AIDE (Advanced Intrusion Detection Environment) is an open-source file integrity monitoring tool that detects unauthorized changes to files on a Linux system. It creates a cryptographic baseline database of your file system and compares the current state against that baseline on every check, alerting you to any additions, deletions, or modifications. AIDE is recommended by […]
Security auditing is a critical practice for any Linux administrator responsible for maintaining compliant and hardened systems. Lynis is a free, open-source security auditing tool that performs deep system scans and produces actionable hardening recommendations. On RHEL 9, Lynis integrates seamlessly and covers hundreds of security controls across authentication, networking, storage, and more. This tutorial […]
containerd is a high-performance, industry-standard container runtime that implements the Open Container Initiative (OCI) specification. While Docker uses containerd internally as its core container lifecycle manager, containerd can also run standalone as a Kubernetes container runtime — this is the default runtime for most managed Kubernetes services (EKS, GKE, AKS) and the recommended runtime for […]
HashiCorp Packer is an open-source tool for creating identical machine images for multiple platforms from a single configuration source. Rather than manually configuring servers after deployment, Packer bakes your configuration — packages, users, services, certificates — directly into the image at build time, embodying the immutable infrastructure pattern. The resulting AMIs, OVA files, or container […]
Bacula is a mature, enterprise-grade open-source backup solution that manages backup, recovery, and data verification across heterogeneous networks. It uses a three-tier architecture — Director, Storage Daemon, and File Daemon — allowing centralised policy management with distributed storage targets. On RHEL 9, Bacula packages are available from the EPEL repository and integrate naturally with systemd. […]
Jupyter Notebook is an interactive computing environment that allows you to create documents containing live Python code, equations, visualisations, and explanatory text in a single file. Notebooks (.ipynb files) are the standard format for data exploration, machine learning experiments, scientific computing, and educational tutorials because they let you execute code in small cells, inspect results […]
Pacemaker is a high-availability cluster resource manager that, combined with the Corosync messaging layer, enables automatic failover of services between cluster nodes. When a node or service fails, Pacemaker detects the failure and restarts the affected resources on a surviving node, minimising downtime. This tutorial builds a two-node active/passive HA cluster on RHEL 9, configuring […]
Email authentication through DKIM, SPF, and DMARC is no longer optional — major providers like Gmail and Outlook reject or junk messages from servers that lack these records. DKIM (DomainKeys Identified Mail) adds a cryptographic signature to outgoing messages, SPF (Sender Policy Framework) publishes a DNS record declaring which servers may send mail for your […]
PHP hardening reduces the attack surface of web applications by restricting what PHP scripts can do at the interpreter level. A default PHP installation exposes powerful functions that can be abused by attackers who exploit code injection vulnerabilities: system(), exec(), and passthru() allow execution of arbitrary OS commands; file_get_contents() with allow_url_fopen can fetch remote files; […]
ArgoCD’s GitOps model for Kubernetes delivery moves beyond traditional push-based CI/CD (where a pipeline runs kubectl apply) to a pull-based reconciliation loop where ArgoCD continuously monitors Git repositories and automatically brings the cluster state into alignment with the declared desired state. For production organisations, ArgoCD’s most powerful features are: ApplicationSets (templated applications that generate multiple […]
