RHEL 9

Common Problems 114423

RHEL 9 SELinux denies web application file access

🟡 Medium   ⏱ 5–30 min  Last verified: 4 October 2023 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors & Cross-Refs References & Further […]

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How to Deploy a Spring Boot Application on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Deploy a Spring Boot Application on RHEL 9

Spring Boot is the most widely used Java web framework, providing an opinionated, auto-configured platform for building standalone, production-ready applications. Spring Boot embeds an HTTP server (Tomcat, Jetty, or Undertow) directly in the application JAR, eliminating the need for a separate application server deployment. A Spring Boot application is packaged as an executable “fat JAR” […]

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How to Set Up a Highly Available Web Stack with Keepalived on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Set Up a Highly Available Web Stack with Keepalived on RHEL 9

Keepalived implements the Virtual Router Redundancy Protocol (VRRP) on Linux, allowing two or more servers to share a single virtual IP address (VIP). If the master server fails, the backup server automatically claims the VIP within seconds, providing high availability with no changes required on clients or DNS. On RHEL 9, Keepalived integrates cleanly with […]

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Common Problems 114520

Root Filesystem Full and LVM Needs Extension

🟡 Medium   ⏱ 5–30 min  Last verified: 22 September 2023 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors & Cross-Refs References & Further […]

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Common Problems 114502

RHEL 9 Journalctl Shows Disk Usage Growing Rapidly

🟡 Medium   ⏱ 5–30 min  Last verified: 19 September 2023 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors & Cross-Refs References & Further […]

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How to Encrypt Disk Partitions with LUKS on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Encrypt Disk Partitions with LUKS on RHEL 9

LUKS (Linux Unified Key Setup) is the standard disk encryption framework on Linux, providing transparent block-level encryption that protects data at rest even if physical media is stolen. On RHEL 9, LUKS is backed by the cryptsetup tool and integrates tightly with the kernel’s device mapper subsystem. This tutorial walks through encrypting a new disk […]

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How to Set Up Port Knocking for SSH on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Set Up Port Knocking for SSH on RHEL 9

Port knocking is a security technique that hides your SSH port from network scanners by keeping it firewalled until a specific sequence of connection attempts is made. On RHEL 9, combining knockd with nftables lets you expose SSH only to clients who know the secret knock sequence, dramatically reducing brute-force exposure. This tutorial walks through […]

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Common Problems 114504

Persistent Journals Not Saved Across Reboots

🟡 Medium   ⏱ 5–30 min  Last verified: 8 September 2023 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors & Cross-Refs References & Further […]

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How to Profile Application Performance with perf on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Profile Application Performance with perf on RHEL 9

The perf tool is the Linux kernel’s built-in performance analysis framework, capable of sampling CPU events, tracing system calls, counting hardware performance counters, and generating flame graphs — all without any changes to the application under test. On RHEL 9, perf integrates tightly with the kernel’s BPF and tracepoint subsystems, making it one of the […]

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Common Problems 114572

Firewalld Rich Rule Order Producing Unexpected Drops

🟡 Medium   ⏱ 5–30 min  Last verified: 31 August 2023 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors & Cross-Refs References & Further […]

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