Who Stole Port 80?
nginx won't start because something has port 80. Find the squatter, evict it cleanly, and get nginx serving again.
Puzzle Overview
nginx is the intended web server on this host, but every time it starts it exits with "Address already in use." Something else grabbed port 80. Your job is to identify what's there, remove it properly (not just kill the PID), and bring nginx up.
Skills tested: process and socket inspection (ss, lsof), systemd service lifecycle, understanding why a "kill and restart" is not a real fix.
Technologies Covered
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