Identifying the Load on Unix Servers

To start the task, you need to connect to the server first using the SSH protocol. Diagnosing server load on Linux involves analyzing various parameters and system resources.

Load Diagnostics Using the top

The top utility in Linux provides an efficient way to monitor and diagnose system load in real time. Let’s consider the main components of its interface, which help quickly identify problems and optimize the use of resources.

root@os ~ # nproc
2

Checking the load with atop

The atop utility in Linux provides detailed information about system load and resources in real time. Let’s consider the main components of its interface, which help quickly identify problems and optimize the use of resources.

The utility allows you to view logs for today, for this type:

atop -r

Useful keys:

• t - go forward in time.
• Shift + t - go back in time.

To view the system load history for previous days in the atop utility, you can use the -r option (replay mode) in combination with specifying a specific date.

atop -r YYYYMMDD

Where YYYYMMDD is the date in YYYYMMDD format, which is the day for which you want to view the load history. For example, 20240405 for April 5, 2024.

atop -r /var/log/atop/atop_20240405

• Use the up and down arrow keys to scroll up and down the screen.
• To move forward and backward in time, use t and Shift+t keys.
• You can use the left and right arrow keys to scroll through the data faster or slower.
• To exit playback mode, press the q key.

Load Diagnostics Using the htop

The htop utility is an interactive monitoring utility for real-time system diagnostics on Linux operating systems. It provides a more convenient and interactive way to diagnose a system than the classic top utility, and can be a useful tool for system administrators and developers.

Diagnosing CPU Load Using the ps Utility

To monitor the load on the processor, you can use the ps utility. The utility provides a lot of information about running processes in the Linux operating system. One way to track CPU usage is to use a combination of options, including sorting by CPU usage. Let’s look at the command:

ps -aux --sort -pcpu

And let’s look at how it can be used to monitor and analyze process activity.

After executing the command, you will get a list of processes sorted by CPU usage in descending order. Each line represents information about a specific process.

When viewing the result, pay attention to the processes that are at the top of the list. If you notice any suspicious processes, you can terminate them by running the command:

kill PID

kill -9 PID

With the kill command you can stop a specific process by specifying its PID. The command killall -9 apache2 will kill all Apache processes on the server. The command killall -u user will kill all user processes.

The -9 option sends a signal that immediately terminates the process, but does not allow it to terminate gracefully. Be careful when using -9, as it may result in data loss or incorrect termination of the process.

Diagnosing the Load on the Nginx web server

If the Nginx web service is installed on the server, using the following command, you can display a list of sites that received the most requests:

tail -n 10000 /var/log/nginx/access.log | awk '{print $6}' | sort -n | uniq -c | sort -nr | head -n10

The following command will list the IPs that received the most requests:

tail -n 10000 /var/log/nginx/access.log | awk '{print $1}' | sort -n | uniq -c | sort -nr | head -n10

With the following command you can block access to the server for IP 1.1.1.1.

iptables -I INPUT -s 1.1.1.1 -j REJECT

To remove a blocking rule, change the -I switch to -D.