iostat: Report CPU and I/O Statistics

IOSTAT(1) Linux User’s Manual IOSTAT(1) NAME iostat - Report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions. SYNOPSIS iostat [ -c ] [ -d ] [ -h ] [ -k | -m ] [ -N ] [ -s ] [ -t ] [ -V ] [ -x ] [ -y ] [ -z ] [ --compact ] [ --dec={ 0 | 1 | 2 } ] [ { -f | +f } directory ] [ -j { ID | LABEL | PATH | UUID | ... } ] [ -o JSON ] [ [ -H ] -g group_name ] [ --human ] [ --pretty ] [ -p [ device[,...] | ALL ] ] [ device [...] | ALL ] [ interval [ count ] ] DESCRIPTION The iostat command is used for monitoring system input/output device loading by observing the time the devices are active in relation to their average transfer rates. The iostat command generates reports that can be used to change system configuration to better balance the input/output load between physical disks. The first report generated by the iostat command provides statistics concerning the time since the system was booted, unless the -y option is used (in this case, this first report is omitted). Each subsequent report covers the time since the previous report. All statistics are reported each time the iostat command is run. The report consists of a CPU header row followed by a row of CPU statistics. On multiprocessor systems, CPU statistics are calculated system-wide as averages among all processors. A device header row is displayed followed by a line of statistics for each device that is configured. The interval parameter specifies the amount of time in seconds between each report. The count parameter can be specified in conjunction with the interval parameter. If the count parameter is specified, the value of count determines the number of reports generated at interval seconds apart. If the interval parameter is specified without the count parameter, the iostat command generates reports continuously. REPORTS The iostat command generates two types of reports, the CPU Utilization report and the Device Utilization report. CPU Utilization Report The first report generated by the iostat command is the CPU Utilization Report. For multiprocessor systems, the CPU values are global averages among all processors. The report has the following format: %user Show the percentage of CPU utilization that occurred while executing at the user level (application). %nice Show the percentage of CPU utilization that occurred while executing at the user level with nice priority. %system Show the percentage of CPU utilization that occurred while executing at the system level (kernel). %iowait Show the percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request. %steal Show the percentage of time spent in involuntary wait by the virtual CPU or CPUs while the hypervisor was servicing another virtual processor. %idle Show the percentage of time that the CPU or CPUs were idle and the system did not have an outstanding disk I/O request. Device Utilization Report The second report generated by the iostat command is the Device Utilization Report. The device report provides statistics on a per physical device or partition basis. Block devices and partitions for which statistics are to be displayed may be entered on the command line. If no device nor partition is entered, then statistics are displayed for every device used by the system, and providing that the kernel main‐ tains statistics for it. If the ALL keyword is given on the command line, then statistics are displayed for every device defined by the system,

The `iostat` command is used to monitor system I/O device loading and CPU utilization. It generates reports showing the time devices are active and their average transfer rates. The command can be used to identify I/O bottlenecks and optimize system configuration. It outputs CPU utilization statistics (user, nice, system, iowait, steal, idle) and device utilization statistics on a per-device or per-partition basis. Reports can be generated at specified intervals and for a set number of times. By default, it reports statistics for all devices used by the system.