Automate Linux System Administration Tasks

Provides production-ready bash script templates across ten categories of Linux system administration: file backups (timestamped directory tar, rsync to a remote server, backup rotation keeping a max count, mysqldump database backup with gzip), system monitoring (CPU/disk usage threshold alerts, a CPU usage logger, a full system health check combining uptime, load average, memory, disk, and top processes), user management (idempotent user creation with useradd, a password-expiry report via chage), security scripts (an openssl rand-based password generator, AES-256-CBC file encryption and decryption via openssl enc), log analysis (grep-based error extraction, an Apache/web-server log analyzer summarizing top IPs, URLs, and status codes), network scripts (multi-host ping connectivity checks, website uptime checks via curl, network interface and routing info), automation (idempotent package installation checking dpkg -l first, crontab task scheduling, a service restart script using systemctl is-active), file operations (rsync directory sync with --delete, find -mtime cleanup of old files, folder-size reporting via du -sh), system information collection (hostname, OS, CPU, memory, disk, network, and logged-in-users report), and git/development helpers (multi-repo fetch-and-pull updater, remote script execution over SSH).

#!/bin/bash
threshold=90

# Monitor CPU usage and trigger alert if threshold exceeded
cpu_usage=$(top -bn1 | grep "Cpu(s)" | awk '{print $2}' | cut -d. -f1)

if [ "$cpu_usage" -gt "$threshold" ]; then
    echo "ALERT: High CPU usage detected: $cpu_usage%"
fi

Use these as starting-point templates for common sysadmin tasks - scheduled backups, resource monitoring, user or password auditing, log analysis, network health checks, and routine automation - on any bash-capable Linux/Unix system. The skill is explicit that its scripts are building blocks for security operations and penetration-testing environments as well as ordinary ops work, and it comes with hard constraints: test in non-production first, use absolute paths, quote variables to handle spaces, and expect many scripts to need root or sudo. It is not a monitoring platform or a scheduler itself - the monitoring scripts print alerts to stdout and leave notification wiring like email or Slack as a comment to fill in, and scheduling is left to crontab.

Inputs are the paths, thresholds, hostnames, and credentials each script's variables expect: a backup source and destination pair, a CPU or disk percentage threshold, a database name and credentials, a list of hosts or websites, a package list, or a git repo list. Outputs are timestamped artifacts and reports: .tar.gz/.sql.gz backup files, .txt health-check and system-info reports, an .enc encrypted file or its decrypted counterpart, and log-derived reports like top-10 IPs and URLs plus an HTTP status-code distribution from a web server access log. A quick-reference table covers common bash patterns (${var:-default}, $(date +%Y%m%d), "$@") and the five-field cron schedule format.

Relies only on standard Linux/Unix tooling already present or installable via a package manager: rsync for file sync and remote backup, mysqldump for database backups, openssl for password generation and AES-256-CBC encryption, systemctl for service control, crontab for scheduling, and ssh for remote script execution - no external libraries or APIs.

Linux system administrators, DevOps engineers, and security or pentesting practitioners who want tested starting templates for backup, monitoring, user management, log analysis, and automation scripts rather than writing each one from scratch.