Refresh

terraform refresh command will check the latest state of your infrastructure and update the state file accordingly.
we don't run this commande explicity
this will be triggered automatically when we run terraform plan or terraform apply
this command is deprecated in newer versions of terraform

Authentication Configuration

from security point of view, we should not keep credentials in a terraform file.
we want our code to run successfully without hardcoding the secrets in the provider block.
how to add config files

provider "aws" {
  shared_config_files = ["/Users/tf_user/.aws/conf"]
  shared_credentials_files = ["/Users/tf_user/.aws/creds"]
  profile = "customprofile"
}

resource "aws_eip" "lb" {
  domain = "vpc"
}

if shared files config lines are not added to provider block, by default, terraform will locate files $HOME/.aws/config and $HOME/.aws/credentials on Linux and macOS.
best way to store aws credentials is to use aws cli.

Ansible for Beginners

Linux_guy — Sun, 25 Aug 2024 14:26:05 +0000

What is Ansible?

Ansible is a automation used to carry our repetitive task.
ex. of these can be following:

provisioning
Configuration Management
Continout Devlivery
Application Deployment
Security Compliance

Features of Ansible

Simple
Powerful
Agentless

Ansible configuration File

Default location on linux:

# configuration file default path on linux
/etc/ansible/ansible.cfg

Sections of Configuration file

[defaults]
# default location for inventory files
inventory   = /etc/ansible/hosts
log_path    = /var/log/ansible.log

library     = /usr/share/my_modules/
roles_path  = /etc/ansible/roles
action_plugins  = /usr/share/ansible/plugins/action

gathering  = /implicit

# SSH timeout 
timeout  = 10
forks  = 5

[inventory]

[privilege_escalation]

[paramiko_connection]

[colors]

How to override Default config file

in some complex scenarios we need to override current default config file path for different hosts.

# using Environment variable 
$ANSIBLE_CONFIG=/opt/ansible-web.cfg ansible-playbook playbook.yml

Priority to be used for configuration files

file path which is used in environment variables
directory where ansible paths are being running from
config file which are stored in users home directory
default Config file stored at default location

Scenario 2
If there is a case we have to store value value of specific ansible playbook
To achieve this we can set the specific Config variables for the specific ansible playbook

# using variable defination
ANSIBLE_GATHERING=explicit anisble-playbook playbook.yml

# using export method
export ANSIBLE_GATHERING=explicit
ansible-playbook playbook.yml

# by defining the variable in ansible config file
# path : /opt/web-playbooks/ansible.cfg
gathering  = explicit

How to check all the configuration for the file

# this command will list all the configuration
ansible-config list

# shows the current config file
ansible-config view

# shows the current settings
ansible-config dump

How to Write YAML

YAML Stands for Yet Another Markup Language
it's a scripting language used to created automation

Thing to learn about yaml

How to store information using Key value pair
How to create Arrays/List
How to create Dictionary/Map

How to create Key value pair

to create key value pair we use colon sign ex.

key : value

How to create Array/List

to create array we use hypen(-) in front of and element ex.

Fruits:
- Orange
- Apple
- Banana

Ansible Inventory

Ansible can manage multiple hosts, this is done using existing agents on the systems.
For linux -> SSH
for windows hosts -> Powershell Remoting

To store these Hosts information we use inventory file, if custom inventory file is not created then ansible uses default invetory file stored at

/etc/ansible/hosts

ansible supports 2 types of formats for inventory files:

INI format
YAML format

Let's look at the sample inventory file in INI format

# list of number of servers
serv1.company.com
serv2.company.com
serv3.company.com

# we can also group server by a common name
[mail]
mail_serv1.company.com
mail_serv2.company.com
mail_serv3.company.com

Inventory Parameters

to connect to a specific host we use can define multiple parameters.
like:

host alias
ansible connection type
ansible connection port
ansible user
ansible ssh password

example of ansible inventory parameters

web ansible_host=serv1.company.com ansible_connection=ssh ansible_user=root ansible_ssh_pass=root
window_host ansible_host=serv2.company.com ansible_connection=winrm ansible_user=administrator ansible_pass=admin

# to interact with local machine
localhost ansible_connections=localhost

Ansible Variables

variable are used to store information in ansible.to use variables in Ansible we use jinja 2 templating.
in this example all the codes and variables are defined in the same file.

example code

-
   name: Add DNS server to resolve.conf
   hosts: localhost
    vars:
       dns_server: 10.1.250.10
   tasks:
      - lineinfile:
          path: /etc/resolve.conf
          line: 'nameserver {{ dns_server }}'

to organise code in a better way we can define variables in separate file.
ex. variables file

http_port: 8081
snmp_port: 161-162
inter_ip_range: 192.0.2.0

example playbook file to use these variables

-
    name: Set firewall configuration 
    hosts: web
    tasks: 
    - firewalld:
         service: https
         permanent: true
         state: enabled
    - firewalld:
         port: '{{ http_port }}'/tcp
         permanent: true
         state: disabled
    - firewalld:
         port: '{{ snmp_port }}'/udp
         permanent: true
         state: disabled
    - firewalld:
         source: '{{ inter_ip_range }}'/24
         Zone: internal
         state: enabled

Variable Types

Number variables: which holds numeric values
Boolean variables: which holds boolean values
List variables: which holds list of items
Dictionary variables

Variable Precedence

when defining variables, some methods of defining variables takes higher precedence then others.
these precedence are defined from higher to lower given below:

Extra vars
play vars
Host vars
Group vars

Explanantion:

first ansible checks for the variables defined for a group, if there is a specific value defined for a specific hosts, then that value will overwrite the Groups Variables.
similarly variables defined at playbook level with overwrite the variables defined at host level.
at last variables defined with extra vars keywords will overwrite the playbook variables and have highest precedence.

Registering variables

in some scenarios we want to pass some variables to other commands, this can be done by using registering the variables and storing them.
ex. for the same

- shell: cat /etc/hosts
  register: results
- debug: 
    var: results

Note

Output of the variable depends on the type of module which has been used
another way to view output of the debug module is to use -v parameter while running the playbook ex.

ansible-playbook -i inventory playbook.yml -v

Variables Scope

scope defines the accessiblity and visiblity of a variable to elements in the code.
scope depends on the position how and where it has been defined in the given code

we'll talk about various types of scopes

1. Host scope

host scope is available in the play which is running for the given host

2. Play scope

play scope is available in while the current play is running

3. Global variables scope

scope of this variable is visible to all as it passed while running the playbook by the parameter knows as extra-vars ex.

ansible-playbook playbook.yml --extra-vars "ntp_server=10.1.1.1"

Magic Variables

magic variables are used to access the information of the other hosts.
list of mostly used magic variables:

hostvars : this return the parameters associated with given host
groups: this return list of hosts which comes under the specified group
group_names: this return all group names which are associate with specific host
inventory_hostname: this gives out the name configured in the inventory file for the given host

Ansible Playbooks

ansible playbooks are used to define what actions need to be performed
playbooks are YAML scripts which defines the instructions which are needed to be performed
tasks are the actions to be performed on the host ex. 1.1 execute a command 1.2 Run a script 1.3 Install a package 1.4 Shutdown/Restart a server

GIT for Beginners

Linux_guy — Wed, 24 Apr 2024 04:30:17 +0000

Hello Readers! welcome to this Git series of tutorials.

I'll divide this series into different topics, so please hang in there.

For the starting I'll start with basics!

What is a GIT

Git is a version Control Software which is used to maintain change history of a codebase.

What is a GitHub

GitHub is a online website which is used to store all these git commit histories.

Install Git

To install git on linux host we can use these following commands.
Note: Please refer to the official website if case of any errors!!

# for debian Destros
sudo apt update
sudo apt install git-all
# for RHEL Destros
sudo yum update
sudo yum install git-all

Confirm successful installation of the Git?

to ensure git is available on the local machine, we can check it's version by using the command!

git --version

How to initialize a Git repository on the local machine!!?

to instalize a git repository on the local machine.

Step 1 : navigate to the given directory
Step 2 : initialize the git repository

git init

Gitignore

sometimes there are certain files which we dont want to upload on remote repository. to make this happen, we need to add the name of that file into .gitignore file

echo <filename> >> .gitignore
git add .gitignore
git commit -m "Git ignore file added"

Manage Git branches

How to create a new branch?

branches contains sequence of commits in git.
we can create or delete as much as branch as we required.

To create new branch

# this command will create a new branch with given branch name
git branch <branch-name>
# this command will create a new branch and switch to that branch
git checkout -b <branch-name>

Rename a branch

to rename a branch in git, use the given command!

# first switch to the main branch
git checkout <branch-name>

# second use the following command to change the branch name
git branch -m <old-name> <new-name>

Delete a branch

to delete a branch first we need to switch to other branch reason being we can't delete currently active branch

# change to other branch for example master.
git checkout master
# then run the delete branch command
git branch -d <branch-name>

Watch the commit history

to watch the commit history we have git log command

git log

Add Email and name

to add email and username we use the following commands

# to add username we use the command
git config --global user.name "Full Name"
# to add email we use the command
git config --global user.email "Email"

Store git credentials in linux

to add git credentials we use credential.helper utility
Step 1:

git config --global credential.helper store

Step 2:

git add .
git commit -m "message"
git push origin master
# enter username & password
username : github_username
password : Personal-Access-Token

to get personal tokken from github
- go to user settings
- click on developer settings
- click on generate classic token
- select all the repo options and copy token in git CLI

Setup SSH keys

navigate to ssh directory in home
- cd ~/.ssh/
Create ssh keys
- For Legacy Systems:
- ssh-keygen -o -t rsa -C "Email@address"
- For modern systems which support ED25519 algorithm:
- ssh-keygen -t ed25519 -C "your_email@example.com"
add ssh key to ssh-agent
- eval "$(ssh-agent -s)"
- ssh-add ~/.ssh/<path>
copy ssh-key.pub file to github to access private repos
check ssh connection with git using this command
- ssh -T git@github.com

DEV Community: Linux_guy

Terraform with AWS

Basics of Firewall

Ports

Firewall

SSH Tutorial

Create ssh keys

Installing Locate Package

To install locate command follow the steps

Docker Basics

Table of Contents

END

DSA Using C++

Starting with Pointers

Code without Pointers

Code with Pointers

Python : OS Module Introduction

OS module

Bash Script using Python

What do we need? 📝

How to run a simple bash command using python 🎯

Output:

passing argument as a list 🔐

Output:

Redirecting output to a file ➡️📁

Output:

What if!! we get an error!! 😲

Output:

What if!! 🤔 we want to discard the error

Output:

Reading 📖 a file 📁

Output:

grep the contents of the file

Output:

⚠️ Advanced ⚠️ !! content here!

Grid Engine Commands

QSTAT Command

QSUB

Job Submission Script

QDEL

How to check for the list of the nodes

Working With Shell

What is a shell?

Types of shell in Linux

Linux Commands

Home directory

How to know the Home directory

Directory Management

How to know your current path

How to create & remove directories

How to list the content of a folder

How to create a chain of directories

How to navigate through directories

How to navigate folder directory in Linux

Relative path

Absolute path

PUSHD & POPD

Terraform Beginners Blog

To install Terraform

How to create a resource in Terraform

Resource blocks

Terraform Workflow

Example 1 : to create a local file in Terraform

Example 2 : to create an EC2 instance on AWS cloud

Example 3 : to create S3 bucket on AWS cloud

Provider Versioning

Terraform Refresh

Authentication Configuration

Ansible for Beginners

What is Ansible?

Features of Ansible

Ansible configuration File

How to override Default config file

Priority to be used for configuration files

How to check all the configuration for the file

How to Write YAML

Thing to learn about yaml

How to create Key value pair

How to create Array/List

Ansible Inventory