NAME
iostat
- report
I/O
statistics
SYNOPSIS
iostat
[-CdDITx]
[-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 use of
-c
presents successive lines averaged over the
wait
period.
The
-I
option causes
iostat
to print raw, unaveraged values.
Only the last disk option specified
-(d,
-D,
or
-x)
is used.
The options are as follows:
- -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.
If no
wait
interval is specified, the default is 1 second.
- -C
-
Show CPU statistics.
This is enabled by default unless the
-d,
-D,
-T,
or
-x
flags are used.
- -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.
- -D
-
Show alternative disk statistics.
Displays kilobytes transferred, number of
transfers, and time spent in transfers.
Use of this flag disables the default display.
- -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
``
/netbsd
''.
- -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.
If no repeat
count
is specified, the default is infinity.
- -x
-
Show extended disk statistics.
Each disk is displayed on a line of its own with all available
statistics.
This option overrides all other display options, and all
disks are displayed unless specific disks
are provided as arguments.
Additionally, separate read and write statistics are displayed.
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 alternative 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
- id
-
% of CPU time in idle mode
FILES
/netbsd
-
Default kernel namelist.
/dev/mem
-
Default memory file.
SEE ALSO
fstat(1),
netstat(1),
nfsstat(1),
ps(1),
systat(1),
vmstat(1),
pstat(8)
The sections starting with ``Interpreting system activity'' in
HISTORY
iostat
appeared in
Version 6 AT&T UNIX
.
The
-x
option was added in
NetBSD1.4.