4 Systems & infrastructure
Every entry filed under Systems & infrastructure and its subtopics.
What kind of help
Works on
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- 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.
238 entries
- 0193 Linux logs reference: journalctl, journald storage, logrotate and centralized logging Read and filter systemd journal logs, keep their disk use in check, rotate classic log files with logrotate, and understand when to… Intermediate · Cheat sheet · Linux Article Linux administration · Logs 15 Oct 2026
- 0169 Add a new disk: partition, format and mount it by UUID Find a new disk with lsblk, partition it with parted, create an ext4 or XFS filesystem and mount it permanently through /etc/fstab… Intermediate · Step by step · Linux Article Disks, LVM & filesystems 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
- 0170 LVM explained: physical volumes, volume groups and logical volumes LVM puts a flexible layer between disks and filesystems, so you can grow volumes, add disks and take snapshots without repartitioning. Intermediate · Explains an idea · Linux Article Disks, LVM & filesystems 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
- 0188 First Terraform configuration: variables, a module and outputs (no cloud needed) A complete Terraform project that writes local files with the hashicorp/local provider, so you can practice init, plan, apply, modules and destroy… Intermediate · Step by step · Any system Script Terraform 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
- 0139 Collect describe, events and logs of a failing Kubernetes pod A bash script that saves a pod's status, describe output, events, YAML, current and previous logs of every container and its node… Intermediate · Step by step · Linux, macOS Script Troubleshooting 15 Oct 2026
- 0158 Collect an OpenShift project report with oc A read-only bash script that gathers a project's workloads, pods, routes, builds, storage and warning events, plus describe output and logs of… Intermediate · Step by step · Linux, macOS Script Deploying applications · Troubleshooting 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
- 0146 kubernetes/kubernetes The main source repository of Kubernetes: the API server, scheduler, controller manager, kubelet, kube-proxy and kubectl, plus release notes and issue tracking. Linux Repo Concepts 15 Oct 2026
- 0141 List Kubernetes pods that are not Running and Ready A bash script that lists every pod across namespaces that is Pending, failing or running but not ready, with the waiting reason,… Intermediate · Cheat sheet · Linux, macOS Script Troubleshooting 15 Oct 2026
- 0163 openshift/oc: the OpenShift command line client Source code of oc, the OpenShift CLI. It is built on top of kubectl, so it can do everything kubectl does, and… Any system Repo Cluster administration · Deploying applications 15 Oct 2026
- 0165 Write a systemd service unit for your own app Turn any long-running program into a proper service: create a unit file, run it as an unprivileged user, restart it on failure… Intermediate · Step by step · Linux Article Services & systemd 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
- 0142 Fix: ImagePullBackOff and ErrImagePull in Kubernetes The pod cannot start because the node failed to pull the container image. Read the "Failed to pull image" event to see… Intermediate · Fixes an error · Linux Article Troubleshooting 15 Oct 2026
- 0159 OpenShift cluster health snapshot: oc adm, nodes, MachineConfigPools and updates An admin overview of OpenShift day-2 checks (cluster version, update channels, cluster Operators, nodes, MachineConfigPools, must-gather) with a read-only bash script that… Advanced · Cheat sheet · Linux, macOS Script Cluster administration · Troubleshooting 15 Oct 2026
- 0166 Replace a cron job with a systemd timer A systemd timer runs a service on a schedule like cron, but logs every run to the journal, can catch up missed… Intermediate · Step by step · Linux Article Services & systemd 15 Oct 2026
- 0143 Fix: CrashLoopBackOff in Kubernetes The container starts, exits, and Kubernetes waits longer before each restart. Read the previous container's logs and its exit code to find… Intermediate · Fixes an error · Linux Article Troubleshooting 15 Oct 2026
- 0161 Fix: Error from server (Forbidden): … is forbidden: User … cannot … in OpenShift oc refuses a command with Error from server (Forbidden). The message names the user, verb, resource and project. Learn how to read… Intermediate · Fixes an error · Any system Article Cluster administration · Troubleshooting 15 Oct 2026
- 0167 Fix: Job for nginx.service failed because the control process exited with error code systemctl prints this when a service's start command exits with an error. The real reason is in journalctl; for nginx it is… Intermediate · Fixes an error · Linux Article Networking & firewalls · Services & systemd 15 Oct 2026
- 0148 derailed/k9s K9s is a terminal UI for Kubernetes that lets you browse resources, read logs, open shells and follow cluster changes from the… Any system Repo Troubleshooting 15 Oct 2026
- 0160 Fix: Permission denied in a container on OpenShift because of the random UID A container that works under Docker or Kubernetes crashes on OpenShift with permission denied, because restricted-v2 runs it with a random non-root… Advanced · Fixes an error · Linux Article Troubleshooting 15 Oct 2026
- 0137 Helm basics: install a chart, override values, upgrade and roll back Helm installs packaged Kubernetes apps called charts. Learn to add a repository, install a release, customize it with values files, upgrade it… Intermediate · Step by step · Any system Article Helm 15 Oct 2026
- 0147 helm/helm The Helm package manager for Kubernetes: the helm CLI and Go SDK for installing, upgrading and rolling back charts. Any system Repo Helm 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
- 0136 Persistent storage in Kubernetes: PersistentVolumes, claims and StorageClasses How to give a Pod storage that survives restarts: request it with a PersistentVolumeClaim, let a StorageClass provision it, and mount it.… Intermediate · Step by step · Linux Article Config, secrets & storage · Workloads & services 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
- 0144 Fix: Pod stuck in Pending with “0/3 nodes are available: Insufficient cpu” The scheduler cannot find a node with enough unreserved CPU for the pod's request. Compare the request with node allocatable resources, then… Advanced · Fixes an error · Linux Article Troubleshooting · Workloads & services 15 Oct 2026
- 0155 Security Context Constraints (SCC) and why root containers fail on OpenShift SCCs decide which user ID, capabilities and volumes a pod may use. Learn how restricted-v2 assigns random UIDs, how to see which… Advanced · Explains an idea · Linux Article Cluster administration · Concepts 15 Oct 2026
- 0145 Fix: OOMKilled (exit code 137) in Kubernetes A container used more memory than its limit and the kernel killed it. Confirm the reason, measure real usage, then raise the… Advanced · Fixes an error · Linux Article Troubleshooting · Workloads & services 15 Oct 2026
- 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
- 0162 okd-project/okd: the OKD community distribution Home of OKD, the community distribution of Kubernetes that powers Red Hat OpenShift. Releases of the installer and client, issue tracking and… Linux Repo Concepts 15 Oct 2026
- 0154 OpenShift app configuration: environment, ConfigMaps, Secrets and persistent storage Set environment variables, load ConfigMaps and Secrets into a Deployment as variables or files, and give it persistent storage with a PersistentVolumeClaim,… Intermediate · Step by step · Any system Article Config, secrets & storage · 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
- 0152 Build and deploy from source with oc new-app and Source-to-Image How oc new-app turns a Git repository or an image into a running app, how Source-to-Image and Docker builds are chosen, and… Intermediate · Step by step · Any system Article Deploying applications 15 Oct 2026
- 0138 Kubernetes RBAC basics: least-privilege access for a service account RBAC controls who may do what in a cluster with Roles, ClusterRoles and bindings. This guide grants a CI service account deploy… Advanced · Step by step · Linux Article Concepts · Config, secrets & storage 15 Oct 2026
- 0153 Expose apps with OpenShift Routes: edge, passthrough and re-encrypt TLS A Route publishes a service on a host name through the OpenShift router. Learn when to use plain HTTP, edge, passthrough or… Intermediate · Step by step · Any system Article Deploying applications · Ingress & networking 15 Oct 2026
- 0157 oc cheat sheet: everyday OpenShift CLI commands The oc commands you use every day, grouped by task: login and projects, apps and builds, routes, config, debugging, permissions and admin… Intermediate · Cheat sheet · Any system Article Deploying applications · Troubleshooting 15 Oct 2026
- 0108 List all Proxmox VE guests with status and locks (pvesh + jq) A Bash script that lists every VM and container in the cluster with node, status, lock, memory and uptime, using the Proxmox… Intermediate · Cheat sheet · Linux Script Shell scripting · VMs & containers 15 Oct 2026