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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.^[2]

Sar was originally developed for the Unix System V operating system; it is available in AIX, HP-UX, Solaris and other System V based operating systems but it is not available for macOS or FreeBSD. Prior to 2013 there was a bsdsar tool, but it is now deprecated.^[3]

Most Linux distributions provide sar utility through the sysstat package.

sar [-flags] [ -e time ] [ -f filename ] [-i sec ] [ -s time ]

-f

filename Uses filename as the data source for sar. The default is the current daily data file /var/adm/sa/sadd.

-e

time Selects data up to time. The default is 18:00.

-i

sec Selects data at intervals as close as possible to sec seconds.

[user@localhost]$ sar  # Displays current CPU activity.

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

• sar(1): Collect, report, or save system activity information. – Linux User Commands Manual
• sa1(8): Collect and store binary data in the system activity daily data file. – Linux Administration and Privileged Commands Manual
• sa2(8): shell variant of sar, supporting the same flags as sar command which write a daily report in the /var/log/sa directory. – Linux Administration and Privileged Commands Manual
• sadf(1): , similar to sar but can write its data in different formats (CSV, XML, etc.). This is useful to load performance data into a database, or import them in a spreadsheet to make graphs.
• iostat(1): reports basic CPU statistics and input/output statistics for devices, partitions and network filesystems. – Linux User Commands Manual
• mpstat(1): reports individual or combined processor related statistics. – Linux User Commands Manual
• pidstat(1): reports statistics for Linux tasks (processes) : I/O, CPU, memory, etc. – Linux User Commands Manual
• nfsiostat(1): reports input/output statistics for network filesystems (NFS). – Linux User Commands Manual
• cifsiostat(1): reports I/O statistics for CIFS resources. – Linux User Commands Manual

• atopsar
• Nmon
• sag - "system activity graph" command^[5]
• ksar- BSD licensed Java-based application to create graph of all parameters from the data collected by Unix sar utilities.
• CURT, IBM AIX CPU Usage Reporting Tool
• isag, tcl based command to plot sar/sysstat data

• sar(1) – Solaris 11.4 User Commands Reference Manual
• Easy system monitoring with SAR (IBM developerWorks)
• System Activity Reporter (Softpanorama)
• Article on sar at Computerhope