Upgrade and installation

sudo apt update
sudo apt upgrade -y
sudo apt install netcat


/usr or /home

/usr is where the user’s home directory is.

/usr/bin — This contains application that the user would install on the system.

/user/bin/strings — Where strings utility located. For more info on strings utility, please refer this link.


This is where the sudoers file is located. sudoers file contains the rules that users must follow when using the sudocommand.

When using sudo command, you can basically make the system to obey any commands that you write. Therefore, sometimes, it is really useful…

About Roles

Roles are groupings of privileges that you can use to create different levels of database access.

About Administrative Accounts

By default, when Oracle Database is installed, the following administrative accounts are automatically created:

  • SYS (Granted the DBA role)

Under the schema of SYS user, all base tables and views for the database data dictionary are stored, which are critical for the operation of Oracle database.

Ensure that most database users are never able to connect to Oracle Database with the SYS account.

  • SYSTEM (Granted the DBA role)

The SYSTEM user can create additional tables and views that display…

What does Azure App Service do?

Now, most of the websites have moving pieces like shopping carts that require a server to host these things and process them.

This is where Azure App Service comes in. It is basically a platform that allows us to write our backend codes, store them and deploy them.

What does Azure App Service mean to Developers?

It is a Platform as a Service (PaaS). The beauty of having a platform that a VM is that you can just focus on writing your codes, use the tools that you are familiar with without having to…

When to use INDEX function?

VLOOKUP function only allows you to look up a value based on single criteria.

To look up a value based on multiple criteria in separate columns, use this generic formula:

{=INDEX(return_range, MATCH(1, (criteria1=range1) * (criteria2=range2) * (…), 0))}


  • Return_range is the range from which to return a value.
  • Criteria1, criteria2, … are the conditions to be met.
  • Range1, range2, … are the ranges on which the corresponding criteria should be tested.

Important note!

This is an array formula and it must be completed with Ctrl + Shift + Enter. This will enclose your formula…

What is Base64 Encoding?

Since computer talks using binary (numbers), the American Standard Code for Information Interchange (ASCII) decided to map a number to every letter, creating a standard that all computers can follow.

The Base64 algorithm dissects the original data in text format and encodes them in uppercase (A-Z) English letters, lowercase (a-z) English letters, 0–10 digits, “+” and “/” characters.

Base64 Encoding Explained with Examples | OpenTechTips

At the end of a base64 ended, you might see one or more “=” characters for padding purpose.

Base64 Encoding Cheat Sheet

Devices in Azure AD can be managed using Mobile Device Management (MDM) tools like:

  • Microsoft Intune
  • Microsoft Endpoint Configuration Manager
  • Group Policy (hybrid Azure AD join)
  • Mobile Application Management (MAM) tools
  • Other third-party tools.

Before we can do that, we need to get the device registered or joined to Azure AD through the below options:

  • Azure AD registered

Devices that are Azure AD registered are typically personally owned or mobile devices, and are signed in with a personal Microsoft account or another local account.

  • Azure AD joined

Devices that are Azure AD joined are owned by an organization, and are…

Apply lock on the website

  "resources": [
"type": "Microsoft.Web/serverfarms",
"apiVersion": "2020-12-01",
"name": "[parameters('hostingPlanName')]",
"location": "[parameters('location')]",
"sku": {
"tier": "Free",
"name": "f1",
"capacity": 0
"properties": {
"targetWorkerCount": 1
"type": "Microsoft.Web/sites",
"apiVersion": "2020-12-01",
"name": "[variables('siteName')]",
"location": "[parameters('location')]",

Automating Azure Blob Storage access tiers

"rules": [
"name": "agingRule",
"enabled": true,
"type": "Lifecycle",
"definition": {
"filters": {…

Create a Virtual Network

  1. Create a resource group
az group create 
--name CreateVNetQS-rg
--location eastus

2. Create a virtual network

az network vnet create 
--name myVNet
--resource-group CreateVNetQS-rg
--subnet-name default

3. Create a virtual machine

az vm create 
--resource-group CreateVNetQS-rg
--name myVM1
--image UbuntuLTS
--public-ip-address myPublicIP-myVM1

Manage Azure disks with Azure PowerShell

  1. Create the initial configuration with New-AzDiskConfig.
$diskConfig = New-AzDiskConfig 
-Location "EastUS"
-CreateOption Empty
-DiskSizeGB 128

2. Create the data disk with the New-AzDisk command.

$dataDisk = New-AzDisk 
-ResourceGroupName "myResourceGroupDisk"
-DiskName "myDataDisk"
-Disk $diskConfig

3. Get the virtual machine that you want to add the data disk…

Types of Load Balancers

Standard Load Balancer:

  • Supports up to 1000 instances.
  • Backup pool endpoints could be any virtual machines or virtual machine scale sets in a single virtual network.

Basic Load Balancer:

  • Supports up to 300 instances.
  • Virtual machines in a single available set or virtual machine scale set.

Forward Traffic to Specific Port at Backend

NAPT-en — Port forwarding — Wikipedia

This can be done by creating an inbound NAT port-forwarding rule:

  • Name: Type MyNATRuleVM1.
  • Port: Type 4221.
  • Target virtual machine: Select MyVM1 from the drop-down.
  • Network IP Configuration: Select ipconfig1 from the drop-down.
  • Port mapping: Select Custom.
  • Target port: Type 3389.

Alternative to…

Before DNS

All devices that are connected to the Internet are identified by an IP address. But, it is not easy for people to remember thus host name is invented.

Before DNS system is invented, a computer can keep a simple text file called a “hosts file” on “C:\\windows\system32\drivers\etc” that mapped host names to IP addresses.

Understanding DNS — Beginners Guide to DNS (steves-internet-guide.com)

What is DNS?

The DNS system consists of many Domain Name Servers that resolves DNS query. The main DNS severs (root servers) are owned and managed by a variety of different organizations.

As an end user, we do not need to manage a DNS…

goay xuan hui

A food lover, a cyber security enthusiast, a musician and a traveller, so you will see a mix of different contents in my blog. ☺️

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