Computer NetworKING & System Administrator

  📌 Essential Docker Commands for Daily Operations & Deployment This is a practical checklist I follow for daily Docker operations , image management , and frontend deployment . 🔹 1. Daily Monitoring & Inspection View running processes inside a container docker top <container_name> Example: docker top inventory-frontend 🔹 2. Build Frontend Image (Artifact Creation) Build Docker image from frontend source docker build -t inventory-frontend:prod1 ./frontend This creates a versioned frontend image that can be reused across environments. 🔹 3. Save Image as Artifact (For Transfer / Backup) Export Docker image to a tar file docker save inventory-frontend:prod1 -o inventory-frontend-prod1.tar Useful for: Moving images between servers Offline deployments Audit backups 🔹 4. Load Image on Target Server Import image from tar file docker load < inventory-frontend-prod1.tar 🔹 5. Stop & Remove Existing Frontend Container Stop running container docker stop inventory-fr...

 Of course. You are looking at a standard  Nmap scan  of a  Windows Domain Controller . Blocking these ports will severely break or completely disable your  Active Directory  domain and related services. Clients will be unable to log in, access files, or use  domain resources .   Warning: Do not block these ports on a Domain Controller without a deep understanding of the consequences. These are not "default ports to be blocked"; they are core service ports required for the server to function.   A more secure approach is to control access to these ports rather than blocking them entirely.   Here is a breakdown of what each service does and the correct way to secure it.   ---     Understanding the Ports & The Secure Alternative to Blocking   Instead of blocking, you should implement Windows Firewall with Advanced Security to restrict which source IPs are allowed to connect to these services....

Docker Image Layers Breakdown: Layer 1: FROM node:24 dockerfile FROM node:16 What it provides: - Base operating system (usually Debian/Alpine Linux) - Node.js runtime environment - npm package manager - System libraries and dependencies --- Layer 2: RUN apt-get update dockerfile RUN apt-get update What it does: - Updates package repository indexes - Ensures latest package versions are available - Creates a new layer with updated package lists --- Layer 3: RUN npm install dockerfile RUN npm install ``` What it does: - Installs all dependencies from package.json - Downloads node_modules - Adds application dependencies to the image --- Layer 4: COPY . /app dockerfile COPY . /app ``` What it does: - Copies your application source code - Adds configuration files - Includes all your custom files into the image --- 🎯 Key Benefits of This Layering: Storage Efficiency: Container A (Node App)    Container B (Node App) ├── App Code              ├── Dif...

 Category 1: Basic Concepts & Fundamentals  1. What is Active Directory (AD)?    Answer : Active Directory is a directory service developed by Microsoft for Windows domain networks. It is a centralized database that stores information about network resources (users, computers, printers, etc.) and provides authentication and authorization services. Essentially, it's the "phone book" for your network that also acts as a security guard. 2. What is the difference between a Workgroup and a Domain?    Answer:         Workgroup: A peer-to-peer network where each computer has its own local user database. Authentication is decentralized. Suitable for very small networks (e.g., less than 10 computers). No central administration.         Domain: A client-server network where a central server (Domain Controller) manages security and authentication for all computers and users. Provides centraliz...

  Fixing Commvault SQL Error: [30:436] – Instance Validation Failed Due to Insufficient SQL Server Role When working with Commvault backup and recovery solutions , administrators may encounter SQL-related errors during configuration or job execution. One such common error is: Error Code: [ 30 : 436 ] Description: Instance validation failed: Insufficient SQL Server role . To configure the instance, the user must be a member of the SYSADMIN SQL server role . Source: commvault, Process: JobManager This error prevents Commvault from completing instance validation, which is critical for proper backup and restore operations. Let’s break down the cause and provide a step-by-step solution. Why Does This Error Occur? Commvault requires elevated permissions on the underlying Microsoft SQL Server instance it connects to. If the user account running the Commvault process (JobManager, services, or installer) does not belong to the SQL Server SYSADMIN role , the validation will fa...

 In centos 8 Cause: This issue can be caused when the system has RHEL (RedHat) repositories installed (generally by mistake) or by old, bad, extra yum plugins.     Resolution: To fix this issue follow the steps below:   1. In your preferred editor (vi, vim, nano, etc.) open the “subscription-manager.conf” file sudo nano /etc/yum/pluginconf.d/subscription-manager.conf     2. Inside the “subscription-manager.conf” file change enabled to 0 and save the file enabled=0     3. Lastly issue the “yum clean all” command yum clean all     Check once