Articles

297 entries match these filters

• 0274 What is DNS? DNS is the internet's phone book: it turns names like example.com into the IP addresses computers actually use. Beginner · Explains an idea · Any system Article DNS, IP addresses & ports 15 Oct 2026
• 0275 What is an IP address? An IP address is the unique number that identifies a device on a network so data knows where to go. Beginner · Explains an idea · Any system Article DNS, IP addresses & ports 15 Oct 2026
• 0276 What is SSH? SSH is a secure way to open a command line on another computer over the network, with everything encrypted. Beginner · Explains an idea · Any system Article SSH 15 Oct 2026
• 0277 What is TLS? TLS is the encryption layer that puts the S in HTTPS, protecting data between your browser and a server. Beginner · Explains an idea · Any system Article TLS & certificates 15 Oct 2026
• 0278 What is a certificate? A certificate is a digital ID card that proves a website or server is genuine, issued by a trusted authority. Beginner · Explains an idea · Any system Article TLS & certificates 15 Oct 2026
• 0279 What is a reverse proxy? A reverse proxy is a server that sits in front of your apps, receives all requests and forwards them to the right… Beginner · Explains an idea · Any system Article Web servers & reverse proxies 15 Oct 2026
• 0280 What is a firewall? A firewall is a filter that decides which network connections are allowed in or out of a computer or network. Beginner · Explains an idea · Any system Article Firewalls 15 Oct 2026
• 0281 What is a package manager? A package manager is a tool that installs, updates and removes software for you and keeps track of what depends on what. Beginner · Explains an idea · Any system Article Packages & updates 15 Oct 2026
• 0261 Build a Python command-line to-do app: from empty folder to installable command Create a small to-do tool in Python with argparse and JSON storage, test it with pytest and package it with pyproject.toml so… Beginner · Guided project · Any system Article Environments & packages · Files & automation · Testing 15 Oct 2026
• 0262 Make your first pull request: Git and GitHub from first commit to merged change A complete beginner's path through Git and GitHub: set up Git, make commits, ignore files, use branches, push to GitHub, open a… Beginner · Guided project · Any system Article Branching & rebasing · Pull requests · Setup 15 Oct 2026
• 0263 Build a notes REST API with plain Node.js: CRUD, validation, status codes and CORS Write a small JSON API for notes using only Node.js built-ins: create, read, update and delete, input validation, correct HTTP status codes,… Intermediate · Guided project · Any system Article Making requests · Node.js · Status codes 15 Oct 2026
• 0265 Turn a one-liner into a robust bash script: strict mode, options, logging, traps, locking and a schedule Grow a find-and-gzip one-liner step by step into a dependable bash script with strict mode, getopts, usage text, logging, error traps, dry-run,… Intermediate · Guided project · Linux, macOS Article Services & systemd · Shell scripting 15 Oct 2026
• 0249 Set up and harden a fresh Linux server in one afternoon Take a new Ubuntu, Debian or Rocky/Alma server from first login to a safer baseline: sudo admin, SSH keys only, firewall, automatic… Beginner · Guided project · Linux Article Networking & firewalls · Packages & updates · Users, sudo & hardening 15 Oct 2026
• 0250 Containerize a Node.js app and run it with PostgreSQL using Docker Compose Package a small Node.js web app in a multi-stage Docker image, then run it next to PostgreSQL with Docker Compose, named volumes,… Intermediate · Guided project · Linux, macOS, Windows Article Docker basics · Docker Compose · PostgreSQL 15 Oct 2026
• 0251 Learn Kubernetes on your laptop with kind: from first cluster to Ingress Build a throwaway Kubernetes cluster in Docker with kind, deploy a web app with config, secrets and probes, scale it, roll out… Beginner · Guided project · Linux, macOS, Windows Article Concepts · Workloads & services 15 Oct 2026
• 0252 Package a web app as a Helm chart: create, test, install, upgrade and roll back Turn a small nginx web app into your own Helm chart, check it with lint and template, install it into a namespace,… Intermediate · Guided project · Any system Article Helm 15 Oct 2026
• 0232 mongosh cheat sheet: CRUD, indexes and explain() The mongosh commands you use every day: switching databases, inserting, querying, updating and deleting documents, creating indexes and checking a query plan… Beginner · Cheat sheet · Any system Article Basics 15 Oct 2026
• 0253 Take an app to production on OpenShift: S2I build, TLS Route, storage, autoscaling and network policy Build a small Python app from Git with Source-to-Image on OpenShift or OKD, then add an HTTPS Route, config and secrets, storage,… Intermediate · Guided project · Linux, macOS, Windows Article Concepts · Deploying applications 15 Oct 2026
• 0233 Turn on MongoDB authentication and create least-privilege users A fresh MongoDB install accepts connections without a password. Create a user administrator, enable authorization, then give each application and backup job… Intermediate · Step by step · Linux Article Administration · Security & access 15 Oct 2026
• 0254 Automate three servers with Ansible: roles, templates, Vault and safe dry runs Build a real Ansible project for two web servers and one database server: inventory groups, SSH keys, roles, templates, handlers, an encrypted… Intermediate · Guided project · Linux, macOS Article Ansible · Keys & config 15 Oct 2026
• 0235 Fix: MongoServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017 Your app or tool tried to reach MongoDB on port 27017 and nothing accepted the connection. Usually mongod is not running, crashed… Intermediate · Fixes an error · Linux, macOS, Windows Article Administration · Basics 15 Oct 2026
• 0255 Build a monitoring stack with Prometheus, node_exporter and Grafana on one Linux server Install Prometheus and node_exporter as systemd services, scrape and query host metrics with PromQL, then add Grafana with a dashboard and an… Intermediate · Guided project · Linux Article Prometheus & Grafana · Services & systemd 15 Oct 2026
• 0236 Redis data types and commands: a quick reference Redis stores values under keys, and each value has a type: string, hash, list, set, sorted set or stream. The essential commands… Beginner · Cheat sheet · Any system Article Basics 15 Oct 2026
• 0256 Manage infrastructure as code with Terraform: from first file to plans on pull requests Learn the full Terraform workflow without a cloud account: variables, a module, outputs, state, plan, apply and destroy, a backend for shared… Beginner · Guided project · Linux, macOS, Windows Article GitHub Actions · Terraform 15 Oct 2026
• 0238 Redis persistence and high availability: RDB, AOF, replicas and Sentinel Redis keeps data in memory and writes it to disk with RDB snapshots, an append-only file, or both. Replicas copy data to… Intermediate · Explains an idea · Linux Article Administration & persistence 15 Oct 2026
• 0257 Run PostgreSQL properly on a Linux server: install, lock down, back up, monitor and patch Set up PostgreSQL 18 from the official repository for one application: a dedicated role and database, SCRAM logins from one app server… Intermediate · Guided project · Linux Article Backup & restore · Install & connect · Roles & administration 15 Oct 2026
• 0239 Fix: (error) NOAUTH Authentication required. (and securing Redis with ACLs) Redis requires a login and your client sent a command without one. Pass the right user and password, and use the moment… Advanced · Fixes an error · Linux Article Administration & persistence · Security & access 15 Oct 2026
• 0258 Build a MySQL 8.4 source-replica pair with GTIDs and rehearse a manual failover Set up GTID replication between two MySQL 8.4 servers, provision the replica with the clone plugin, then stop the source, promote the… Advanced · Guided project · Linux Article Administration · Replication 15 Oct 2026
• 0240 Fix: MISCONF Redis is configured to save RDB snapshots, but it’s currently unable to persist to disk Redis blocks writes because its last background snapshot failed. Find the cause in the log (full disk, permissions, failed fork), fix it,… Intermediate · Fixes an error · Linux Article Administration & persistence 15 Oct 2026
• 0259 Speed up a slow database query with a Redis cache: cache-aside in Python, measured and locked down Put Redis in front of a slow query in a small Python app: cache-aside reads, TTLs with jitter, invalidation on writes, an… Intermediate · Guided project · Linux Article Administration & persistence · Basics 15 Oct 2026
• 0241 Choosing a database: relational, document or key-value Relational databases, document stores like MongoDB and key-value stores like Redis each fit different jobs. An honest look at what each does… Beginner · Explains an idea · Any system Article Choosing a database · Database operations 15 Oct 2026
• 0260 Design and build a library database in SQLite: tables, keys, joins, reports and backups Model books, members and loans, create tables with keys and constraints, load sample data, write join and aggregate reports, add indexes checked… Beginner · Guided project · Any system Article Joins · Queries 15 Oct 2026
• 0242 Database security checklist: access, encryption, exposure and patching A practical checklist for hardening any database server, with MongoDB and Redis examples: no public exposure, authentication, least privilege, TLS, protected backups,… Advanced · Step by step · Linux Article Database operations · Security & access 15 Oct 2026
• 0243 Database backup strategy: the 3-2-1 rule and testing restores Keep three copies of your data on two kinds of storage with one copy offsite, choose dump or snapshot methods per database,… Intermediate · Step by step · Linux Article Database operations · Security & access 15 Oct 2026
• 0247 Build a Proxmox VE home lab: from bare metal to your first restored backup Install Proxmox VE on one spare machine, switch to the free update repository, create a VM and an LXC container, then schedule… Beginner · Guided project · Linux Article Backup & restore · Installation & first steps · VMs & containers 15 Oct 2026
• 0248 Run your first KVM virtual machine with libvirt and virt-install Turn a Linux desktop or server into a KVM host: check CPU support, install libvirt, use the default NAT network, create a… Beginner · Guided project · Linux Article Basics 15 Oct 2026
• 0201 pg_hba.conf and PostgreSQL authentication methods pg_hba.conf decides who may connect from where and how they must prove who they are. Rules are checked top to bottom and… Intermediate · Explains an idea · Linux Article Install & connect · Security & access 15 Oct 2026
• 0225 Oracle Data Pump: export and import schemas with expdp and impdp Data Pump moves schemas, tables or whole databases between Oracle databases as dump files. Set up a directory object, export with expdp… Intermediate · Step by step · Linux, Windows Article Administration · Backup with RMAN 15 Oct 2026
• 0202 Back up and restore PostgreSQL with pg_dump, pg_restore and pg_dumpall Make logical backups of one database with pg_dump, of roles and the whole cluster with pg_dumpall, and restore them with pg_restore or… Beginner · Step by step · Linux Article Backup & restore 15 Oct 2026
• 0226 Fix: ORA-12541: TNS:no listener The client reached the host but nothing was listening on that port. Start or fix the Oracle listener, or correct the host… Intermediate · Fixes an error · Linux, Windows Article Administration · Concepts & tools 15 Oct 2026