#linux
All articles tagged #linux — practical guides from production experience.
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66 posts tagged #linux · page 1 of 8
NGINX 502 Bad Gateway Under Load: Root Causes and Fixes
NGINX 502 errors under load are almost never a simple app crash. This guide covers the real root causes — connection backlog overflow, keepalive misconfiguration, ephemeral port exhaustion — with diagnostic commands and config fixes from production incidents.
Log Analysis for Security Investigations: Windows Event Logs and Web Server Access Logs
A practical guide to log analysis for security investigations — Windows Event Viewer, critical Event IDs, Apache access log parsing, and the Linux command-line tools that make manual log analysis fast and effective.
How to Trace Route in Linux: traceroute Examples
Use traceroute in Linux to diagnose network path issues — read hop output, interpret timeouts, use TCP mode to bypass firewalls, and identify where packets are being dropped.
Too Many Open Files Linux: Fix Guide
Fix 'too many open files' errors on Linux — increase file descriptor limits for processes and system-wide, diagnose FD leaks, and configure permanent limits for production services.
How to Test TCP Connection in Linux: nc, curl, telnet
Test TCP connections in Linux using nc, curl, telnet, and /dev/tcp — verify port reachability, measure response time, and debug connection failures with real examples.
systemctl Service Not Starting: Complete Fix Guide
Fix systemctl service not starting — diagnose failed units, read exit codes, resolve dependency errors, and fix the most common reasons a Linux service won't start.
systemctl Restart Service Not Working: Fix Guide
Fix systemctl restart not working — diagnose failed units, read journal logs, handle dependency failures, and resolve the most common systemd service restart failures.
SSH Connection Refused Linux: Fix Guide
Fix SSH connection refused on Linux — diagnose why SSH won't connect, check sshd service and firewall, recover from lockout, and harden SSH without breaking access.
How to Search Text in Files Linux: grep Examples
Search text in files in Linux with grep — recursive search, regex patterns, context lines, count matches, and real-world log investigation examples.