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SAR command in Linux to monitor system performance

sar (System Activity Report) It can be used to monitor Linux system’s resources like CPU usage, Memory utilization, I/O devices consumption, Network monitoring, Disk usage, process and thread allocation, battery performance, Plug and play devices, Processor performance, file system and more. Linux system Monitoring and analyzing aids in understanding system resource usage which can help to improve system performance to handle more requests. 

By default, the SAR command displays the result on the output screen, in addition, result can also be stored in the file specified by the -o filename option. 
Any user can collect information about system performance using system activity flags. The SAR command will show only CPU monitoring activity if any flag is not specified by the user. 

Installation of `sar` in Linux

`sar` may not be installed by default. We need to install `sysstat` before using it 

To install `sar` in Ubuntu

sudo apt install sysstat

To install `sar` in RedHat Linux (9)

Sudo dnf install sysstat

Syntax of `sar` command in Linux

sar -[ options ] time_interval number_of_tines_to_display

Examples and Options

To start `sar` Service 

Syntax:

systemctl start sysstat.service

Starting sar service

`–help` option in `sar` command

Syntax:

sar --help

sar –help

We need to enter the root password for authentication.

To verify the `sar` version

Syntax:

sar -V

version of sar

CPU Usage Details

To report CPU details a total of 5 times with the interval of 2 seconds. If the interval command is set to zero, average statistics from the time system started are presented. If the count is not provided and the interval is given, statistics are provided continuously after every interval. 

Syntax:

sar -u 2 5

CPU Usage Details


Memory Usage Details

To report about the amount of memory used, amount of memory free, available cache, available buffers total 3 times with the interval of 1 second. 

Syntax:

sar -r 1 3

Memory Usage

File System Details

To report about file systems mounted on the device total 5 times with the interval of 2 seconds. 

Syntax:

sar -F 2 5

File system

Block Device Details

To report about block devices details total 3 times with the interval of 1 second. 

Syntax:

Blocked Device


Run Queue Length and Load Average

To report run queue length, number of processes and load average 

Syntax:

sar -q 2 5

Run Queue Length and average


CPU Usage for a Specific Core

To report cpu usage for given core

sar -P 1 1 3

CUP usage for a specific core


Network Interface Details

To report about network interface, network speed, IPV4, TCPV4, ICMPV4 network traffic and errors

Syntax:

 sar -n DEV 1 3 | egrep -v lo

Network Interface


Process, Kernel Thread, I-node, and File Table Details

To report details about the process, kernel thread, i-node, and the file tables 

Syntax:

sar -v 1 3


Messages, Semaphores, and Process Details

To report messages, semaphores and processes details for all processors and system-wide. 

sar -mu -P ALL

Swapping Statistics

To report statistics about swapping 

Syntax:

sar -S 1 3

Swapping Statistics


I/O Operation Details

To report details about I/O operations like transaction per second, read per second, write per second.

syntax:

sar -b 1 3

I/O Operations Details


Context Switching, Process Creation, and Swap Details

To report statistics about context switching, number of processes created per second, number of swap per second .

sar -w 1 3


Paging Statistics

To report paging statistics (KBs paged-in/sec, KBs paged-out/sec, pagefault/sec etc.) 

sar -B 2 5

Paging Statics

Conclusion

In this article we discussed The SAR (System Activity Report) command in Linux is a powerful tool for monitoring and analyzing system resources. It provides detailed information on CPU usage, memory utilization, I/O devices, network monitoring, disk usage, and more. SAR helps system administrators and developers understand system performance, identify bottlenecks, and optimize resource allocation for improved efficiency and stability. It is an essential tool for managing and optimizing Linux systems.


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