Added information about sar command (#2411)

content/roadmaps/102-devops/content/102-managing-servers/101-live-in-terminal/108-sar.md

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 # Sar
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+`Sar` (**S**ystem **A**activity **R**eport) is a system utility command that is a part of `sysstat` package. It provides details on all aspects of system performance including system load, CPU usage, memory usage, paging, swapping, disk usage, device load, network activity, etc. Sar can display current performance, provide reports that are based on log files stored in your system's `/var/log/sa` or `/var/log/sysstat` folder, or be set up to automatically produce daily reports.
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+Usually, sar's service process (sysstat) runs in the background as a daemon, gathering a set of data every ten minutes. The data for the current day is written in a text file. It is converted to a binary file as each day passes. The files are overwritten each month so they don’t eat up all of your hard drive’s capacity.
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+The basic syntax of the sar command is the following:
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+`sar [OPTIONS]`
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+For example: `sar -r 1 3`
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+To get more information about how to use sar, you can use man command: `man sar`
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+<ResourceGroupTitle>Useful Links</ResourceGroupTitle>
+<BadgeLink colorScheme='blue' badgeText='Man page' href='https://linux.die.net/man/1/sar'>Sar man page</BadgeLink>
+<BadgeLink colorScheme='blue' badgeText='Tutorial' href='https://linuxhint.com/sar_linux_tutorial/'>Sar tutorial for beginners</BadgeLink>