Prerequisites

In order to complete this tutorial, you will need to have an Ubuntu 18.04 server with a non-root sudo-enabled user account and a basic firewall. This can be configured using our initial server setup guide for Ubuntu 18.04.

Installing sar/sysstat

First, let’s start by updating your local repositories:

sudo apt update

After that as the sar command is part of the sysstat package in order to install it, you need to run the following command:

sudo apt install sysstat

After that you can check the sar version by running the following:

sar -V

Configuring sar/sysstat

After the installation, make sure to start and enable the sysstat service:

sudo systemctl start sysstat
sudo systemctl enable sysstat

This will add the required cron jobs so that the system data is collected accordingly.

The cron jobs will be added at:

cat /etc/cron.d/sysstat

And the file will look like this:

# The first element of the path is a directory where the debian-sa1
# script is located
PATH=/usr/lib/sysstat:/usr/sbin:/usr/sbin:/usr/bin:/sbin:/bin

# Activity reports every 10 minutes everyday
5-55/10 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1

# Additional run at 23:59 to rotate the statistics file
59 23 * * * root command -v debian-sa1 > /dev/null && debian-sa1 60 2

Using of sar

In order to

The sar command has a lot of arguments and options, but here is a list of some of the most popular ones which you might need:

Let’s start by checking the CPU usage on your server:

sar -u

This will show you the CPU usage for the current day.

If you wanted to check the current usage in real-time, you could specify 2 more arguments:

sar -u 2 30

The first argument which is 2 means that the sar command should run every 2 seconds and the second 30 means that the command should be executed 30 times.

That way you will see on your screen your CPU usage every 2 seconds for 30 times:

sar 1 30
Linux 4.15.0-101-generic (docker)       11/03/20        _x86_64_        (2 CPU)

14:21:16        CPU     %user     %nice   %system   %iowait    %steal     %idle
14:21:17        all      1.00      0.00      0.50      0.00      0.00     98.51
14:21:18        all      0.00      0.00      0.00      0.00      0.00    100.00
14:21:19        all      0.00      0.00      0.00      0.00      0.00    100.00
14:21:20        all      0.00      0.00      0.50      0.00      0.00     99.50
14:21:21        all      1.00      0.00      0.50      0.00      0.00     98.51
14:21:22        all      2.48      0.00      0.50      0.00      0.00     97.03
14:21:23        all      1.00      0.00      0.00      0.00      0.00     99.00
14:21:24        all      0.50      0.00      0.50      0.00      0.00     99.00

If you wanted to check your Memory usage instead, you could use the -r argument rather than -u.

sar -r 2 30

Some other useful arguments are -b which shows the Disk I/O usage and the -n which shows the network usage.

For more information make sure to check the man pages:

https://manpages.debian.org/testing/sysstat/sar.sysstat.1.en.html

Conclusion

The sysstat package also provides you with other useful tools like:

• iostat - reports CPU statistics and input/output statistics for block devices and partitions.

• mpstat - reports individual or combined processor related statistics.

• pidstat - reports statistics for Linux tasks (processes) : I/O, CPU, memory, etc.

• tapestat - reports statistics for tape drives connected to the system.

• cifsiostat - reports CIFS statistics.

• Sysstat - also contains tools you can schedule via cron or systemd to collect and historize performance and activity data:

• sar - collects, reports and saves system activity information (see below a list of metrics collected by sar).

• sadc - is the system activity data collector, used as a backend for sar.

• sa1 - collects and stores binary data in the system activity daily data file. It is a front end to sadc designed to be run from cron or systemd.

• sa2 - writes a summarized daily activity report. It is a front end to sar designed to be run from cron or systemd.

• sadf - displays data collected by sar in multiple formats (CSV, XML, JSON, etc.) and can be used for data exchange with other programs. This command can also be used to * draw - graphs for the various activities collected by sar using SVG (Scalable Vector Graphics) format.

If you like the tool make sure to star it on GitHub and contribute:

https://github.com/sysstat/sysstat

Hope that this helps!