Disk and Memory Info

• df → disk partition info
• df -h → human-readable format
• du → size of file/directory
• free → memory info
• cat /proc/cpuinfo → CPU info
• cat /proc/meminfo → memory info

System Logs & Diagnostics

• dmesg → check kernel ring buffer logs
• iostat → check disk I/O stats
• ip route | column -t → check routing table
• ss → view open ports/sockets

Log Directory Structure

• Logs in /var/log/

  • boot → startup records
  • chronyd → NTP info
  • cron → cron jobs
  • maillog → mail daemon
  • secure → login/logout tracking
  • messages → general trace logs
  • httpd → web server errors

Log Monitoring

• tail -f filename → follow log file in real time

System Shutdown & Boot Control

• shutdown → graceful shutdown
• init 0-6 → runlevels (0=off, 3=multi-user, 6=reboot)
• reboot → reboot system
• halt → force shutdown immediately

Hostname Management

• cat /etc/hostname → current hostname
• hostnamectl set-hostname myhostname → change hostname