#Certification
187 posts
Red Hat Certified System Administrator (RHCSA) #13: SELinux in depth — contexts, booleans, troubleshooting (audit2allow)
The thirteenth post in the Red Hat Certified System Administrator (RHCSA) series. We cover switching SELinux between enforcing/permissive and making it permanent, the structure of file and process contexts and applying policy-correct labels with semanage fcontext and restorecon, the booleans you flip with getsebool and setsebool -P, how to open a non-standard port with semanage port, and the troubleshooting flow that traces denial logs with ausearch, sealert, and audit2allow to build policy. We work through the most common RHCSA situation by hand — a service blocked by SELinux.
AWS Certified CloudOps Engineer - Associate (SOA-C03) #8 Domain 3-2 Deployment: Systems Manager Operations Automation
The eighth post of the SOA-C03 series covers Systems Manager, the core tool of the deployment and automation domain. It covers how to manage config and secrets with Parameter Store, apply patches in bulk with Patch Manager, maintain a desired state with State Manager, connect securely without keys via Session Manager, and also covers Run Command and Automation.
AWS Certified Developer - Associate (DVA-C02) #14 Exam Tips and Frequently Missed Patterns
The post right before the wrap-up of the DVA-C02 series. It lays out time management for 65 questions in 130 minutes, how to filter answer choices with constraint keywords, handling multiple-response and BEST/MOST questions, the most frequently confused concept pairs in DVA (SQS vs SNS vs EventBridge, User Pool vs Identity Pool, Secrets Manager vs Parameter Store, etc.), a per-domain keyword→service quick mapping, and a just-before-the-exam checklist.
Certified Kubernetes Administrator (CKA) #23 Troubleshooting 2: Nodes and kubelet (NotReady, disk/memory pressure)
The twenty-third post in the Certified Kubernetes Administrator (CKA) series. We follow the diagnostic flow for a node that has dropped to NotReady from start to finish. We read conditions with k describe node, SSH into the node and narrow down the cause with systemctl status kubelet and journalctl -u kubelet, and fix a stopped kubelet, a stopped runtime, a full disk, and memory pressure symptom by symptom. We also cover how to isolate a problem node with cordon and drain.
Certified Kubernetes Application Developer (CKAD) #18 Services: ClusterIP, NodePort, LoadBalancer, ExternalName
The eighteenth post in the Certified Kubernetes Application Developer (CKAD) series. It covers the Service, the object that puts a stable entry point in front of a shifting set of Pods. We learn how selectors and labels pick Pods and how Endpoints are managed automatically, the differences between the four types ClusterIP, NodePort, LoadBalancer, and ExternalName, the distinction between port, targetPort, and nodePort, headless Services and cluster DNS, and finally debugging empty endpoints — all through YAML and kubectl.
Certified Kubernetes Security Specialist (CKS) #16 Admission control: OPA/Gatekeeper, Kyverno
The 16th post in the Certified Kubernetes Security Specialist (CKS) series. We start from how an admission controller intercepts API requests to validate and mutate them, then learn the difference between validating and mutating webhooks, OPA/Gatekeeper's ConstraintTemplate and Constraint with Rego policies, and Kyverno's YAML-based validate/mutate/generate policies through examples. We implement "no latest tag" and "trusted-registry only" in both tools, and wrap up the exam-favorite pattern of rejecting a violating manifest.
Kubernetes and Cloud Native Associate (KCNA) #7: Cloud Native Application Delivery (8%) — GitOps, CI/CD
The seventh post in the KCNA series. We cover the whole of Domain 5: the split between CI and CD and the pipeline stages, the four principles of GitOps (ArgoCD, Flux) and pull-based delivery, deployment strategies (rolling, blue-green, canary), manifest management with Helm and Kustomize, and the basics of supply chain security.
Red Hat Certified Engineer (RHCE) #15 RHCSA Automation 2: Services, chronyd, log
The fifteenth post in the Red Hat Certified Engineer (RHCE) series. We automate the manual RHCSA work of service management, time synchronization, and log configuration with Ansible. We lock down daemons through enable and start in one shot with the service/systemd module, configure NTP with the timesync system role or a chrony template plus a handler, schedule jobs with the cron and at modules, and apply journald persistent storage and tuned profiles through playbooks.
Red Hat Certified System Administrator (RHCSA) #12: firewalld and SSH key authentication
The twelfth post in the Red Hat Certified System Administrator (RHCSA) series. We type through firewalld's zone concept and how to permanently allow services and ports with firewall-cmd, rich rules and source-based zone assignment, then how to set up SSH key authentication with ssh-keygen and ssh-copy-id and get the authorized_keys permissions right. We zero in on the RHCSA staples — permanently allowing ports and services and configuring key authentication — and the trap of forgetting --permanent.
AWS Certified CloudOps Engineer - Associate (SOA-C03) #7 Domain 3-1 Deployment — CloudFormation in Depth and IaC
The seventh post of the SOA-C03 series covers CloudFormation, the first topic of the deployment and automation domain (22%). It covers the structure of stacks and templates, change sets and drift detection, stack policies and deletion protection, StackSets for deploying across multiple accounts and regions, and the relationship with other IaC tools such as CDK and Terraform.
AWS Certified Developer - Associate (DVA-C02) #13 Domain 4-2 Troubleshooting and Optimization — Optimization and Problem Solving
The second post of the DVA-C02 troubleshooting domain. It covers choosing caching layers (CloudFront,ElastiCache,DAX,API Gateway), Lambda performance tuning (the relationship between memory and CPU,cold starts,concurrency), handling DynamoDB throttling, and the error codes that frequently appear on the exam (429,502,504,ProvisionedThroughputExceededException, etc.) and how to read them. This is the final step of looking at metrics, narrowing down the cause, and fixing it.
Certified Kubernetes Administrator (CKA) #22 Troubleshooting 1: Pods and Apps (Pending, CrashLoop, ImagePull, OOM)
The largest domain on the CKA exam is Troubleshooting (30%). In this post we tackle the four most common Pod-level failures within that domain. We organize Pending, CrashLoopBackOff, ImagePullBackOff/ErrImagePull, and OOMKilled each from symptom to diagnosis to fix in a single flow, and we drill the order in which to read describe, events, and logs so you reach the root cause fast.