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How to Install and Use System Activity Reporter (SAR) in Linux

How to Install and Use System Activity Reporter (SAR) in Linux
JC Brian Refugia
Technical writer
Linux
12.04.2024
Reading time: 7 min

On Linux-based operating systems, System Activity Reporter (SAR) is an effective command-line utility for tracking system performance. Various system activity indicators, including CPU, RAM, disk I/O, network traffic, and more, are gathered, reported, and analyzed by SAR. This indispensable application helps admins monitor, debug, and optimize Linux servers and workstations proactively by giving rich insights into system behavior. Learn how SAR empowers users to maintain optimal system dependability and efficiency through exact capacity planning, resource allocation, and performance analysis. 

Installing SAR on Linux involves using package managers tailored to what distribution is used. Here's the guide for some well-known Linux distributions: 

Prerequisites

  • System running in Linux Distribution (i.e. Ubuntu, Debian, Centos, Redhat and others).

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  • Root access or user with sudo privileges.

Once all requirements are met, proceed with installation and configuration of SAR.

Installing SAR

  1. Launch the terminal and make sure package list on the system is up to date by issuing the command below:

sudo apt update

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  1. Once the package list is already updated, proceed to install systat package. Run the command below: 

sudo apt install systat

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Systat is a system monitoring tool available for Ubuntu and other Linux variants. It provides several tools and guidelines for monitoring system performance and resource usage. The systat package, which has commands like sar, mpstat, iostat, vmstat, and pidstat, can be used to collect and display system information.

  1. Validate if package was installed successfully by running the command below:

sudo apt list systat

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Collecting System Activity Data with SAR

SAR may not automatically start collecting data after installation. To enable data collection, make modifications to the sysstat configuration file. Before making any changes on the configuration file, make sure to back it up. Run command below:

sudo cp -rp /etc/default/sysstat /etc/default/sysstat.backup

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After backup is completed, proceed to modifying the file by running:          

sudo nano /etc/default/sysstat

Find the line containing ENABLED="false"

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And change it to ENABLED="true":

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Save and exit on the file by Ctrl X and press "Yes" when asked.

In order to initiate data collecting, the sysstat service must run. Use the command below: 

sudo systemctl start sysstat

Confirm if the ssystat service is running. Use the command below:

sudo systemctl status sysstat

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Enable the sysstat service at boot time. This is to make sure the service is running every time server is rebooted or restarted. Use the command 

sudo enable sysstat

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How to Utilize and Operate SAR

A multitude of data is produced by SAR, providing insights into many facets of system performance. A few examples of the output categories are network activity, CPU and memory utilization, disk input/output, and more. Every report includes comprehensive statistics to aid in the diagnosis of performance and system health problems. 

CPU utilization data

Syntax: 

sudo sar -u <interval in seconds> <count>

Note: interval and count can be changed depending on user's requirements.

Example: 

sudo sar -u 2 5

The flag meaning is below:

  • -u - report the CPU utilization
  • 2 - initiate data gathering every 2 seconds
  • 5 - number of times the command will be run

This example displays the output every 2 seconds, 5 times.

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Memory utilization data

Syntax: 

sudo sar -r <interval in seconds> <count>

Note: interval and count can be changed depending on user's requirements.

Example:

sudo sar -r 10 5 

The flag meaning is below:

  • -r - report the Memory utilization
  • 10 - initiate data gathering every 10 seconds
  • 5 - number of times the command will be run

This example displays the output every 10 seconds, 5 times.

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I/O and transfer rate statistics

Syntax: 

sudo sar -b <interval in seconds> <count>

Note: interval and count can be changed depending on user's requirements.

Example:

sudo sar -b 3 7

The flag meaning is below:

  • -b - report the I/O and transfer rate statistics.
  • 3 - initiate data gathering every 3 seconds.
  • 7 - number of times the command will be run.

 This example displays the output every 3 seconds, 7 times.

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Swap utilization data                                         

Syntax: 

sudo sar -S <interval in seconds> <count>

Note: interval and count can be changed depending on user's requirements.

Example:

sudo sar -S 5 5

The flag meaning is below:

  • -S – report the swap utilization statistics.
  • 5 - initiate data gathering every 5 seconds.
  • 5 - number of times the command will be run.

This example displays the output every 5 seconds, 5 times.

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Filesystem statistics                                              

Syntax: 

sudo sar -F <interval in seconds> <count>

Note: interval and count can be changed depending on user's requirements.

Example:

sudo sar -F 5 6

The flag meaning is below:

  • -F - report the filesystem utilization statistics.
  • 5 - initiate data gathering every 5 seconds.
  • 6 - number of times the command will be run.

This example displays the output every 5 seconds, 6 times.

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The SAR report can be saved by appending the output of the gathered data to a file. This can be used for future reference like historical investigation and analysis. Use the >> operator to append the data to a file. 

Example:

sudo sar -r 2 5 >> cpu_stat.txt

In this example, the output of the gathered memory utilization sar report will be appended to the file cpu_stat.txt

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To view if the output is successfully appended to the file cpu_stat.txt, run the command: 

sudo cat cpu_stat.txt

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Customizing SAR Reports 

You can customize the reports by choosing particular metrics, changing the way they are shown, and deciding how often they are collected. The following shows how to customize sar reports: 

  • Determine which metrics should be included in the report based on your monitoring requirements. Some of the common metrics are: 

    • CPU utilization (-u)
    • memory usage (-r)
    • disk I/O (-b)
    • network activity (-n DEV)
    • load average (-q)
  • Customize the display interval. The collection interval can be adjusted by using the -i option followed by the interval in seconds. Example:

sar -i 30

Image5

  • Modify output format to improve readability or prepare it for additional processing. Use the -o option followed by the file name to send the output to a file rather than the terminal in order to reroute it. Example: 

sar -r 2 5 -o output.txt

Image1

  • Integrate several reports into a single output to facilitate analysis by using the -f option followed by the path to the SAR file that you want to combine. Example:

sar -f output.txt >> output_2.txt; sar -f output_2.txt

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  • Produce reports for a specific time frame by using the parameters -s for start time (HH:MM:SS format) and -e for end time (HH:MM:SS). Example:

sar -s 02:00:00 -e 04:00:00

Image4

Conclusion

SAR is essentially a flexible toolkit for system analysis, monitoring, and optimization that helps with effective resource management and provides invaluable insights into system performance. Because of its extensive reporting capabilities and adaptable configuration options, it is a vital tool for preserving the security, stability, and well-being of computing environments.

Linux
12.04.2024
Reading time: 7 min

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Now extract the NATS archive using the installed extractor: unzip nats-server-v2.10.22-linux-amd64.zip Check the file list: ls As you can see, a new folder with the archive contents has appeared: nats-server-v2.10.22-linux-amd64  nats-server-v2.10.22-linux-amd64.zip  resize.log  snap We no longer need the archive, so delete it: rm nats-server-v2.10.22-linux-amd64.zip Installing NATS Server Installation Let's look at the contents of the created folder: ls nats-server-v2.10.22-linux-amd64 Inside it is the main directory with the NATS server: LICENSE  nats-server  README.md This is what we need to copy to the system catalog with binary files: sudo mv nats-server-v2.10.22-linux-amd64/nats-server /usr/local/bin/ After copying, you need to set the appropriate access permissions: sudo chmod +x /usr/local/bin/nats-server The folder with NATS contents, like the archive, can now also be deleted: rm nats-server-v2.10.22-linux-amd64 -R Server Verification Let's verify that the NATS server is installed by requesting its version: nats-server -v A similar output should appear in the console terminal: nats-server: v2.10.22 However, this command doesn't start the server; it only returns its version. 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In this case, when exiting the console, the server will stop working. To prevent this, you need to create a file for the systemd service: sudo nano /etc/systemd/system/nats-server.service Its contents will be: [Unit] Description=NATS message broker server After=syslog.target network.target [Service] Type=simple ExecStart=/usr/local/bin/nats-server -c /etc/nats/nats-server.conf User=nats Group=nats LimitNOFILE=65536 ExecReload=/bin/kill -HUP $MAINPID Restart=on-failure [Install] WantedBy=multi-user.target This file contains several key parameters: Description: Short description of the service ExecStart: NATS server startup command with the configuration file explicitly specified User: Name of the user created for NATS Now we need to set up the service to start up at boot:  systemctl enable nats-server --now The --now flag immediately starts the specified service. The corresponding message will appear in the console: Created symlink /etc/systemd/system/multi-user.target.wants/nats-server.service → /etc/systemd/system/nats-server.service. Now check the status of the running service: systemctl status nats-server If the NATS server service started successfully, the corresponding message will be among the console output: ... Active: active (running) ... Connecting to NATS You can connect to the NATS server through the console terminal and thus perform message broker testing. For example, publish messages or subscribe to subjects. Client Installation To manage the NATS server, you need to install the natscli client. You can download it from the official GitHub repository: wget https://github.com/nats-io/natscli/releases/download/v0.1.5/nats-0.1.5-amd64.deb After this, the downloaded archive can be extracted and installed: dpkg -i nats-0.1.5-amd64.deb The archive itself can be deleted as it's no longer needed: rm nats-0.1.5-amd64.deb Sending Messages Now you can send a message to the message broker: nats pub -s 127.0.0.1 "someSubject" "Some message" In this command, we send the message "Some message" to the subject "someSubject" to the message broker running on IP address 127.0.0.1 and located on the standard NATS port - 4222. After this, information about the sent data will appear in the console terminal: 10:59:51 Published 12 bytes to "someSubject" Reading Messages Currently, no one will see this message since there's no agent subscribed to the specified subject. We can simulate a service subscribed to the subject and reading messages using another SSH session. To do this, you need to open another console terminal, connect to the remote machine, and subscribe to the previously specified subject: nats sub -s 127.0.0.1 "someSubject" A message about successful subscription will appear in the terminal: 11:11:10 Subscribing on someSubject Now repeat sending the message from the first terminal: nats pub -s 127.0.0.1 "someSubject" "Some message" Information about the new message will appear in the second terminal: [#1] Received on "someSubject" Some message Let's send another message from the first terminal: nats pub -s 127.0.0.1 "someSubject" "Some message again" The corresponding notification will appear in the second terminal: [#2] Received on "someSubject" Some message again Note that the console output of received messages has numbering in square brackets. Go Program + NATS Let's create a small program in the Golang programming language using the NATS message broker. Installing Go First, you need to ensure that the Go compiler is installed in the system: go version If the following message appears in the console terminal, then Go is not yet installed: Command 'go' not found, but can be installed with: snap install go # version 1.23.2, or apt install golang-go # version 2:1.18~0ubuntu2 apt install gccgo-go # version 2:1.18~0ubuntu2 See 'snap info go' for additional versions. In this case, you need to download it as an archive from the official website: wget https://go.dev/dl/go1.23.3.linux-amd64.tar.gz -O go.tar.gz And then extracted: sudo tar -xzvf go.tar.gz -C /usr/local As we no longer need the downloaded archive, we can delete it: rm go.tar.gz Next, you need to add the Go compiler to the PATH variable so it can be called from the console terminal: echo export PATH=$HOME/go/bin:/usr/local/go/bin:$PATH >> ~/.profile Then apply the changes: source ~/.profile Verify that Go is installed successfully by requesting its version: go version You will see a similar output: go version go1.23.3 linux/amd64 Creating a Project Let's create a separate folder for the Golang program: mkdir nats_go Then navigate to it: cd nats_go And initialize the Go project: go mod init nats_go Installing the Module After project initialization, you need to install the NATS client from the official GitHub repository. You don't need to download anything manually; it's enough to use the built-in Golang function: go get github.com/nats-io/nats.go/ Writing Code Now you can create a file with the program code: nano nats_go.go Its contents will be: package main import ( "fmt" // module for working with console "os" // module for working with system functions "time" // module for working with time "github.com/nats-io/nats.go" // module for working with NATS server ) func main() { // get NATS server address from environment variable url := os.Getenv("NATS_URL") // if there's no address in environment variable, use default address if url == "" { url = nats.DefaultURL } // connect to NATS server nc, _ := nats.Connect(url) // defer message broker cleanup until main() function completion defer nc.Drain() // send message to subject without subscribers to ensure it disappears nc.Publish("people.philosophers", []byte("Hello, Socrates!")) // subscribe to all sub-subjects in "people" subject sub, _ := nc.SubscribeSync("people.*") // extract message msg, _ := sub.NextMsg(10 * time.Millisecond) // output message status (it's not there because it was sent before subscribing to subjects) fmt.Printf("No message? Answer: %v\n", msg == nil) // send message to "philosophers" sub-subject of "people" subject nc.Publish("people.philosophers", []byte("Hello, Socrates!")) // send message to "physicists" sub-subject of "people" subject nc.Publish("people.physicists", []byte("Hello, Feynman!")) // extract message and output to console msg, _ = sub.NextMsg(10 * time.Millisecond) fmt.Printf("Message: %q in subject %q\n", string(msg.Data), msg.Subject) // extract message and output to console msg, _ = sub.NextMsg(10 * time.Millisecond) fmt.Printf("Message: %q in subject %q\n", string(msg.Data), msg.Subject) // send message to "biologists" sub-subject of "people" subject nc.Publish("people.biologists", []byte("Hello, Darwin!")) // extract message and output to console msg, _ = sub.NextMsg(10 * time.Millisecond) fmt.Printf("Message: %q in subject %q\n", string(msg.Data), msg.Subject) } Now you can run the created program: go run . The program's output will appear in the console terminal: No message? Answer: true Message: "Hello, Socrates!" in subject "people.philosophers" Message: "Hello, Feynman!" in subject "people.physicists" Message: "Hello, Darwin!" in subject "people.biologists" Python Program + NATS As another example, let's consider using the NATS message broker in the Python programming language. First, you need to ensure that the Python interpreter is installed in the system by requesting its version: python --version The corresponding message will appear in the console: Python 3.10.12 Note that this guide uses Python version 3.10.12. Installing PIP To download the NATS client for Python, you first need to install the PIP package manager: apt install python3-pip -y The -y flag helps automatically answer positively to all questions during installation. Installing the Client Now you can install the NATS client for Python: pip install nats-py Creating a Project For the Python program, let's create a separate directory: mkdir nats_python And navigate to it: cd nats_python Writing Code Let's create a file with the program code: nano nats_python.py Its contents will be: import os import asyncio # import NATS client import nats from nats.errors import TimeoutError # get environment variable containing NATS server address servers = os.environ.get("NATS_URL", "nats://localhost:4222").split(",") async def main(): # connect to NATS server nc = await nats.connect(servers=servers) # send message to subject without subscribers to ensure it disappears await nc.publish("people.philosophers", "Hello, Socrates!".encode()) # subscribe to all sub-subjects in "people" subject sub = await nc.subscribe("people.*") try: # extract message msg = await sub.next_msg(timeout=0.1) except TimeoutError: pass # send message to "philosophers" sub-subject of "people" subject await nc.publish("people.philosophers", "Hello, Socrates!".encode()) # send message to "physicists" sub-subject of "people" subject await nc.publish("people.physicists", "Hello, Feynman!".encode()) # extract message and output to console msg = await sub.next_msg(timeout=0.1) print(f"{msg.data.decode('utf-8')} in subject {msg.subject}") # extract message and output to console msg = await sub.next_msg(timeout=0.1) print(f"{msg.data.decode('utf-8')} in subject {msg.subject}") # send message to "biologists" sub-subject of "people" subject await nc.publish("people.biologists", "Hello, Darwin!".encode()) # extract message and output to console msg = await sub.next_msg(timeout=0.1) print(f"{msg.data.decode('utf-8')} in subject {msg.subject}") # unsubscribe from subjects await sub.unsubscribe() # clean up message broker await nc.drain() if __name__ == '__main__': asyncio.run(main()) Now you can run the created script: python nats_python.py The result of its operation will be the following output in the console terminal: Hello, Socrates! in subject people.philosophers Hello, Feynman! in subject people.physicists Hello, Darwin! in subject people.biologists As you can notice, the logic of this Python program doesn't differ from the logic of the Go program. The difference is only in the syntactic constructions of the specific programming language. Conclusion This guide examined the use of the NATS message broker in sequential stages: Downloading and installing NATS from the official GitHub repository Minimal NATS server configuration Managing the NATS server through the console terminal client Using NATS in a Golang program Using NATS in a Python program We downloaded all NATS clients used in this guide (for terminal, Go, and Python) from the official NATS repository on GitHub, which hosts modules and libraries for all programming languages supported by NATS. You can find more detailed information about configuring and using NATS in the official documentation. There are also many examples of using NATS in different programming languages.
24 June 2025 · 13 min to read

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