https://my-it-blog.netlify.app/tags/troubleshooting/ Recent content in Troubleshooting on My IT Journal Hugo en-us Tue, 05 May 2026 00:00:00 +0000 https://my-it-blog.netlify.app/posts/dns-server/ Tue, 05 May 2026 00:00:00 +0000 https://my-it-blog.netlify.app/posts/dns-server/ <h1 id="-dns-lab">🧪 DNS Lab</h1> <h2 id="-objective">📌 Objective</h2> <p>Understand DNS from a systems perpective</p> <hr> <h2 id="-environment">⚙️ Environment</h2> <ul> <li>Virtualization: VirtualBox</li> <li>OS: ( 1 DNS Server VM + 1 Client VM)</li> </ul> <hr> <h2 id="-lab-network-topology">🛠️ Lab Network Topology</h2> <h3 id="-phase-1--direct-dns-no-cache">🧩 Phase 1 — Direct DNS (No Cache)</h3> <p>Client VM -&gt; dnsmasq (192.168.10.10)</p> <p>Used for:</p> <ul> <li>Break #1 (Wrong DNS Server)</li> <li>Break #2 (Wrong DNS Record)</li> </ul> <hr> <h3 id="-phase-2--direct-dns-no-cache">🧩 Phase 2 — Direct DNS (No Cache)</h3> <p>Clint VM -&gt; systemd-resolved (127.0.0.53) [CACHE] -&gt; dnsmasq (192.168.10.10) [DNS SERVER]</p> https://my-it-blog.netlify.app/posts/process-management--resource-control/ Fri, 24 Apr 2026 00:00:00 +0000 https://my-it-blog.netlify.app/posts/process-management--resource-control/ <h1 id="-process-management--resource-control-lab">🧪 Process Management &amp; Resource Control Lab</h1> <h2 id="-objective">📌 Objective</h2> <p>Simulate and troubleshoot a real-world system slowdown caused by CPU saturation and memory exhaustion.</p> <hr> <h2 id="-environment">⚙️ Environment</h2> <ul> <li>Virtualization: VirtualBox</li> <li>OS: Ubuntu Server</li> </ul> <hr> <h2 id="-lab-setup">🛠️ Lab Setup</h2> <h3 id="step-1---create-cpu-load-script">Step 1 - Create CPU Load Script</h3> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>nano cpu_hog.sh </span></span><span style="display:flex;"><span>chmod +x cpu_hog.sh </span></span></code></pre></div><p><img alt="cpu_script" loading="lazy" src="https://my-it-blog.netlify.app/posts/process-management--resource-control/cpu_heavy_script.png"></p> <hr> <h3 id="step-2---create-memory-load-script-python">Step 2 - Create Memory Load Script (Python)</h3> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>nano mem_hog.py </span></span><span style="display:flex;"><span>chmod +x mem_hog.py </span></span></code></pre></div><p><img alt="py_script" loading="lazy" src="https://my-it-blog.netlify.app/posts/process-management--resource-control/mem_heavy_py_script.png"></p> <hr> <h2 id="-incident-simulation">🚨 Incident Simulation</h2> <h3 id="step-1---check-the-system-load-baseline">Step 1 - Check the System Load Baseline</h3> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>uptime </span></span></code></pre></div><p><img alt="Baseline" loading="lazy" src="https://my-it-blog.netlify.app/posts/process-management--resource-control/uptime_baseline.png"></p> https://my-it-blog.netlify.app/posts/dhcp-server/ Thu, 23 Apr 2026 00:00:00 +0000 https://my-it-blog.netlify.app/posts/dhcp-server/ <h1 id="-dhcp-lab">🧪 DHCP Lab</h1> <h2 id="-objective">📌 Objective</h2> <p>Understand how DHCP works in real network environment and how to debug common failure scenarios using a structured top-to-bottom approach.</p> <hr> <h2 id="-environment">⚙️ Environment</h2> <ul> <li>Virtualization: VirtualBox</li> <li>OS: Ubuntu Server (1 DHCP Server VM &amp; 2 Client VMs)</li> <li>Network mode: Internal Network + NAT (enp0s3 ignored for DHCP lab)</li> </ul> <hr> <h2 id="-network-setup">🛠️ Network Setup</h2> <h3 id="interfaces">Interfaces</h3> <p>DHCP Server</p> <ul> <li>enp0s8 -&gt; 192.168.10.10/24 (Lab network)</li> <li>enp0s3 -&gt; NAT</li> </ul> <p>Clients</p> <ul> <li>enp0s8 -&gt; DHCP assigned IPs</li> <li>enp0s3 -&gt; NAT (not used)</li> </ul> <hr> <h3 id="-network-configuration-netplan">⚙️ Network Configuration (Netplan)</h3> <p>Both server and clients are configured using Netplan, which defines interface behavior before DHCP starts.</p> https://my-it-blog.netlify.app/posts/network--service-connectivity/ Mon, 20 Apr 2026 00:00:00 +0000 https://my-it-blog.netlify.app/posts/network--service-connectivity/ <h1 id="-linux-networking-and-service-exposure-lab">🧪 Linux Networking and Service Exposure Lab</h1> <h2 id="-objective">📌 Objective</h2> <p>This lab simulates real-world Linux networking issues and teaches how to troubleshoot:</p> <ul> <li>Service availability</li> <li>Port listening</li> <li>Firewall behavior (UFW)</li> <li>Binding (&rsquo;localhost&rsquo; vs external access)</li> <li>Network-layer debugging</li> </ul> <hr> <h2 id="-environment">⚙️ Environment</h2> <ul> <li>OS: Ubuntu (VM + Bridged Adapter)</li> <li>Service: Nginx</li> <li>Tools: ss, curl, ufw, systemctl</li> <li>Host machine for external testing (Powershell)</li> </ul> <hr> <h2 id="-stage-1">🟢 Stage 1</h2> <p>Verify service:</p> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>systemctl status nginx </span></span></code></pre></div><p>Expected outcome: Active (running)</p> <p>Check listening ports:</p>