Firewall

How to Configure firewalld Zones on SLES 16 — step-by-step SUSE Linux Enterprise 16 tutorial on Progressive Robot

How to Configure firewalld Zones on SLES 16

Introduction This tutorial covers How to Configure firewalld Zones on SLES 16 on SLES 16. SLES 16 (SUSE Linux Enterprise Server 16) is SUSE’s enterprise-grade Linux distribution. It uses the zypper package manager, AppArmor for mandatory access control, and systemctl for service management. Prerequisites Ensure your SLES 16 system is up to date: zypper refresh […]

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Common Problems 127094

CentOS Stream 10 – Common Problem 188 – Diagnosis and Fix

🟡 Medium   ⏱ 5–30 min  Last verified: 6 November 2025 Affected versions: CentOS Stream 10 📖 ~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 […]

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Common Problems 124168

Oracle Linux 10 – Postfix starts but mail remains deferred due to SELinux policy denial – Fix & Prevention

🟠 High   ⏱ 5–30 min  Last verified: 6 November 2025 Affected versions: Oracle Linux 10 📖 ~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 […]

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Common Problems 124094

Oracle Linux 10 – nftables rule order drops established traffic – Fix & Prevention

🟠 High   ⏱ 5–30 min  Last verified: 6 November 2025 Affected versions: Oracle Linux 10 📖 ~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 […]

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How to Secure Nginx with Let's Encrypt and Certbot on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Secure Nginx with Let’s Encrypt and Certbot on RHEL 9

HTTPS is no longer optional — browsers mark HTTP sites as “Not Secure”, search engines penalise them in rankings, and many modern browser APIs (service workers, geolocation, camera access) require a secure context. Let’s Encrypt provides free, automated, and trusted SSL/TLS certificates via the ACME protocol, and Certbot is the recommended ACME client that handles […]

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Common Problems 119586

Debian 13 Docker Network Bridge Conflict With Host Subnet

🟡 Medium   ⏱ 5–30 min  Last verified: 6 November 2025 📖 ~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 Switch Default Java with alternatives on RHEL 10 — step-by-step RHEL 10 tutorial on Progressive Robot

How to Switch Default Java with alternatives on RHEL 10

Introduction Setting up switch default java with alternatives on a RHEL 10 server is a common task for system administrators, DevOps engineers, and site reliability engineers. This guide explains how to Switch Default Java with alternatives on RHEL 10, with all the commands you need, the SELinux and firewalld considerations to keep in mind, and […]

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How to Configure Apache Virtual Hosts on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Configure Apache Virtual Hosts on RHEL 9

Apache virtual hosts are the mechanism by which a single Apache HTTP Server instance serves multiple websites, distinguishing between them using the ServerName directive and the incoming Host HTTP header. Name-based virtual hosting (the most common type) allows hundreds of domains to share a single IP address, with Apache routing each request to the correct […]

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Common Problems 119492

Debian 13 – nftables Rules Lost After Reboot – Persistence and Policy Fix

🟡 Medium   ⏱ 5–30 min  Last verified: 6 November 2025 Affected versions: Debian 13 (Trixie) 📖 ~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 […]

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How to Install Apache HTTP Server on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Install Apache HTTP Server on RHEL 9

Apache HTTP Server (httpd) is the most historically significant web server in the history of the internet, powering billions of websites since 1995. On RHEL 9, Apache is available as httpd from the AppStream repository and integrates with SELinux, firewalld, and systemd. Apache’s module architecture makes it highly extensible: mod_rewrite for URL manipulation, mod_ssl for […]

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