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The top command is a powerful tool for monitoring system resources and processes on a Linux server. It provides real-time information about CPU, memory, and disk usage, as well as details about running processes. Below is a comprehensive guide on how to use the top command effectively.

Step 1: Open the Terminal

Open a terminal window on your Linux server. You can typically find the terminal application in the applications menu or launch it using a keyboard shortcut such as Ctrl + Alt + T.

or you can make a terminal connection with putty.

Step 2: Run the top Command

Simply type the following command into the terminal and press Enter:

Step 3: Understanding the top Interface

Once you run the top command, you'll see a dynamic display with several sections providing different types of information:

1. Header Information: This section displays general system information, including uptime, total number of users, load averages, and total tasks.

2. Task Area: The task area lists running processes, sorted by various criteria such as CPU usage, memory usage, or process ID (PID). Each process entry displays information such as PID, user, CPU usage, memory usage, command name, and more.

3. System Summary: This section provides summary information about system resource usage, including CPU utilization, memory usage, swap usage, and total processes.

Step 4: Interacting with top

• Navigation: Use arrow keys to navigate through the process list.
• Sorting: Press Shift + P to sort processes by CPU usage, Shift + M to sort by memory usage, and Shift + T to sort by runtime.
• Refreshing: By default, top updates the display every few seconds. You can adjust the refresh interval by pressing s and entering the desired number of seconds.
• Exiting: Press q to quit top and return to the command prompt.

Step 5: Interpretation of Load Averages

Load averages are displayed at the top of the top output. They represent the average number of processes in the system's run queue over the last 1, 5, and 15 minutes, respectively. A load average below the number of CPU cores is generally considered acceptable. High load averages may indicate a system under heavy load or resource contention.

Step 6: Advanced Usage

• Filtering Processes: Press o to open the field selection menu, where you can filter processes based on various criteria.
• Changing Display Options: Press f to open the fields management menu, allowing you to customize which columns are displayed in the process list.
• Batch Mode: Run top -b to run top in batch mode, which outputs information to STDOUT for parsing by other programs or scripts.

Step 7: Monitoring Over Time

For long-term monitoring, you can run top in conjunction with utilities like watch or redirect its output to a file for later analysis:

This command runs top every second (-n 1) and redirects its output to a file called top_output.txt.

Congratulations! You've learned how to use the top command to monitor server load and obtain valuable system information. With this knowledge, you can effectively manage system resources and identify potential performance issues on your Linux server.