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Intermediate LinuxLesson 10 of 27 1 min read

Processes and the System

ps, top, kill, and how to find what is running.

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A process is a running program. Linux gives every process a numeric ID called a PID.

Inspecting processes

bash
ps aux                 # snapshot of all processes
top                    # live, updating view (q to quit)
pgrep -a node          # find processes by name

Killing processes

bash
kill 1234              # polite shutdown (SIGTERM)
kill -9 1234           # force kill (SIGKILL) - last resort
pkill -f "python app"  # kill by pattern

System info

bash
uname -a               # kernel info
uptime                 # how long the system has been up
free -h                # memory usage
df -h                  # disk space

Foreground vs background

  • Run normally: python app.py (foreground)
  • Run in background: python app.py &
  • Bring back to foreground: fg

These tools are your first stop when something is wrong on a server.

Challenge

Show the top of the ps aux output filtered to lines containing the word root.

Want to experiment first? Try things in the practice terminal (opens in a new tab), then enter the command that solves the task here.

Quiz

Lock in the concepts. Score at least 80% to mark the lesson complete.

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