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Systems & Data Center · Intermediate

sar

The System Activity Reporter, a sysstat tool that collects and reports historical CPU, memory, disk and network performance data.

Definition

The sysstat service records samples periodically to /var/log/sa (or /var/log/sysstat), and sar reads them back. Options include -u (CPU), -r (memory), -d (disk) and -n DEV (network).

Example

sar -u -f /var/log/sa/sa15 shows CPU usage from the 15th of the month.

Exam tip

Choose sar when you need historical performance data rather than a live snapshot.

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