DevOps Core Guides
Deep, production-focused guides covering the technologies, commands, practices, and platforms modern DevOps engineers use every day. A small, curated collection of cornerstone references — written for engineers, reviewed for accuracy, and linked into the tools and error library you already use.
Engineering Fundamentals
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Git Commands
Every Git command a DevOps engineer needs, organized by workflow — with copyable examples and clear risk labels for the destructive ones.
Reference · Tutorial · Troubleshooting Read -
Linux Commands
A searchable Linux command reference for engineers — files, text, storage, processes, networking, services and troubleshooting, with Ubuntu-first examples.
Reference · Cheat sheet Read -
Bash Scripting
Write production-safe Bash: strict mode, error handling, traps, argument parsing and real automation templates you can drop into a pipeline.
Tutorial · Templates Read -
System Design
System design for engineers who operate what they build — scalability, availability, data, queues and failure modes, framed around real production architecture.
Concepts · Architecture Read
Delivery & Automation
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GitHub Actions
A complete CI/CD guide to GitHub Actions — workflow architecture, runners, secrets, OIDC, matrices, caching and production deployment patterns that actually hold up.
Guide · Production examples Read -
Docker Compose
Docker Compose from services to production — networks, volumes, health checks, secrets, profiles and complete sample stacks you can run and adapt.
Guide · Production stacks Read -
DevOps Practices
The practices that define modern delivery — IaC, CI/CD, GitOps, observability, SRE, progressive delivery — with when to use each, and when not to.
Strategy · Reference Read
Cloud & Security
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Cloud Security
Cloud security for DevOps — the shared responsibility model, IAM and least privilege, secrets, encryption, network segmentation, and supply-chain defense.
Guide · Checklists Read -
Kubernetes Security
Harden Kubernetes for production — RBAC, Pod Security Standards, NetworkPolicy, admission control and runtime security, with secure vs. insecure YAML side by side.
Hardening guide Read
Fix a whole class of errors
Where the Core Guides teach a subject, these hubs cluster the related error guides for one failure class — each with a paste-your-error assistant and every guide interlinked.
- Troubleshooting hub 13 guides
Kubernetes Storage & Volume Errors
Fix Kubernetes storage failures — PVC not bound, multi-attach, FailedMount, CSI deadline exceeded, and volume node-affinity conflicts — with worked diagnostics and copy-paste commands.
- Troubleshooting hub 13 guides
Kubernetes Pod Startup & CrashLoop Errors
Fix pods that will not start — CrashLoopBackOff, ImagePullBackOff, OOMKilled, CreateContainerConfigError, Init container failures and evictions — with root-cause diagnostics and commands.
- Troubleshooting hub 10 guides
Microsoft Entra ID (Azure AD) Sign-in Errors
Resolve Microsoft Entra ID / Azure AD AADSTS sign-in failures — conditional access blocks, consent required, invalid client secret, and token errors — across Teams and Azure apps.
- Troubleshooting hub 14 guides
Linux Disk, Mount & Filesystem Errors
Fix Linux storage failures — no space left on device, disk full, failed mounts, bad superblock, read-only filesystems, fstab boot failures, and umount target is busy — with exact commands.
- Troubleshooting hub 19 guides
OpenStack Nova Compute & Scheduling Errors
Fix OpenStack Nova failures — No valid host was found, instance failed to spawn, no allocation candidates, live-migration and placement errors — with the exact nova and placement commands.
- Troubleshooting hub 13 guides
OpenStack Neutron Networking Errors
Fix OpenStack Neutron failures — port binding failed, VIF plugging timeout, no more IP addresses, floating IP pool not found, dead OVS/DHCP/L3 agents — with the exact neutron and ovs commands.
- Troubleshooting hub 10 guides
OpenStack Cinder Block Storage Errors
Fix OpenStack Cinder failures — no weighed backends, volume stuck creating or in error, image unacceptable, backup failures, LVM/Ceph backend errors — with the exact cinder commands.
- Troubleshooting hub 50 guides
Kafka Broker, KRaft & Cluster Errors
Fix Kafka broker and cluster failures — KafkaServer startup errors, controller not available, inconsistent cluster ID, partition offline, log/storage and KRaft/ZooKeeper metadata errors — with exact commands.
- Troubleshooting hub 45 guides
Kafka Producer, Consumer & Client Errors
Fix Kafka client failures — producer timeouts, commit-failed and rebalance-in-progress, offset out of range, serialization and record-too-large errors, coordinator and auth failures — with exact fixes.
- Troubleshooting hub 49 guides
Docker Build & Image Errors
Fix Docker build and image failures — failed to solve with frontend dockerfile.v0, pull access denied, Docker Hub rate limits, cache-key and layer errors, manifest and platform mismatches — with exact fixes.
- Troubleshooting hub 69 guides
Docker Container & Runtime Errors
Fix Docker runtime failures — cannot connect to the Docker daemon, OCI runtime create failed, exec format error, port already allocated, volume/mount and permission errors — with exact commands.
- Troubleshooting hub 20 guides
Kubernetes Networking, DNS & Ingress Errors
Fix Kubernetes networking failures — connection refused in-cluster, CoreDNS SERVFAIL, dial tcp i/o timeout, no endpoints available, ingress 503/413, and CNI setup errors — with exact kubectl commands.
- Troubleshooting hub 49 guides
Ansible Playbook & Module Errors
Fix Ansible failures — could not get apt lock, couldn't resolve module/action, undefined variable, host key verification failed, become/privilege escalation, vault and Jinja2 template errors — with exact fixes.
- Troubleshooting hub 32 guides
RabbitMQ Connection, Channel & Auth Errors
Fix RabbitMQ connection and channel failures — ECONNREFUSED on 5672, ACCESS_REFUSED logins, TLS handshake failures, missed heartbeats, frame and protocol errors, blocked connections, and too-many-channels — with the exact rabbitmqctl and openssl commands.
- Troubleshooting hub 64 guides
RabbitMQ Cluster, Queue & Resource Errors
Fix RabbitMQ cluster and queue failures — Mnesia network partitions, quorum queues that lose majority, nodes that will not rejoin, memory/disk high-watermark alarms, flow control, unroutable messages, and stuck consumers — with exact rabbitmqctl and rabbitmq-diagnostics commands.
- Troubleshooting hub 150 guides
Log Shipping & Observability Pipeline Errors
Fix log-shipping and observability-pipeline failures across Filebeat, Logstash, and Loki — registry and harvester problems, pipeline and grok parse failures, ingester and object-store errors, backpressure, and dropped events — with the exact config checks and commands.
- Troubleshooting hub 50 guides
PostgreSQL Database Errors
Fix common PostgreSQL errors — duplicate key violates unique constraint, permission denied for table, relation does not exist, deadlock detected, and connection failures — with worked diagnostics and copy-paste SQL.
- Troubleshooting hub 50 guides
MySQL Database Errors
Fix common MySQL errors — ERROR 1064 syntax, 1045 access denied, 1040/1203 too many connections, 1062 duplicate entry, lock wait timeouts, and foreign-key failures — with worked diagnostics and copy-paste SQL.