Three tier architecture

 

Sudo su -                                   --> going to the root user for mysql installation.

dnf install mysql-server -y      --> here 'dnf' is the package manager 'mysql-server' is package. 'y'                                                             means we are saying yes to install.

systemctl enable mysqld        --> here 'd' means daemon, we call it daemon because they run                                                                             continuously in the background

 systemctl start mysqld

 systemctl status mysqld

netstat -lntp                --> to check if the port is open '3306' or not

ps -ef | grep mysql        --> to check the process is running

mysql -h <ipaddress> -u <username> -p<password> 

mysql  --> just give mysql to connect to the server when client is on the same machine.

default user name for mysql admin is root during installation.

mysql_secure_installation --set-root-pass Expense@App1  --> set password to root user

Show databases;            --> to show the list of databases

use mysql; --> to select which Schema to use

show tables;

select * from user;


NodeJs:

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Dependencies to install node.js is nginx, git etc.

build file = package.json --> where you mention your project metadata like name,description,version

build tool = npm --> it will search package.json in your folder and it will 

get the dependencies/libraries from internet.

Source files = .js


Sudo su -

dnf module list node.js --> here 'module' is in one OS it operats multiple versions

                            we can enable which version is required and disable which version is not required

dnf module disable nodejs:18 -y     --> this disables the 18 version of NodeJS

dnf module enable nodejs:20 -y    --> this enables the 20 version of Nodejs

dnf install nodejs  -y        --> Now Nodejs 20 version will install.

mkdir /app --> to place the project

curl -o /temp/backend.zip https://expense-builds.s3.us-east-1.amazonaws.com/expense-backend-v2.zip   --> Download the application code to created app directory.

cd /app

unzip /tmp/backend.zip

Cat package.json

npm install --> it checks for the package.json in thje folder and it downloads the listed

packages from from internet.

--> Now node_modules new folder is created 

/etc/systemd/system --> here you can place all your service files



In Linux logs are located at

var/log/messages

less /var/log/messages    --> here less is same like vim.

Java:

-----------

build file = pom.xml --> where we store Project name description, dependencies

build tool = maven --> it will search for pom.xml file in your folder and it will get the dependencies/libraties from internet

Source file = .java

For Python:

---------------------

build file = requirements.txt 

Build tool = pip --> it will search for the requirements.txt file and 

it will get the dependencies/libraries from internet

source file = .py












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