PHP & Web Development Blogs

Linux is an incredibly powerful operating system favored by developers, system administrators, and tech enthusiasts alike. Whether you're just starting your journey with Linux or looking to refresh your knowledge, understanding basic Linux commands is essential for navigating the command line interface (CLI) efficiently. In this beginner's guide, we'll introduce you to some fundamental Linux commands that will help you get started and feel more comfortable in the terminal.

Accessing the Terminal:

Before we dive into the commands, let's briefly discuss how to access the terminal on different Linux distributions:

-GNOME (Ubuntu, Fedora, Debian): Press Ctrl + Alt + T to open the terminal.

-KDE (Kubuntu): Press Alt + F2, type konsole, and press Enter.

-Command Line Interface (CLI) Only (Arch Linux, CentOS): You're already in the terminal!

Basic Navigation:

cd (Change Directory): Use cd followed by the name of the directory to navigate to that directory. For example:

cd Documents 

ls (List Files): Use ls to list the files and directories in the current directory.

ls 

pwd (Print Working Directory): Use pwd to display the full path of the current directory.

pwd 

File Management:

mkdir (Make Directory): Use mkdir followed by the name of the directory to create a new directory.

mkdir my_directory 

touch: Use touch followed by the name of the file to create a new empty file.

touch my_file.txt 

cp (Copy): Use cp followed by the source file and destination to copy files.

cp source_file.txt destination_directory/ 

mv (Move/Rename): Use mv followed by the source and destination to move or rename files.

mv old_name.txt new_name.txt 

rm (Remove): Use rm followed by the file name to delete files. Be careful as this action is irreversible.

rm unwanted_file.txt 

Working with Text:

cat (Concatenate): Use cat followed by the file name to display the contents of a file.

cat my_file.txt 

nano or vim (Text Editors): Use nano or vim followed by the file name to edit a file in the terminal.

nano my_file.txt 

grep (Global Regular Expression Print): Use grep followed by a search term and file name to search for a specific pattern in a file.

grep "pattern" my_file.txt 

System Information:

uname (Unix Name): Use uname to display system information.

uname -a 

df (Disk Free): Use df to display disk space usage.

df -h 

top or htop (Process Monitoring): Use top or htop to display real-time system resource usage.

top 

Conclusion:

Mastering basic Linux commands is the first step toward becoming proficient in using the Linux command line interface. In this guide, we've covered some essential commands for navigation, file management, working with text, and obtaining system information. As you continue to explore Linux, you'll discover a vast array of commands and utilities that can help you streamline your workflow and accomplish a wide range of tasks from the terminal. Happy command line exploring!

In today's digital age, where data breaches and cyber attacks are increasingly prevalent, safeguarding sensitive information is paramount. Cryptography, the art of secure communication, plays a crucial role in ensuring data confidentiality, integrity, and authenticity. Implementing cryptography in PHP, one of the most widely used server-side scripting languages, offers a robust means to protect your data. In this guide, we'll explore how to utilize cryptography effectively in PHP to enhance the security of your applications.

Understanding Cryptography Basics

Before diving into PHP implementations, it's essential to grasp the fundamental concepts of cryptography. At its core, cryptography involves techniques for encrypting plaintext data into ciphertext to conceal its meaning from unauthorized parties. Key aspects of cryptography include:
   
. Encryption: The process of converting plaintext data into ciphertext using an algorithm and a secret key. This ciphertext can only be decrypted back to its original form using the appropriate decryption key.
   
. Decryption: The reverse process of encryption, where ciphertext is transformed back into plaintext using the decryption algorithm and the correct key.
   
. Symmetric Encryption: A type of encryption where the same key is used for both encryption and decryption. Examples include AES (Advanced Encryption Standard) and DES (Data Encryption Standard).
   
. Asymmetric Encryption: Also known as public-key cryptography, it involves a pair of keys: a public key for encryption and a private key for decryption. RSA and ECC (Elliptic Curve Cryptography) are common asymmetric encryption algorithms.

Implementing Cryptography in PHP

PHP provides robust cryptographic functions through its OpenSSL and Mcrypt extensions, allowing developers to implement various encryption techniques easily. Here's a step-by-step guide on how to perform common cryptographic operations in PHP:

1. Symmetric Encryption

<?php
$encryptionKey = openssl_random_pseudo_bytes(32);

$plaintext = "Sensitive data to encrypt";
$ciphertext = openssl_encrypt($plaintext, 'aes-256-cbc', $encryptionKey, 0, $iv);

$decryptedText = openssl_decrypt($ciphertext, 'aes-256-cbc', $encryptionKey, 0, $iv);

echo $decryptedText;
?>

2. Asymmetric Encryption

<?php
$config = array(
 "digest_alg" => "sha512",
 "private_key_bits" => 4096,
 "private_key_type" => OPENSSL_KEYTYPE_RSA,
);
$keyPair = openssl_pkey_new($config);

openssl_pkey_export($keyPair, $privateKey);
$publicKey = openssl_pkey_get_details($keyPair)["key"];

$plaintext = "Confidential message";
openssl_public_encrypt($plaintext, $encrypted, $publicKey);

openssl_private_decrypt($encrypted, $decrypted, $privateKey);

echo $decrypted;
?>

Best Practices for Cryptography in PHP

While implementing cryptography in PHP, it's essential to adhere to best practices to ensure maximum security:
   
. Use Strong Algorithms: Always use widely recognized cryptographic algorithms like AES for symmetric encryption and RSA for asymmetric encryption.
   
. Key Management: Safeguard encryption keys carefully. Utilize secure key management practices, such as storing keys in secure vaults and rotating them regularly.
   
. Data Integrity: Implement mechanisms to verify data integrity, such as HMAC (Hash-based Message Authentication Code), to detect tampering attempts.
   
. Secure Communication: When transmitting encrypted data over networks, use secure protocols like HTTPS to prevent eavesdropping and man-in-the-middle attacks.
   
. Stay Updated: Keep PHP and cryptographic libraries up to date to patch any security vulnerabilities and ensure compatibility with the latest cryptographic standards.

By following these guidelines and leveraging the cryptographic capabilities of PHP, developers can strengthen the security posture of their applications and protect sensitive data from unauthorized access. Remember, effective cryptography is not just about encryption but also encompasses key management, integrity verification, and secure communication practices. With diligence and proper implementation, PHP can be a powerful tool for building secure and resilient systems in today's digital landscape.

Composer is the way that that PHP developers manage libraries and their dependencies. Previously, developers mainly stuck to existing frameworks. If you were a Symfony developer, you used Symfony and libraries built around it. You didn’t dare cross the line to Zend Framework. These days however, developers focus less on frameworks, and more on the libraries they need to build the project they are working on. This decoupling of projects from frameworks is largely possible because of Composer and the ecosystem that has built up around it.

Like PHP, Composer is easy to get started in, but complex enough to take time and practice to master. The Composer manual does a great job of getting you up and running quickly, but some of the commands are involved enough so that many developers miss some of their power because they simply don’t understand.

I’ve picked out five commands that every user of Composer should master. In each section I give you a little insight into the command, how it is used, when it is used and why this one is important.

1: Require

Sample:

$ composer require monolog/monolog

Require is the most common command that most developers will use when using Composer. In addition to the vendor/package, you can also specify a version number to load along with modifiers. For instance, if you want version 1.18.0 of monolog specifically and never want the update command to update this, you would use this command.

$ composer require monolog/monolog:1.18.0

This command will not grab the current version of monolog (currently 1.18.2) but will instead install the specific version 1.18.0.

If you always want the most recent version of monolog greater than 1.8.0 you can use the > modifier as shown in this command.

$ composer require monolog/monolog:>1.18.0

If you want the latest in patch in your current version but don’t want any minor updates that may introduce new features, you can specify that using the tilde.

$ composer require monolog/monolog:~1.18.0

The command above will install the latest version of monolog v1.18. Updates will never update beyond the latest 1.18 version.

If you want to stay current on your major version but never want to go above it you can indicate that with the caret.

$ composer require monolog/monolog:^1.18.0

The command above will install the latest version of monolog 1. Updates continue to update beyond 1.18, but will never update to version 2.

There are other options and flags for require, you can find the complete documentation of the command here.

2: Install a package globally

The most common use of Composer is to install and manage a library within a given project. There are however, times when you want to install a given library globally so that all of your projects can use it without you having to specifically require it in each project. Composer is up to the challenge with a modifier to the require command we discussed above, global. The most common use of this is when you are using Composer to manage packages like PHPUnit.

$ composer global require "phpunit/phpunit:^5.3.*"

The command above would install PHPUnit globally. It would also allow it to be updated throughout the 5.0.0 version because we specified ~5.3.* as the version number. You should be careful in installing packages globally. As long as you do not need different versions for different projects you are ok. However, should you start a project and want to use PHPUnit 6.0.0 (when it releases) but PHPUnit 6 breaks backwards compatibility with the PHPUnit 5.* version, you would have trouble. Either you would have to stay with PHPUnit 5 for your new project, or you would have to test all your projects to make sure that your Unit Tests work after upgrading to PHPUnit 6.

Globally installed projects are something to be thought through carefully. When in doubt, install the project locally.

3: Update a single library with Composer

One of the great powers of Composer is that developers can now easily keep their dependencies up-to-date. Not only that, as we discussed in tip #1, each developer can define exactly what “up-to-date” means for them. With this simple command, Composer will check all of your dependencies in a project and download/install the latest applicable versions.

$ composer update

What about those times when you know that a new version of a specific package has released and you want it, but nothing else updated. Composer has you covered here too.

$ composer update monolog/monolog

This command will ignore everything else, and only update the monolog package and it’s dependencies.

It’s great that you can update everything, but there are times when you know that updating one or more of your packages is going to break things in a way that you aren’t ready to deal with. Composer allows you the freedom to cherry-pick the packages that you want to update, and leave the rest for a later time.

4: Don’t install dev dependencies

In a lot of projects I am working on, I want to make sure that the libraries I download and install are working before I start working with them. To this end, many packages will include things like Unit Tests and documentation. This way I can run the unit Tests on my own to validate the package first. This is all fine and good, except when I don’t want them. There are times when I know the package well enough, or have used it enough, to not have to bother with any of that.

Many packages create a distribution package that does not contain tests or docs. (The League of Extraordinary Packages does this by default on all their packages.) If you specify the --prefer-dist flag, Composer will look for a distribution file and use it instead of pulling directly from github. Of course if you want want to make sure you get the full source and all the artifacts, you can use the --prefer-src flag.

5: Optimize your autoload

Regardless of whether you --prefer-dist or --prefer-source, when your package is incorporated into your project with require, it just adds it to the end of your autoloader. This isn’t always the best solution. Therefore Composer gives us the option to optimize the autoloader with the --optimize switch. Optimizing your autoloader converts your entire autoloader into classmaps. Instead of the autoloader having to use file_exists() to locate a file, Composer creates an array of file locations for each class. This can speed up your application by as much as 30%.

$ composer dump-autoload --optimize

The command above can be issued at any time to optimize your autoloader. It’s a good idea to execute this before moving your application into production.

$ composer require monolog/monolog:~1.18.0 -o

You can also use the optimize flag with the require command. Doing this every time you require a new package will keep your autoloader up-to-date. That having said, it’s still a good idea to get in the habit of using the first command as a safety net when you roll to production, just to make sure.

BONUS: Commit your composer.lock

After you have installed your first package with composer, you now have two files in the root of your project, composer.json and composer.lock. Of the two, composer.lock is the most important one. It contains detailed information about every package and version installed. When you issue a composer install in a directory with a composer.lock file, composer will install the exact same packages and versions. Therefore, by pulling a git repo on a production server will replicate the exact same packages in production that were installed in development. Of course the corollary of this is that you never want to commit your vendor/ directory. Since you can recreate it exactly, there is no need to store all of that code in your repo.

It is recommended that also commit your composer.json. When you check out your repo into production and do an install, composer will use the composer.lock instead of the composer.json when present. This means that your production environment is setup exactly like your development environment.

Hi Guys,
I am sharing you the simple steps by which you can broadcast the web push notifications to your subscriber. In this tutorial we are making a subscriber form and saving information using Ajax and PHP and then through a server side code returning response to current logged in user and showing notification to that user.
Following are the steps to build this system

1. Create a database, I am creating db with name 'web_notifications'

Creating subscribers and notifications tables using following sql statements

CREATE TABLE IF NOT EXISTS <code>subscribers</code> (
 <code>id</code> int(11) NOT NULL,
 <code>name</code> varchar(255) NOT NULL,
 <code>email</code> varchar(255) NOT NULL,
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>subscribers</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>subscribers</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;



CREATE TABLE IF NOT EXISTS <code>notifications</code> (
 <code>id</code> int(11) NOT NULL,
 <code>to_user</code> int(11) NOT NULL,
 <code>title</code> varchar(255) NOT NULL,
 <code>body</code> varchar(255) NOT NULL,
 <code>url</code> varchar(255) NOT NULL,
 <code>is_sent</code> int(11) NOT NULL DEFAULT '0',
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>notifications</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>notifications</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;

2. Now create a db_connect.php file with following code

<?php 
session_start();
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "web_notifications";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
 die("Connection failed: " . $conn->connect_error);
} 
?>

3. Create a cookies.js file to read and write browser cookies

function WriteCookie(key,content) {
 var now = new Date();
 now.setMonth( now.getMonth() + 1 ); 
 document.cookie = key+"=" + escape(content) + ";";
 document.cookie = "expires=" + now.toUTCString() + ";"
}

function ReadCookie(key) {
 var allcookies = document.cookie;
 cookiearray = allcookies.split(';');
 var CookieData=Array();
 for(var i=0; i<cookiearray.length; i++) {
 k = cookiearray[i].split('=')[0];
 v = cookiearray[i].split('=')[1];
 CookieData[k]=v;
 }
 return CookieData[key];
}

4. Create a ajax file to read and mark is_sent if any notification foun to be sent in database for that user. create file with name 'fetch_notifications.php' with following content

<?php require 'db_connect.php';

$sql = "SELECT id,title,body,url FROM notifications where to_user='".@$_GET['user_id']."' and is_sent='0' ";
$result = $conn->query($sql);

$data=array();
if ($result->num_rows > 0) {
 while($row = $result->fetch_assoc()) {
 $data[]=$row;

 $upd = "update notifications set is_sent='1' where id='".$row['id']."' ";
 $conn->query($upd);

 }
}

if(count($data)>0)
{
 $response=array("status"=>1,"notification"=>$data);
}
else
{
 $response=array("status"=>0,"error"=>"No new notification!");
}

echo json_encode($response);

$conn->close(); 
?>

5. Now code index.php to show subscriber form and on submit insert record into the subscriber table

<?php require 'db_connect.php'; ?>
<!DOCTYPE html>
<html>
<head>
 <title>Web Push Notification Demo</title>
 <script src="./cookies.js" type="text/javascript"></script>
 <link href="
<script src="
<script src="
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/all.css" integrity="sha384-lKuwvrZot6UHsBSfcMvOkWwlCMgc0TaWr+30HWe3a4ltaBwTZhyTEggF5tJv8tbt" crossorigin="anonymous">
<?php 
if(isset($_POST['subscribe_form']))
{
 $_SESSION['is_login']=0;
 $username=$conn->real_escape_string($_POST['username']);
 $useremail=$conn->real_escape_string($_POST['useremail']);


 $sql = "INSERT INTO subscribers set name='".$username."',email='".$useremail."' ";
 if ($conn->query($sql) === TRUE) {
 $_SESSION['is_login']=1;
 $_SESSION['Uid']= $conn->insert_id;
 $_SESSION['Uname']= $username;
 ?>
 <script type="text/javascript">
 WriteCookie("Uid","<?php echo $_SESSION['Uid']; ?>");
 </script> 
 <?php
 $msg="<p style='color:green'>You have subscribe for push notification succesfully :)</p>";
 } else {
 $msg="<p style='color:red'>Error in subscribing for notifications</p>";
 }


}

?>
<div class="container">
<?php 
if(isset($msg) && $msg!='')
{
 ?>
 <br>
 <div class="alert alert-info">
 <?php echo $msg; ?>
 </div>
 <?php
}

if(isset($_SESSION['is_login']) && $_SESSION['is_login']==1)
{
 ?>
 <h2>Welcome <?php echo $_SESSION['Uname']; ?></h2>
 <script type="text/javascript"> 

setInterval(function(){ 
 check_notification(); 
}, 10000);

function check_notification()
{ 
 var Uid=ReadCookie("Uid");
 if(Uid!==undefined)
 {
 $.ajax({url: "fetch_notifications.php?user_id="+Uid, success: function(result){ 
 var response=JSON.parse(result);
 if(response.status==1)
 {
 
 response=response.notifications;
 for (var i = response.length - 1; i >= 0; i--) {
 var url = response[i]['url'];
 var noti = new Notification(response[i]['title'], {
 icon: 'logo.png', body: response[i]['body'],
 });
 noti.onclick = function () {
 window.open(url); 
 noti.close(); 
 };
 
 };

 }
 else{
 console.log(response.error);

 }
 
 }

 }); 
 }
}

 
 </script>
 <?php
}
else
{
 ?>
 <h2 class="text-center">Subscribe for Notifications</h2>
 <div class="row justify-content-center">
 <div class="col-12 col-md-8 col-lg-6 pb-5">

 <div class="card border-primary rounded-0">
 <div class="card-header p-0">
 <div class="bg-info text-white text-center py-2">
 <h3><i class="fa fa-envelope"></i> Information</h3>
 <p class="m-0">provide your information</p>
 </div>
 </div>
 <div class="card-body p-3">
 <form method="post">
 <!--Body-->
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-user text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="username" name="username" placeholder="Input Your Name Here" required>
 </div>
 </div>
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-envelope text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="useremail" name="useremail" pattern="[^@\s]+@[^@\s]+\.[^@\s]+" title="Invalid email address" placeholder="[email protected]" required>
 </div>
 </div>

 <div class="text-center">
 <input type="submit" value="Subscribe" name="subscribe_form" class="btn btn-info btn-block rounded-0 py-2">
 </div>
 </form>
 </div>

 </div>
 


 </div>
 </div>
<?php }?>
</div>



</head>
<body>

</body>
</html>
<?php 
$conn->close(); 
?>

The frontend of your subscription page (index.php) should look like this:




Now we are ready to receive notification in frontend, but we still need to create an admin page from where we can send notification to subscriber(s).

6. Create a table for admin user

CREATE TABLE IF NOT EXISTS <code>admin</code> (
 <code>id</code> int(11) NOT NULL,
 <code>username</code> varchar(255) NOT NULL,
 <code>password</code> varchar(255) NOT NULL,
 <code>createdAt</code> timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE <code>admin</code> ADD PRIMARY KEY (<code>id</code>);

ALTER TABLE <code>admin</code> MODIFY <code>id</code> int(11) NOT NULL AUTO_INCREMENT;

INSERT INTO <code>web_notifications</code>.<code>admin</code> (<code>id</code>, <code>username</code>, <code>password</code>, <code>createdAt</code>) VALUES (NULL, 'admin', MD5('123456'), CURRENT_TIMESTAMP);

Following is the code for admin.php to add the notifications to subscriber(s) account also i have inserted following login credentials for admin in admin table:
username:admin
password:123456

7. Now put following code in admin.php

<?php require 'db_connect.php'; ?>
<!DOCTYPE html>
<html>
<head>
 <title>ADMIN PAGE</title> 
 <link href="
<script src="
<script src="
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.1.0/css/all.css" integrity="sha384-lKuwvrZot6UHsBSfcMvOkWwlCMgc0TaWr+30HWe3a4ltaBwTZhyTEggF5tJv8tbt" crossorigin="anonymous">
<?php 
if(isset($_POST['login']))
{
 $_SESSION['admin_login']=0;
 $username=$conn->real_escape_string($_POST['username']);
 $password=$conn->real_escape_string($_POST['password']);
 $sql = "SELECT * FROM admin where username='".$username."' and password='".md5($password)."' ";
 $result = $conn->query($sql);
 if ($result->num_rows > 0) {
 $_SESSION['admin_login']=1;
 $msg="<p style='color:green'>Admin Logged-in Successfully :)</p>";
 }
 else {
 $msg="<p style='color:red'>INVALID CREDENTIALS FOR ADMIN</p>";
 } 


}
if(isset($_POST['add_notification']))
{ 
 $title=$conn->real_escape_string($_POST['title']);
 $body=$conn->real_escape_string($_POST['body']);
 $url=$conn->real_escape_string($_POST['url']);
 $users=$_POST['users'];

 foreach ($users as $user_id) {
 $ins = "insert into notifications set to_user='".$user_id."' , title='".$title."', url='".$url."', body='".$body."' ";
 $conn->query($ins);
 }
 $msg="<p style='color:green'>Notification(s) added to subscribers account.</p>";
 
}

?>
<div class="container">
<?php 
if(isset($msg) && $msg!='')
{
 ?>
 <br>
 <div class="alert alert-info">
 <?php echo $msg; ?>
 </div>
 <?php
}

if(isset($_SESSION['admin_login']) && $_SESSION['admin_login']==1)
{
 ?>
 <h2>Welcome Admin, Send notification to Subscriber(s)</h2>

<form method="post">
 
 

<div class="form-group">
 <label for="sel1">Select Subscriber(s):</label>
 <select multiple="multiple" required="required" class="form-control" id="users" name="users[]">
 <?php
$sql = "SELECT id,name FROM subscribers";
$result = $conn->query($sql);

$data=array();
if ($result->num_rows > 0) {
 while($row = $result->fetch_assoc()) {
 echo "<option value='".$row['id']."'>".$row['name']."</option>";
 }
}
?>
 </select>
</div>

 <div class="form-group">
 <label for="email">Title</label>
 <input type="text" required class="form-control" placeholder="notification title here" name="title" id="title">
 </div>
 
 <div class="form-group">
 <label for="email">Message</label>
 <textarea required class="form-control" placeholder="notification message here" name="body" id="body"></textarea> 
 </div>

 <div class="form-group">
 <label for="email">Url</label>
 <input type="url" required class="form-control" placeholder="notification landing/click url here" name="url" id="url">
 </div>
 
 <input type="submit" class="btn btn-primary btn-block" name="add_notification" value="Submit" />

</form>


 <?php
}
else
{
 ?>
 <h2 class="text-center">ADMINISTRATOR</h2>
 <div class="row justify-content-center">
 <div class="col-12 col-md-8 col-lg-6 pb-5">

 <div class="card border-primary rounded-0">
 <div class="card-header p-0">
 <div class="bg-info text-white text-center py-2">
 <h3><i class="fa fa-envelope"></i> LOGIN</h3>
 <p class="m-0">provide admin login credentials</p>
 </div>
 </div>
 <div class="card-body p-3">
 <form method="post">
 <!--Body-->
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-user text-info"></i></div>
 </div>
 <input type="text" class="form-control" id="username" name="username" placeholder="Input username here" required>
 </div>
 </div>
 <div class="form-group">
 <div class="input-group mb-2">
 <div class="input-group-prepend">
 <div class="input-group-text"><i class="fa fa-key text-info"></i></div>
 </div>
 <input type="password" class="form-control" id="password" name="password" placeholder="your password here" required>
 </div>
 </div>

 <div class="text-center">
 <input type="submit" value="Login" name="login" class="btn btn-info btn-block rounded-0 py-2">
 </div>
 </form>
 </div>

 </div>
 


 </div>
 </div>
<?php }?>
</div>



</head>
<body>

</body>
</html>
<?php 
$conn->close(); 
?>

The admin page will ask login credentials first then it will look like following screenshot:



Now in your project if you open index.php you have a frontend where user will register themselves to receive notifications, and admin.php is your backend where you can send notifications to users or subscribers


If you face any problem in setup this small project please just let me know in the comments below, or by messaging me.

Today I am going write a blog on how to Monitor Memory and Disk custom metrics and creating alarm in Ubuntu.

To do this, we can use Amazon CloudWatch, which provides a flexible, scalable and reliable solution for monitoring our server.

Amazon Cloud Watch will allow us to collect the custom metrics from our applications that we will monitor to troubleshoot any issues, spot trends, and configure operational performance. CloudWatch functions display alarms, graphs, custom metrics data and including statistics.

Installing the Scripts

Before we start installing the scripts for monitoring, we should install all the dependent packages need to perform on Ubuntu.

First login to your AWS server, and from our terminal, install below packages

sudo apt-get update
sudo apt-get install unzip
sudo apt-get install libwww-perl libdatetime-perl

Now Install the Monitoring Scripts

Following are the steps to download and then unzip we need to configure the Cloud Watch Monitoring scripts on our server:
1. In the terminal, we need to change our directory and where we want to add our monitoring scripts.
2. Now run the below command and download the source:

curl https://aws-cloudwatch.s3.amazonaws.com/downloads/CloudWatchMonitoringScripts-1.2.2.zip -O

3. Now uncompress the currently downloaded sources using the following commands

unzip CloudWatchMonitoringScripts-1.2.2.zip && \

rm CloudWatchMonitoringScripts-1.2.2.zip && \

cd aws-scripts-mon

The directory will contain Perl scripts, because of the execution of these scripts only report memory run and disk space utilization metrics will run in our Ubuntu server.
Currently, our folder will contain the following files:
mon-get-instance-stats.pl - This Perl file is used to displaying the current utilization statistics reports for our AWS instance on which these file scripts will be executed.
mon-put-instance-data.pl - This Perl script file will be used for collecting the system metrics on our ubuntu server and which will send them to the Amazon Cloud Watch.
awscreds.template - This Perl script file will contain an example for AWS credentials keys and secret access key named with access key ID.
CloudWatchClient.pm - This Perl script file module will be used to simplify by calling Amazon Cloud Watch from using other scripts.
LICENSE.txt – This file contains the license details for Apache 2.0.
NOTICE.txt – This file contains will gives us information about Copyright notice.
4. For performing the Cloud Watch operations, we need to confirm that whether our scripts have corresponding permissions for the actions:

If we are associated with an IAM role with our EC2 Ubuntu instance, we need to verify that which will grant the permissions to perform the below-listed operations:

cloudwatch:GetMetricStatistics

cloudwatch:PutMetricData

ec2:DescribeTags

cloudwatch:ListMetrics

Now we need to copy the ‘awscreds.template’ file into ‘awscreds.conf’ by using the command below and which will update the file with details of the AWS credentials.

cp awscreds.template awscreds.conf

AWSAccessKeyId = my_access_key_id

AWSSecretKey = my_secret_access_key

Now we completed the configuration.

mon-put-instance-data.pl

This Perl script file will collect memory, disk space utilization data and swap the current system details and then it makes handling a remote call to Amazon Cloud Watch to reports details to the collected cloud watch data as a custom metrics.

We can perform a simple test run, by running the below without sending data to Amazon CloudWatch

./mon-put-instance-data.pl --mem-util --verify --verbose

Now we are going to set a cron for scheduling our metrics and we will send them to Amazon CloudWatch
1. Now we need to edit the crontab by using below command:

 crontab -e

2. Now we will update the file using the following query which will disk space utilization and report memory for particular paths to Amazon CloudWatch in every five minutes:

*/5 * * * * ~/STORAGE/cloudwatch/aws-scripts-mon/mon-put-instance-data.pl --mem-util --mem-avail --mem-used --disk-space-util --disk-space-avail --disk-space-used --disk-path=/ --disk-path=/STORAGE --from-cron

If there is an error, the scripts will write an error message in our system log.

Use of Options

--mem-used
The above command will collect the information about used memory and which will send the details of the reports in MBs into the MemoryUsed metrics. This will give us information about the metric counts memory allocated by applications and the OS as used.
--mem-util
The above command will collect the information about memory utilization in percentages and which will send the details of the Memory Utilization metrics and it will count the usage of the memory applications and the OS.
--disk-space-util
The above command will collect the information to collect the current utilized disk space and which will send the reports in percentages to the DiskSpaceUtilization for the metric and for the selected disks.
--mem-avail
The above command will collect the information about the available memory and which will send the reports in MBs to the MemoryAvailable metrics details. This is the metric counts memory allocated by the applications and the OS as used.
--disk-path=PATH
The above command will collect the information and will point out the which disk path to report disk space.
--disk-space-avail
The above command will collect the information about the available disk space and which will send the reports in GBs to the DiskSpaceAvailable metric for the selected disks.
--disk-space-used
The above command will collect the information about the disk space used and which will send the reports in GBs to the DiskSpaceUsed metric for the selected disks.

The PATH can specify to point or any of the files can be located on which are mounted point for the filesystem which needs to be reported.

If we want to points to the multiple disks, then specify both of the disks like below:

--disk-path=/ --disk-path=/home

Setting an Alarm for Custom Metrics

Before we are going to running our Perl Scripts, then we need to create an alarm that will be listed in our default metrics except for the custom metrics. You can see some default metrics are listed in below image:



Once we completed setting the cron, then the custom metrics will be located in Linux System Metrics.

Now we are going to creating the alarm for our custom metrics
1. We need to open the cloudwatch console panel at https://console.aws.amazon.com/cloudwatch/home
2. Now navigate to the navigation panel, we need to click on Alarm and we can Create Alarm.
3. This will open a popup which with the list of the CloudWatch metrics by category.
4. Now click on the Linux System Metrics . This will be listed out with custom metrics you can see in the below pictures






5. Now we need to select metric details and we need to click on the NEXT button. Now we need to navigate to Define Alarm step.



6. Now we need to define an Alarm with required fields

Now we need to enter the Alarm name for identifying them. Then we need to give a description of our alarm.

Next, we need to give the condition with the maximum limit of bytes count or percentage when it notifies the alarm. If the condition satisfies, then the alarm will start trigger.

We need to provide a piece of additional information about for our alarm.

We need to define what are the actions to be taken when our alarm changes it state.

We need to select or create a new topic with emails needed for sending notification about alarm state.
7. Finally, we need to choose the Create Alarm.

So its completed. Now the alarm is created for our selected custom metrics.

Finished!

Now the alarm will be listed out under the selected state in our AWS panel. Now we need to select an alarm from the list seen and we can see the details and history of our alarm.