• telinit <run-level>
    • 0 - halt
    • 1 - single user (to reset the password)
    • 6 - reboot
  • Root prompt is #, user prompt is $
  • Common commands:
    • whoami
    • apropos
    • tar (tape archive: -cvf for create, -xvf for extract)
  • File manipulation:
    • Working with text
    • Soft links, hard links, ., ..
  • Monitoring system performance:
    • top: Use > to switch from highest CPU usage to highest RAM usage; watch for wa (wait time)
    • iotop: Check for disk swap and I/O usage when wait time is high
  • Process management:
    • pkill: Finds and kills processes by pattern (e.g., pkill fox for Firefox)
    • Safer alternative: Use pgrep first to list processes before running pkill
  • Process priority:
    • “Santa Claus has a really big nice level, but he runs slowly” (nice levels affect priority)
  • su stands for substitute user, not superuser