https://my-it-blog.netlify.app/tags/debugging/ Recent content in Debugging on My IT Journal Hugo en-us Sun, 19 Apr 2026 00:00:00 +0000 https://my-it-blog.netlify.app/posts/log-analysis--system-debug/ Sun, 19 Apr 2026 00:00:00 +0000 https://my-it-blog.netlify.app/posts/log-analysis--system-debug/ <h1 id="-log-analysis--system-debugging-lab">🧪 Log Analysis &amp; System Debugging Lab</h1> <h2 id="-objective">📌 Objective</h2> <ul> <li>Read system logs like real incidents</li> <li>Identify root causes</li> <li>Debug common system failures</li> </ul> <hr> <h2 id="-environment">⚙️ Environment</h2> <ul> <li>OS: Ubuntu</li> <li>Tools: journalctl, df, du, dmesg</li> </ul> <hr> <h2 id="-scenario-1-service-crash-investigation">🚨 Scenario 1: Service Crash Investigation</h2> <h3 id="step-1---break-the-service">Step 1 - Break the service</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>sudo nano /etc/nginx/nginx.conf </span></span></code></pre></div><p>Add invalid line:</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>invalid_directive; </span></span></code></pre></div><p>Restart:</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>sudo systemctl restart nginx </span></span></code></pre></div><h3 id="step-2---investigate">Step 2 - Investigate</h3> <p>Check status:</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><img alt="Nginx" loading="lazy" src="https://my-it-blog.netlify.app/posts/log-analysis--system-debug/nginx.png"></p> <p><img alt="Failed" loading="lazy" src="https://my-it-blog.netlify.app/posts/log-analysis--system-debug/failed_nginx.png"></p> <p>Check logs:</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>sudo journalctl -u nginx -n <span style="color:#ae81ff">50</span> --no-pager </span></span></code></pre></div><p><img alt="Journal" loading="lazy" src="https://my-it-blog.netlify.app/posts/log-analysis--system-debug/journalctl.png"></p>