Linux & System Administration

Guide image showing methods to check active network ports and open connections across systems: use netstat/ss/lsof on Unix, Resource Monitor or netstat on Windows, and firewall checks.

Illustration of systemctl commands: start, stop, restart, enable, disable, status, is-active; managing units and services on systemd Linux with command examples, service lifecycle.

Illustration of configuring UFW: enable firewall, allow SSH, allow ports/apps, set default deny incoming, enable logging, verify status and manage rules with commands via CLI tools.

Graphic showing cron concept: terminal with crontab lines, clock, calendar and gears representing scheduled, recurring automated jobs and system maintenance tasks run by cron. now.

Illustration of system cleanup: removing temporary files cache and old log files to free disk space, showing progress bar, file icons being deleted and increased available storage.

Illustration of safe package maintenance: backup, check changelogs, update package lists, test in staging, run upgrades with confirmations, verify services and restore if issues occur.!!

Combined vmstat and iostat view: CPU/memory usage, process/context switch rates, I/O throughput and latency, device queue lengths, per-disk activity, and bottleneck signs overview.

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Diagram of group and permission management on Ubuntu and CentOS: file ownership, chmod/chown, chgrp, usermod, groupadd, sudoers.d, ACLs, shared folders, role-based access controls.

Terminal showing commands to add and delete Linux users: useradd, deluser, userdel, passwd, sudo examples, sample output and notes on home creation and group setup with sudo tips..