Understanding CPU processor usage is important for overall system-performance measurement. From Linux enthusiasts to system admins, knowing how to monitor CPU utilization in Linux from the command line is crucial.
This guide will walk you through several options to check Linux CPU usage.
- A Linux-based computer (e.g., Ubuntu and CentOS)
- Access to a user account with sudo privileges
- A command prompt (Ctrl-Alt-T in Ubuntu, Menu > Applications > Utilities > Terminal in CentOS)
- (optional) A package installer, like apt or yum, usually included by default
Note: Use one of 5 available commands in Linux to check memory usage.
How To Check CPU Usage from Linux Command Line
top Command to View Linux CPU Load
Open a terminal window and enter the following:
The system should respond by displaying a list of all the processes that are currently running. It will also give a readout of users, tasks, CPU load, and memory usage.
This list can frequently change, as background tasks start and complete. One helpful switch is to launch
top with the
This hides all the idle processes, making it easier to sort through the list.
To quit the
top function, press the letter q on your keyboard.
Some other useful commands while
top is running include:
M– sort task list by memory usage
P– sort task list by processor usage
N– sort task list by process ID
T– sort task list by run time
To get assistance with
top, you can press the letter h while it’s running. Or, you can enter the following at a command line:
This will display the manual page for the
mpstat Command to Display CPU Activity
Mpstat is part of a software bundle called sysstat. Most RHEL-based distributions include this software package.
For Debian and Ubuntu systems, you’ll need to install the sysstat package.
In a terminal window, enter the following:
sudo apt-get install sysstat
Allow the process to complete.
If you’re running an older (4.x or older) version of CentOS or Red Hat derivative, you can use up2date to install sysstat:
sudo up2date install sysstat
For newer (5.x and later) installations of CentOS or Red Hat, sysstat can be installed using the following command:
sudo yum install sysstat
Once the process finishes, you can use the
mpstat command in the terminal as follows:
The system will display usage for each processor (or processor core).
The first line is a set of column labels. The second line is the value for each column:
- %usr – % CPU usage at the user level
- %nice – % CPU usage for user processes labeled “nice”
- %sys – % CPU usage at the system (Linux kernel) level
- %iowait – % CPU usage idling waiting on a disk read/write
- %irq – % CPU usage handling hardware interrupts
- %soft – % CPU usage handing software interrupts
- %steal – % CPU usage being forced to wait for a hypervisor handling other virtual processors
- %guest – % CPU usage spent running a virtual processor
- %idle – % CPU usage on idle time (no processes, and not waiting on a disk read/write)
You can add switches to the
–P switch allows you to specify a single processor to report:
mpstat –P 0
This would show you a report for the first processor (CPU 0).
mpstat –P ALL
This command would show you the total, like the basic
mpstat command. It will also list processes by individual CPU.
mpstat command only takes a snapshot of CPU usage.
To take a series of snapshots, use a number to indicate an interval and a second number to indicate the number of reports:
mpstat 5 7
This example would generate 7 snapshots, each 5 seconds apart.
sar Command to Show CPU Utilization
The sar tool is a utility for managing system resources. It’s not limited strictly to CPU usage, but you can use the
-u option to track CPU performance.
Use the following command to direct sar to monitor CPU usage at set intervals:
sar –u 5
–u option tells it to display CPU usage. The 5 indicates that it should display every 5 seconds. This will run indefinitely. To cancel, press Ctrl-C.
iostat Command for Average Usage
In a terminal, enter the following:
The system will display average CPU usage since the last boot. It will also display input/output load (disk read/write activity).
More information on iostat can be found on the Linux Manual pages.
Other Options to Monitor CPU Performance
Nmon Monitoring Tool
Nmon is a monitoring tool developed by Nigel Griffiths of IBM. To install Nmon on Ubuntu, enter the following:
sudo apt-get install nmon
To install to CentOS, enter the following:
sudo yum epel-release
sudo yum install nmon
The command to launch nmon is:
This will launch the utility, and display all the options. To view CPU usage, press the letter c. To switch back, press c again. For a list of commands, press h. To quit, press q.
Graphical Utility Option
Many server systems don’t waste processor cycles on a graphical user interface (GUI).
However, you may have a lightweight GUI, or you may be using a client Linux system. Some versions, like Ubuntu, have a built-in graphical monitoring tool.
To launch Ubuntu’s system monitor, enter the following in a terminal window:
This starts a task-manager-like application where you can monitor tasks and CPU usage.
Typically, GUI’s have a “task manager” or “system monitor” application. This can be used to monitor CPU usage in real-time.
There are many different methods to check CPU usage in Linux.
This guide outlines the primary methods using built-in Linux tools or third-party applications. These commands will help you track processor usage and performance of your system, giving you greater control.