[Solved] You want to monitor authentication failures in real-time. Which command combination is best? — Ans: tail -f /var/log/auth.log | grep --line-buffered 'Failed' | Linux CLI

Linux CLI - System Administration

You want to monitor authentication failures in real-time. Which command combination is best?

Agrep 'Failed' /var/log/auth.log

Btail -f /var/log/auth.log | grep --line-buffered 'Failed'

Chead -n 10 /var/log/auth.log

Dcat /var/log/auth.log | grep 'Failed'

Step-by-Step Solution

Solution:

Step 1: Understand real-time monitoring needs
Real-time monitoring requires continuously watching new log lines as they appear.
Step 2: Evaluate command options
tail -f follows new lines live; piping to grep --line-buffered filters lines immediately. Other options only show static content.
Final Answer:
tail -f /var/log/auth.log | grep --line-buffered 'Failed' -> Option B
Quick Check:
tail -f + grep --line-buffered = live filtered logs [OK]

Quick Trick: Use tail -f with grep --line-buffered for live filtered logs [OK]

Common Mistakes:

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