tail is a command-line utility that allows you to display the last part of files. It is a highly versatile tool, commonly used in system administration and cybersecurity to monitor log files, trace errors, and observe real-time system activities. This utility is available by default on most Unix-based operating systems, such as Linux and macOS.
The basic syntax for the
tail command is:
tail [options] [file_name]
options: Flags that modify the behavior of the command.
file_name: The name of the file you want to display.
Some common options in
-n [lines]: Output the last
[lines]lines, instead of the default last 10 lines.
-f: Follow the file as it grows, displaying new content in real time.
-F: Similar to
-f, but also tries to keep the file open if it’s removed, can’t be accessed or replaced
-q: Quiet mode - never output headers with file names
-s [seconds]: Sleep for approximately
[seconds]between iterations. This is applicable with
- Display the last 10 lines of a file:
- Display the last 50 lines of a file:
tail -n 50 file_name
- Monitor a log file in real time:
tail -f log_file
- Monitor multiple log files in real time:
tail -f log_file1 log_file2 log_file3
Use Cases in Cyber Security
tail is often used by cybersecurity professionals to analyze log files, trace errors, and monitor system activities. Some common use cases include:
- Identifying unauthorized access attempts by monitoring the contents of the
/var/log/auth.logfile in real time:
tail -f /var/log/auth.log
- Analyzing the most recent entries in a web server log file to identify unusual requests or suspicious activities:
tail -n 50 /var/log/apache2/access.log
- Monitoring system log files to quickly identify and respond to security incidents or anomalies:
tail -f /var/log/syslog
tail is a powerful and versatile command-line utility that proves to be an invaluable resource for system administrators and cybersecurity professionals, providing real-time monitoring and analysis of log files and system activities.