Articles

167 entries match these filters

• 0172 Fix: No space left on device Writes fail because a filesystem is full, out of inodes, or holding space for deleted files that are still open. Find which… Beginner · Fixes an error · Linux Article Disks, LVM & filesystems 15 Oct 2026
• 0174 Network and DNS troubleshooting commands: ip, ss, dig, resolvectl A layer-by-layer cheat sheet for "the server cannot reach X": interfaces and routes with ip, listening ports with ss, and name resolution… Beginner · Cheat sheet · Linux Article Networking & firewalls 15 Oct 2026
• 0176 apt vs dnf: package commands and automatic security updates The everyday package commands on Debian/Ubuntu (apt) and RHEL/Rocky/Alma (dnf) side by side, plus how to turn on automatic security updates on… Beginner · Cheat sheet · Linux Article Packages & updates 15 Oct 2026
• 0177 Users, groups and sudo on Debian, Ubuntu and RHEL How Linux accounts and groups work, how to create users, and how sudo gives admin rights through the sudo group on Debian/Ubuntu… Beginner · Explains an idea · Linux Article Users, sudo & hardening 15 Oct 2026
• 0181 Ansible concepts: inventory, modules, playbooks, idempotency and roles Ansible configures many servers over SSH from one control machine. Learn the core pieces: inventory, modules, tasks, playbooks, roles, and why runs… Beginner · Explains an idea · Linux, macOS Article Ansible 15 Oct 2026
• 0187 Terraform concepts: providers, state, plan and apply, modules, and OpenTofu Terraform describes infrastructure in code, compares it with what exists, and changes only the difference. Learn providers, resources, state, the plan/apply loop,… Beginner · Explains an idea · Any system Article Terraform 15 Oct 2026
• 0198 Install PostgreSQL and connect with psql on Debian, Ubuntu and RHEL Install the PostgreSQL server from your distribution or the official PGDG repositories, start it, and open your first psql session as the… Beginner · Step by step · Linux Article Install & connect 15 Oct 2026
• 0135 Deploy your first app on Kubernetes A step-by-step tutorial: write a Deployment and a Service in YAML, apply them, reach the app, add health probes, roll out a… Beginner · Step by step · Linux Article Ingress & networking · Workloads & services 15 Oct 2026
• 0140 kubectl cheat sheet: the commands you use every day A compact reference of everyday kubectl commands: contexts and namespaces, listing and inspecting objects, logs and exec, applying changes, rollouts, scaling and… Beginner · Cheat sheet · Any system Article Concepts · Troubleshooting 15 Oct 2026
• 0149 OpenShift vs Kubernetes vs OKD: what OpenShift adds OpenShift is Red Hat's Kubernetes platform and OKD is its community distribution. Both add projects, routes, builds, image streams, Operators and stricter… Beginner · Explains an idea · Linux Article Concepts · Concepts 15 Oct 2026
• 0150 Logging in with oc and working with OpenShift projects Install the oc client, log in with a password, browser or token, then create, switch and inspect projects. Covers where oc stores… Beginner · Step by step · Any system Article Concepts · Deploying applications 15 Oct 2026
• 0151 Tutorial: deploy a small web app on OpenShift and expose it with a Route A step-by-step first deployment: create a project, build a static website from Git with Source-to-Image, publish it on an HTTPS Route, then… Beginner · Step by step · Any system Article Deploying applications 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
• 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
• 0101 Create LXC containers with pct and pveam Download a container template with pveam, create an unprivileged LXC container with pct, give it a network address and get a shell… Beginner · Step by step · Linux Article VMs & containers 15 Oct 2026
• 0110 Fix: TASK ERROR: VM is locked (backup) A VM or container still carries a backup lock, usually after a backup was interrupted. Check that no backup is running, then… Beginner · Fixes an error · Linux Article Backup & restore · VMs & containers 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
• 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
• 0073 Fix: json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0) Python's json module found nothing it could parse at the very first character. The input is usually empty, HTML, or already consumed.… Beginner · Fixes an error · Any system Article Common errors · 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
• 0082 HTTP status codes: the common ones and what to do A quick reference to the HTTP status codes you will meet most often, what each one means, and the first thing to… Beginner · Cheat sheet · Any system Article References · Status codes 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
• 0099 Proxmox VE repositories and updates: enterprise vs no-subscription A fresh Proxmox VE install uses the enterprise repository, which needs a subscription. Learn how to switch to the no-subscription repository and… Beginner · Step by step · Linux Article Installation & first steps · Packages & updates 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
• 0053 Set up SSH keys: ssh-keygen, ssh-copy-id and ~/.ssh/config SSH keys let you log in to servers and push to Git hosts without typing a password. Create an ed25519 key, install… Beginner · Step by step · Linux, macOS, Windows Article Keys & config 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
• 0057 Shell cheat sheet: everyday commands A quick reference for moving around, managing files, viewing and searching text, checking processes and disk space in bash and zsh, with… Beginner · Cheat sheet · Linux, macOS Article Basics · Command-line tools 15 Oct 2026
• 0067 Your first SQL queries: SELECT, WHERE, ORDER BY, LIMIT and GROUP BY Read data from a table, keep only the rows you want, sort them, take the first few, and summarize groups with COUNT,… Beginner · Step by step · Any system Article Queries 15 Oct 2026
• 0037 Git cheat sheet The Git commands you reach for most, grouped by task and using the modern switch and restore forms. Copy, paste, and replace… Beginner · Cheat sheet · Any system Article Git 15 Oct 2026
• 0038 The pull request workflow on GitHub A pull request asks to merge your branch into another one, with review and automated checks in between. This is the whole… Beginner · Step by step · Any system Article Pull requests 15 Oct 2026
• 0040 Fix: error: failed to push some refs to … Git refused your push, usually because the remote branch has commits you do not have yet. Bring them in, combine them with… Beginner · Fixes an error · Any system Article Common errors 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
• 0007 Fix: ModuleNotFoundError: No module named ‘…’ Python cannot find a module you import. Usually the package was installed into a different interpreter or virtual environment than the one… Beginner · Fixes an error · Any system Article Common errors · Environments & packages 15 Oct 2026
• 0008 Fix: TypeError: ‘NoneType’ object is not subscriptable You used [ ] on a value that is None. Something you expected to return a list, dict or match returned nothing.… Beginner · Fixes an error · Any system Article Common errors 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
• 0017 JavaScript array methods cheat sheet: map, filter, reduce and friends A quick reference for the array methods you use every day, with what each one returns and whether it changes the original… Beginner · Cheat sheet · Any system Article Basics 15 Oct 2026