Find guides, tutorials, and documentation to help you get the most out of CubePath services.
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Find what is eating CPU on an Ubuntu server: read load average and steal time, pinpoint processes and threads with top, ps and pidstat, then limit them.
Find out what is using RAM on Ubuntu: read free correctly, rank processes by RSS and PSS, spot leaks and OOM kills, then add swap or cap a service's memory.
Fix a full disk on Ubuntu: find large directories and files with du, ncdu and find, clean logs, journal, apt, snap and Docker, and recover deleted open files.
Diagnose DNS problems on Ubuntu 24.04 with dig, host and nslookup: check the local resolver, compare authoritative answers, verify PTR and mail records.
Find out why email is not sending or arriving on a Postfix server on Ubuntu 24.04 by reading mail.log, the mail queue, SMTP error codes and DNS records.
Find the cause of a slow website on Ubuntu 24.04: measure TTFB with curl, check server resources, log Nginx request times, and profile PHP-FPM and MySQL.
Fix the most common MySQL 8.0 errors on Ubuntu 24.04: failed connections, access denied, too many connections, lock timeouts, full disks and crashed tables.
Diagnose and fix Permission denied errors on Ubuntu 24.04: read modes and ownership, trace the blocking directory with namei, and set web, SSH and ACL rights.
Learn what a zombie (defunct) process is, how to find it and its parent with ps and pstree, and how to clear it safely by fixing or restarting the parent.
Learn what Linux load average really measures, find out whether a high load comes from CPU, disk I/O or memory pressure, and fix the process behind it.
Diagnose an unresponsive Linux server with standard commands: test connectivity, get a shell, check CPU, memory, disk, services and logs, then fix the cause.
Diagnose SSH connection failures step by step: timeouts, refused connections, permission denied and host key errors, with client and server-side fixes.
Detect floods, SSH brute force, web scans and signs of compromise on an Ubuntu server with ss, tcpdump and journalctl, then block the source and respond.
