1.\" $OpenBSD: iostat.8,v 1.23 2007/05/31 19:20:25 jmc Exp $ 2.\" $NetBSD: iostat.8,v 1.10 1996/10/25 18:21:57 scottr Exp $ 3.\" 4.\" Copyright (c) 1985, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" from: @(#)iostat.8 8.1 (Berkeley) 6/6/93 32.\" 33.Dd $Mdocdate: May 31 2007 $ 34.Dt IOSTAT 8 35.Os 36.Sh NAME 37.Nm iostat 38.Nd report I/O statistics 39.Sh SYNOPSIS 40.Nm iostat 41.Op Fl CDdIT 42.Op Fl c Ar count 43.Op Fl M Ar core 44.Op Fl N Ar system 45.Op Fl w Ar wait 46.Op Ar drives 47.Sh DESCRIPTION 48.Nm 49displays kernel I/O statistics on terminal, disk and CPU operations. 50By default, 51.Nm 52displays one line of statistics averaged over the machine's run time. 53The use of 54.Fl c 55presents successive lines averaged over the 56.Ar wait 57period. 58The 59.Fl I 60option causes 61.Nm iostat 62to print raw, unaveraged values. 63.Pp 64The options are as follows: 65.Bl -tag -width Ds 66.It Fl C 67Show CPU statistics. 68This is enabled by default unless the 69.Fl D , 70.Fl d , 71or 72.Fl T 73flags are used. 74.It Fl c Ar count 75Repeat the display 76.Ar count 77times. 78Unless the 79.Fl I 80flag is in effect, the first display is for the time since a reboot and 81each subsequent report is for the time period since the last display. 82If no 83.Ar wait 84interval is specified, the default is 1 second. 85.It Fl D 86Show alternate disk statistics. 87Displays kilobytes transferred, number of 88transfers, and time spent in transfers. 89Use of this flag disables the default display. 90.It Fl d 91Show disk statistics. 92This is the default. 93Displays kilobytes per 94transfer, number of transfers, and megabytes transferred. 95Use of this flag disables display of CPU and tty statistics. 96.It Fl I 97Show the running total values, rather than an average. 98.It Fl M Ar core 99Extract values associated with the name list from the specified 100.Ar core 101instead of the default 102.Pa /dev/mem . 103.It Fl N Ar system 104Extract the name list from the specified 105.Ar system 106instead of the default 107.Dq Pa /bsd . 108.It Fl T 109Show tty statistics. 110This is enabled by default unless the 111.Fl C , 112.Fl D , 113or 114.Fl d 115flags are used. 116.It Fl w Ar wait 117Pause 118.Ar wait 119seconds between each display. 120If no repeat 121.Ar count 122is specified, the default is infinity. 123.El 124.Pp 125.Nm 126displays its information in the following format: 127.Bl -tag -width flag 128.It tty 129.Bl -tag -width indent -compact 130.It tin 131characters read from terminals 132.It tout 133characters written to terminals 134.El 135.It disks 136Disk operations. 137The header of the field is the disk name and unit number. 138If more than four disk drives are configured in the system, 139.Nm 140displays only the first four drives. 141To force 142.Nm 143to display specific drives, their names may be supplied on the command 144line. 145.Pp 146.Bl -tag -width indent -compact 147.It KB/t 148Kilobytes transferred per disk transfer 149.It t/s 150Transfers per second 151.It MB/s 152Megabytes transferred per second 153.Pp 154.El 155The alternate display format, (selected with 156.Fl D ) , 157presents the following values: 158.Pp 159.Bl -tag -width indent -compact 160.It KB 161Kilobytes transferred 162.It xfr 163Disk transfers 164.It time 165Seconds spent in disk activity 166.El 167.It cpu 168.Bl -tag -width indent -compact 169.It \&us 170% of CPU time in user mode 171.It \&ni 172% of CPU time in user mode running niced processes 173.It \&sy 174% of CPU time in system mode 175.It \&in 176% of CPU time processing interrupts 177.It \&id 178% of CPU time in idle mode 179.El 180.El 181.Sh FILES 182.Bl -tag -width /dev/mem -compact 183.It Pa /bsd 184default kernel namelist 185.It Pa /dev/mem 186default memory file 187.El 188.Sh SEE ALSO 189.Xr fstat 1 , 190.Xr netstat 1 , 191.Xr nfsstat 1 , 192.Xr ps 1 , 193.Xr systat 1 , 194.Xr top 1 , 195.Xr pstat 8 , 196.Xr vmstat 8 197.Pp 198The sections starting with 199.Dq Interpreting system activity 200in 201.%T "Installing and Operating 4.3BSD" . 202