Articles
Explanations, step-by-step guides, cheat sheets and fixes. Pick an area, or tell us what you need.
What kind of help
What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
Area
Clear filters
112 entries match these filters
- 0156 Operators, the software catalog (OperatorHub) and OLM on OpenShift Operators automate installing and running software on OpenShift. Learn the difference between cluster Operators and add-on Operators, and how OLM uses catalogs,… Intermediate · Explains an idea · Linux Article Cluster administration · Concepts 15 Oct 2026
- 0164 systemd services: systemctl and journalctl basics systemd starts and supervises services on most Linux servers. systemctl starts, stops and enables them; journalctl shows their logs. Beginner · Explains an idea · Linux Article Services & systemd 15 Oct 2026
- 0122 PCA 3.x health monitoring and upgrade workflow overview How Private Cloud Appliance 3.x reports health (Grafana, Prometheus, Loki, platform health checks) and how appliance upgrades work: ISO images, an upgrade… Advanced · Explains an idea · Linux Article Administration & monitoring 15 Oct 2026
- 0123 KVM vs QEMU vs libvirt: how Linux virtualization fits together KVM is the Linux kernel part that uses CPU virtualization extensions, QEMU is the program that emulates a full machine around it,… Beginner · Explains an idea · Linux Article Basics 15 Oct 2026
- 0131 Kubernetes architecture: control plane, nodes, kubelet and etcd A Kubernetes cluster is a control plane that stores and decides the desired state, plus worker nodes that run your containers. This… Beginner · Explains an idea · Linux Article Concepts 15 Oct 2026
- 0132 Pods, ReplicaSets and Deployments explained A Pod runs one or more containers together, a ReplicaSet keeps a fixed number of identical Pods alive, and a Deployment manages… Beginner · Explains an idea · Linux Article Concepts · Workloads & services 15 Oct 2026
- 0133 Services and Ingress: exposing an app in Kubernetes A Service gives a changing set of Pods one stable address. ClusterIP is internal, NodePort and LoadBalancer reach outside, and an Ingress… Intermediate · Explains an idea · Linux Article Ingress & networking 15 Oct 2026
- 0134 ConfigMaps and Secrets: configuration outside the image ConfigMaps hold plain settings and Secrets hold sensitive values, injected into Pods as environment variables or files. Secrets are only base64-encoded, not… Intermediate · Explains an idea · Linux Article Config, secrets & storage 15 Oct 2026
- 0102 Proxmox VE storage types: local, LVM-thin, ZFS, NFS and Ceph Proxmox VE stores disks, ISOs, templates and backups in storage pools defined in /etc/pve/storage.cfg. Learn the main storage types, what local and… Intermediate · Explains an idea · Linux Article Disks, LVM & filesystems · Storage 15 Oct 2026
- 0105 High availability in Proxmox VE: HA resources, fencing and affinity rules Proxmox VE HA restarts VMs and containers on another node when a node fails. Learn the requirements, how watchdog fencing protects your… Advanced · Explains an idea · Linux Article Clusters & high availability 15 Oct 2026
- 0115 What is Oracle Private Cloud Appliance (PCA)? Hardware, enclaves and release lines Oracle Private Cloud Appliance is a factory-built rack of compute, storage and network hardware with its own cloud software. Release 3.x offers… Beginner · Explains an idea · Linux Article Architecture & concepts 15 Oct 2026
- 0116 PCA 3.x Compute Enclave concepts: tenancies, compartments, VCNs, instances, images and shapes The PCA 3.x Compute Enclave uses OCI building blocks: a tenancy holds compartments, which hold networks, instances and storage. Instances are built… Beginner · Explains an idea · Linux Article Architecture & concepts · Compute, networking & storage 15 Oct 2026
- 0068 SQL joins explained: INNER, LEFT and finding rows with no match A join combines rows from two tables using a matching condition. INNER JOIN keeps only matches, LEFT JOIN keeps every row from… Intermediate · Explains an idea · Any system Article Joins 15 Oct 2026
- 0069 NULL in SQL: why = NULL never matches and how to handle missing values NULL means "unknown", so comparisons with it are neither true nor false. Use IS NULL, COALESCE and careful aggregates to avoid rows… Intermediate · Explains an idea · Any system Article Queries 15 Oct 2026
- 0070 Indexes and EXPLAIN: making SQL queries fast An index is a sorted lookup structure that lets the database jump to matching rows instead of reading the whole table. EXPLAIN… Advanced · Explains an idea · Any system Article Indexes & performance 15 Oct 2026
- 0072 CSV vs JSON: choosing a format and avoiding the classic pitfalls CSV is a simple table of text; JSON holds nested, typed data. Both break in predictable ways: quoting, delimiters, encodings, numbers and… Beginner · Explains an idea · Any system Article CSV & JSON 15 Oct 2026
- 0081 How an HTTP request works: methods, headers, and body An HTTP request is a short text message a client sends to a server: a method and path, some headers, and sometimes… Beginner · Explains an idea · Any system Article Making requests 15 Oct 2026
- 0086 API authentication basics: API keys, Bearer tokens, and OAuth How APIs know who is calling: static API keys, Bearer tokens in the Authorization header, Basic auth, and a high-level tour of… Intermediate · Explains an idea · Any system Article Authentication 15 Oct 2026
- 0098 What Proxmox VE is: KVM virtual machines, LXC containers and a web UI Proxmox VE is an open source virtualization platform based on Debian. It runs KVM virtual machines and LXC containers and is managed… Beginner · Explains an idea · Linux Article Basics · Installation & first steps 15 Oct 2026
- 0049 Pipes and redirection: connecting commands A pipe sends one command's output into another command, and redirection sends output to a file. Together they let small tools build… Beginner · Explains an idea · Linux, macOS Article Basics · Text processing 15 Oct 2026
- 0050 File permissions: chmod, chown and what 755 means Every file has an owner, a group and read/write/execute permissions for three kinds of users. chmod changes the permissions and chown changes… Beginner · Explains an idea · Linux, macOS Article Basics 15 Oct 2026
- 0051 Environment variables and PATH Environment variables are named settings that every program inherits from the shell. PATH is the one that tells the shell where to… Beginner · Explains an idea · Linux, macOS Article Basics 15 Oct 2026
- 0055 Docker basics: images, containers and the commands you need An image is a read-only package of an app and its dependencies, and a container is a running instance of it. Learn… Beginner · Explains an idea · Linux, macOS, Windows Article Docker basics 15 Oct 2026
- 0035 Undoing changes in Git: restore, reset, revert, and reflog Pick the undo command by where the mistake lives: in a file, in the staging area, in a local commit, or in… Intermediate · Explains an idea · Any system Article Undoing changes 15 Oct 2026
- 0004 Logging instead of print The logging module gives every message a level, a timestamp and a destination you can change without editing code. It is the… Intermediate · Explains an idea · Any system Article Files & automation 15 Oct 2026
- 0005 Dataclasses in depth @dataclass writes __init__, __repr__ and __eq__ for classes that mainly hold data. Learn defaults, default_factory, frozen and ordered classes, __post_init__ validation, slots… Advanced · Explains an idea · Any system Article Basics 15 Oct 2026
- 0016 let, const and var: variables and scope in JavaScript Use const by default, let when a value must change, and avoid var. The difference is about scope: where a variable is… Beginner · Explains an idea · Any system Article Basics 15 Oct 2026
- 0018 Promises and async/await explained A promise is a placeholder for a value that arrives later. async/await lets you write code that waits for promises as if… Intermediate · Explains an idea · Any system Article Async code 15 Oct 2026
- 0024 TypeScript basics: types, interfaces, unions and narrowing TypeScript adds type annotations to JavaScript and checks them before your code runs. These are the core ideas you need to read… Beginner · Explains an idea · Any system Article Basics 15 Oct 2026
- 0033 The everyday Git workflow: status, add, commit, push, pull Git moves your changes through three places: the working folder, the staging area, and the commit history. These five commands, plus .gitignore… Beginner · Explains an idea · Any system Article Housekeeping · Setup 15 Oct 2026
- 0034 Merging vs rebasing in Git Merge and rebase both bring commits from one branch into another. Merge keeps history exactly as it happened; rebase replays your commits… Intermediate · Explains an idea · Any system Article Branching & rebasing 15 Oct 2026
- 0001 Virtual environments with venv A virtual environment is a private folder of Python packages for one project, so projects never fight over versions. Create one with… Beginner · Explains an idea · Any system Article Environments & packages 15 Oct 2026