sar (Unix)

System Activity Report (sar) is a Unix System V-derived system monitor command used to report on various system loads, including CPU activity, memory/paging, interrupts, device load, network and swap space utilization.

Sar uses /proc filesystem for gathering information.

Prior to 2013 there was a bsdsar tool, but it is now deprecated.

[3] Most Linux distributions provide sar utility through the sysstat package.

Additional to sar command, Linux sysstat package in Debian,[4] RedHat Enterprise Linux and SuSE provides additional reporting tools:

Called regularly by cron, sadc does the monitoring and stores its measurements to files in the /var/log/sa/ folder. The sar client can be used to explore this data.