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IOSTAT(8) FreeBSD System Manager's Manual IOSTAT(8) NAME iostat - report I/O statistics SYNOPSIS iostat [-CDdIT] [-c count] [-M core] [-N system] [-w wait] [drives] DESCRIPTION iostat displays kernel I/O statistics on terminal, disk and CPU operations. By default, iostat displays one line of statistics averaged over the machine's run time. The -I option causes iostat to print raw, unaveraged values. The options are as follows: -C Show CPU statistics. This is enabled by default unless the -D, -d, or -T flags are used. -c count Repeat the display count times. Unless the -I flag is in effect, the first display is for the time since a reboot and each subsequent report is for the time period since the last display. Unless overridden by the -w option, the wait interval between lines is 1 second. -D Show alternate disk statistics. Displays kilobytes transferred, number of transfers, and time spent in transfers. Use of this flag disables the default display. -d Show disk statistics. This is the default. Displays kilobytes per transfer, number of transfers, and megabytes transferred. Use of this flag disables display of CPU and tty statistics. -I Show the running total values, rather than an average. -M core Extract values associated with the name list from the specified core instead of the default /dev/mem. -N system Extract the name list from the specified system instead of the default "/bsd". -T Show tty statistics. This is enabled by default unless the -C, -D, or -d flags are used. -w wait Pause wait seconds between each display. Unless a count is specified via the -c option, iostat will display output until it is interrupted. iostat displays its information in the following format: tty tin characters read from terminals tout characters written to terminals disks Disk operations. The header of the field is the disk name and unit number. If more than four disk drives are configured in the system, iostat displays only the first four drives. To force iostat to display specific drives, their names may be supplied on the command line. KB/t Kilobytes transferred per disk transfer t/s Transfers per second MB/s Megabytes transferred per second The alternate display format, selected with -D, presents the following values: KB Kilobytes transferred xfr Disk transfers time Seconds spent in disk activity cpu us % of CPU time in user mode ni % of CPU time in user mode running niced processes sy % of CPU time in system mode sp % of CPU time spent spinning in % of CPU time processing interrupts id % of CPU time in idle mode FILES /bsd default kernel namelist /dev/mem default memory file SEE ALSO fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), top(1), pstat(8), vmstat(8) The sections starting with "Interpreting system activity" in Installing and Operating 4.3BSD. FreeBSD 14.1-RELEASE-p8 September 17, 2022 FreeBSD 14.1-RELEASE-p8