All posts
Red Hat Certified Engineer (RHCE) #9 Tags and conditionals: when, loop, until
The ninth post in the Red Hat Certified Engineer (RHCE) series. We organize the core tools that control the flow of a playbook — conditional execution with when, iteration with loop, retries with until, and partial runs with tags. We learn the exam-staple patterns hands-on: branching by OS, bulk-creating a user list, retrying while waiting for a service to come up, and using tags to run only the tasks you need.
Red Hat Certified System Administrator (RHCSA) #6: Local Storage 2 — LVM Expansion and LUKS Encryption
The sixth post in the Red Hat Certified System Administrator (RHCSA) series. We add a PV to a volume group and grow it with vgextend, enlarge the logical volume with lvextend, then extend the file system itself with xfs_growfs and resize2fs — and we build a LUKS-encrypted volume with cryptsetup, setting it up to unlock automatically at boot through crypttab and fstab. We also cover exam staples like XFS being impossible to shrink.
AWS Certified CloudOps Engineer - Associate (SOA-C03) #1 Exam Introduction — Exam Structure and Study Roadmap
The first post in the AWS Certified CloudOps Engineer - Associate (SOA-C03) series. It covers the rename from SysOps Administrator to CloudOps Engineer, the 65-question / 130-minute / 720-point structure, the weight of the five domains (Monitoring 22% , Reliability 22% , Deployment Automation 22% , Networking 18% , Security 16%), and a study strategy that turns the hands-on experience from the [AWS practical track](/en/posts/aws-basics-1-account-region-az), [SAA-C03](/en/posts/aws-saa-1), and [DVA-C02](/en/posts/aws-dva-1) into operational judgment. This 15-part series is designed to help you pass SOA-C03, and it ends with a full-scale mock exam in #15.
AWS Certified Developer - Associate (DVA-C02) #7 Domain 2-1 Security — Authentication and Authorization
The first post of the DVA-C02 security domain. From a developer's perspective, it revisits IAM Roles (instance profile, ECS task role, Lambda execution role), STS temporary credentials and AssumeRole/federation, and the division of roles between a Cognito User Pool (authentication) and an Identity Pool (temporary AWS credentials), all at the exam level. The security domain is the second-largest at 26%.
Build an Online Shop with Next.js #2: Product Catalog
Build the product list and detail pages with Server Components, add a category filter with searchParams, and cover next/image, generateStaticParams, and notFound in one pass.
Certified Kubernetes Administrator (CKA) #16 Storage 1: Volume Types, PV, PVC, and Static Provisioning
The sixteenth post in the Certified Kubernetes Administrator (CKA) series. From Volume types (emptyDir, hostPath, configMap/secret, PVC) to a PersistentVolume's capacity and accessModes, persistentVolumeReclaimPolicy, the request and binding rules of a PersistentVolumeClaim, and the static provisioning where an admin creates PVs ahead of time — all walked through with YAML examples.
Certified Kubernetes Application Developer (CKAD) #11 Probes: liveness, readiness, startup (exec/HTTP/TCP)
Part 11 of the Certified Kubernetes Application Developer (CKAD) series. Learn the three probes (liveness, readiness, startup) and the three handlers (exec, httpGet, tcpSocket) that Kubernetes uses to check whether a container is alive and ready to take traffic — through YAML examples — and nail down the liveness-vs-readiness distinction that trips people up most often on the exam.
Certified Kubernetes Security Specialist (CKS) #9: Pod Security Admission (PSA, Pod Security Standards)
The ninth post in the Certified Kubernetes Security Specialist (CKS) series. It covers how Pod Security Admission — the replacement for the retired PodSecurityPolicy — rejects dangerous Pods at the namespace level. We work through the three levels of the Pod Security Standards (privileged, baseline, restricted) and the three modes (enforce, audit, warn), applying them with namespace labels, the security settings restricted demands, and how to write a Pod that passes — all from an exam point of view.
How Are QR Codes and Barcodes Read? The Basics of Encoding
This post explains, without any code, how barcodes and QR codes hold information and get read by machines. It covers the numbers held in stripes and dots, clears up the misconception that a QR code holds the full content rather than just an address, and error correction, at a non-developer's level.
How Does Google Search Work? The Basics of Crawling, Indexing, and Ranking
This post explains, without any code, how Google returns millions of sorted results in under a second. It walks through the three stages — gathering pages by crawling, organizing them into an index, and deciding their order by ranking — at a non-developer's level.
Python Data Analysis #6 Visualization: matplotlib Fundamentals and Choosing Charts
The minimal matplotlib structure understood through Figure and Axes, fast plotting with DataFrame.plot, picking the right chart for each purpose, fixing broken fonts in CJK environments, and saving with savefig — the visualization fundamentals in one post.
Red Hat Certified Engineer (RHCE) #8 Error handling: block/rescue/always, failed_when, ignore_errors
The eighth post of the Red Hat Certified Engineer (RHCE) series. We cover the error handling that controls the flow when a playbook fails mid-run. From the exam point of view, we work through structuring exceptions with block/rescue/always, letting failures slide with ignore_errors, defining your own failure conditions with failed_when, and shoring up the idempotency of the command module with changed_when.