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iostat Command in Linux: Syntax, Options & Practical Examples (Ubuntu)

iostat from the sysstat package reports CPU utilization and per-device disk I/O statistics on Linux. It helps admins spot saturated disks, high iowait, and throughput changes during performance troubleshooting.

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Reviewed byDeepak Prasad

iostat Command in Linux: Syntax, Options & Practical Examples (Ubuntu)
About iostat from the sysstat package reports CPU utilization and per-device disk I/O statistics on Linux. It helps admins spot saturated disks, high iowait, and throughput changes during performance troubleshooting.
Tested on Ubuntu 25.04 (Plucky Puffin); sysstat 12.7.5; kernel 7.0.0-27-generic
Package sysstat (apt/deb) · sysstat (dnf/rpm)
Man page iostat(1)
Privilege none
Distros

Most Linux distributions (sysstat package).

Per-process disk I/O: iotop.

iostat — quick reference

Default reports and intervals

When to use Command
CPU and disk stats since boot (or last boot) iostat
Refresh every N seconds iostat N
N samples at M-second intervals iostat M N
Show version (sysstat package) iostat -V

CPU only

When to use Command
CPU utilization report only iostat -c
CPU stats every 2 seconds iostat -c 2
CPU report with timestamp iostat -c -t

Disk devices

When to use Command
Device throughput only (no CPU header) iostat -d
Extended disk stats (await, %util, …) iostat -x
Extended stats every 2 seconds iostat -x 2
One device only iostat -x sda
Hide devices with zero activity iostat -z
Show device-mapper names instead of dm-N iostat -N

Partitions and units

When to use Command
Include partition rows iostat -p
Partitions on one disk iostat -p sda
All partitions including idle iostat -p ALL
Kilobytes per second iostat -k
Megabytes per second iostat -m
Timestamp on each report iostat -t

Structured output

When to use Command
JSON output for scripts iostat -o JSON
Extended disk stats as JSON iostat -x -o JSON
Shorter column widths iostat -s

iostat — command syntax

Synopsis from sysstat 12.7.5 on Ubuntu 25.04:

text 
iostat [ -c ] [ -d ] [ -h ] [ -k | -m ] [ -N ] [ -s ] [ -t ] [ -V ] [ -x ] [ -y ] [ -z ]

       [ --dec={ 0 | 1 | 2 } ] [ -j { ID | LABEL | PATH | UUID | ... } ]
       [ -o JSON ] [ -p { <device> [,...] | ALL } ] [ <interval> [ <count> ] ]

iostat reads kernel counters; it does not change system state. Historical archives for sar need the sysstat data collector enabled (systemctl enable --now sysstat on Debian/Ubuntu); see the systemctl command for enabling collector units.

iostat — command examples

Essential Default CPU and disk summary

The first screen after boot averages — useful baseline before you add intervals.

Run the command:

bash 
iostat | head -15

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.16    0.04   13.02    1.59    0.00   78.18

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
dm-0            172.93      6243.01       165.76         0.00    1916105      50876          0
sda              93.64      4115.49       135.61         0.00    1273344      41984          0

tps is transfers per second; kB_read/s and kB_wrtn/s are throughput rates.

Essential Live samples every second (interval count)

Pass interval and count to watch a workload for a fixed window.

Run the command:

bash 
iostat 1 2 | head -25

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.17    0.04   13.03    1.59    0.00   78.17

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
dm-0            172.88      6241.18       165.71         0.00    1916105      50876          0
sda              93.64      4115.49       135.61         0.00    1273344      41984          0

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           4.02    0.00    5.03    0.00    0.00   90.95

The second avg-cpu block is the 1-second sample; compare %iowait across intervals during a slow job.

Essential CPU utilization only (-c)

When disk noise is not needed, -c drops the device table.

Run the command:

bash 
iostat -c

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.16    0.04   13.02    1.59    0.00   78.18

High %iowait means CPUs were idle waiting for disk I/O — pair with iostat -x on devices.

Common Extended disk metrics (-x)

-x adds latency and utilization columns — the usual starting point for disk bottlenecks.

Run the command:

bash 
iostat -x sda

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.17    0.04   13.02    1.59    0.00   78.18

Device            r/s     rkB/s   rrqm/s  %rrqm r_await rareq-sz     w/s     wkB/s   wrqm/s  %wrqm w_await wareq-sz     d/s     dkB/s   drqm/s  %drqm d_await dareq-sz     f/s f_await  aqu-sz  %util
sda             78.27   4115.49    29.81  27.58    1.35    52.58    8.44    135.61    11.71  58.11    2.07    16.06    0.00      0.00     0.00   0.00    0.00     0.00    1.10    2.16    0.13   7.53

Watch %util near 100% and await rising — signs the device cannot keep up.

Common Device table without CPU (-d)

Scripts that only care about disk throughput use -d to skip the CPU header.

Run the command:

bash 
iostat -d | head -12

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
dm-0            172.92      6242.60       165.75         0.00    1916105      50876          0
sda              93.64      4115.49       135.61         0.00    1273344      41984          0

Add an interval: iostat -d 2 5 for five samples two seconds apart.

Common Throughput in megabytes (-m)

Large sequential workloads are easier to read in MB/s.

Run the command:

bash 
iostat -m | head -10

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.17    0.04   13.03    1.59    0.00   78.17

Device             tps    MB_read/s    MB_wrtn/s    MB_dscd/s    MB_read    MB_wrtn    MB_dscd
dm-0            172.89         6.10         0.16         0.00       1871         49          0

-k forces kilobytes if your default display differs.

Common Partition-level stats (-p)

See whether one partition on a disk dominates I/O.

Run the command:

bash 
iostat -p | head -12

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.17    0.04   13.03    1.59    0.00   78.17

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
loop0             0.19         3.54         0.00         0.00       1086          0          0
loop5             1.33        19.05         0.00         0.00       5849          0          0

Use iostat -p sda to limit partition rows to one parent disk.

Advanced LVM names with -N

On LVM systems, dm-0 is opaque. -N maps to the volume name.

Run the command:

bash 
iostat -N | head -10

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.15    0.04   12.99    1.58    0.00   78.23

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
ubuntu--vg-ubuntu--lv   172.30      6220.31       165.16         0.00    1916105      50876          0

Combine with -x for extended metrics on named volumes.

Advanced JSON for monitoring scripts (-o JSON)

Export structured data for dashboards or jq parsing.

Run the command:

bash 
iostat -o JSON | head -20

Sample output:

text 
{"sysstat": {
	"hosts": [{
			"nodename": "server1",
			"sysname": "Linux",
			"release": "7.0.0-27-generic",
			"machine": "x86_64",
			"number-of-cpus": 2,
			"date": "07/01/2026",
			"statistics": [
				{
					"avg-cpu":  {"user": 7.15, "nice": 0.04, "system": 12.99, "iowait": 1.58, "steal": 0.00, "idle": 78.23},
					"disk": [
						{"disk_device": "dm-0", "tps": 172.29, "kB_read/s": 6220.11, "kB_wrtn/s": 165.16, "kB_dscd/s": 0.00, "kB_read": 1916105, "kB_wrtn": 50876, "kB_dscd": 0},

Pipe to jq to extract one field in automation.

Advanced Timestamped reports (-t)

Correlate disk spikes with wall-clock time in logs.

Run the command:

bash 
iostat -t | head -10

Sample output:

text 
Linux 7.0.0-27-generic (server1) 	07/01/2026 	_x86_64_	(2 CPU)

07/01/2026 03:35:38 PM
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           7.17    0.04   13.03    1.59    0.00   78.17

Device             tps    kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read    kB_wrtn    kB_dscd
dm-0            172.89      6241.59       165.73         0.00    1916105      50876          0

Use iostat -xt 2 during a deployment window.

iostat — when to use / when not

Use iostat when Use something else when
  • You need per-disk throughput, queue depth, await, or %util
  • CPU %iowait is high and you want to confirm which device is busy
  • You are comparing before/after storage changes with interval samples
  • You want JSON export for monitoring
  • You need the process name doing disk I/O → iotop
  • You need memory and run-queue context → vmstat
  • You need historical trends from yesterday → sar
  • You need network or per-CPU history in one tool → dstat or sar suites

iostat vs iotop

iostat iotop
View Block devices Processes / threads
Key metrics tps, await, %util DISK READ/WRITE per task
Privilege User root
Best question "Is the disk saturated?" "Who is writing?"
Command One line
iostat Device and CPU I/O stats (this page)
pidstat Per-process CPU and I/O

Browse the full index in our Linux commands reference.

iostat — interview corner

What is iostat?

iostat is part of sysstat. It prints CPU utilization and disk I/O statistics per device from kernel counters — either since boot or over sampling intervals.

bash 
iostat -x 1 3

A strong answer is:

"iostat from sysstat shows CPU iowait and per-device throughput and latency. -x adds await and %util for bottleneck analysis."

What are tps and %util?

tps is I/O transfers per second to the device. %util is the percentage of time the device had at least one request in flight — near 100% means the disk is busy most of the sample.

A strong answer is:

"tps counts I/O operations per second; %util is how busy the device was. High %util with high await means a saturated or slow disk."

What does high %iowait mean?

%iowait is CPU time spent idle while waiting for block I/O. It suggests storage or I/O stack delay, not necessarily high CPU user time.

A strong answer is:

"High iowait means CPUs were waiting on disk. I check iostat -x on devices and iotop for the process driving I/O."

How do you read await?

await is average milliseconds for I/O requests (reads and writes combined on the device). Compare across disks and against SLA expectations for your storage type.

A strong answer is:

"await is average I/O completion time in ms. Rising await under load with high %util indicates the device is struggling to keep up."

iostat vs sar?

iostat is for live snapshots on the terminal. sar reads historical sysstat archives when sysstat collection is enabled.

A strong answer is:

"iostat is real-time; sar is historical from /var/log/sysstat. Both come from sysstat."

Troubleshooting

Symptom Likely cause Fix
command not found sysstat not installed sudo apt install sysstat
sar has no history Collector disabled sudo systemctl enable --now sysstat
Too many loop devices Snap/LVM clutter iostat -z or filter device names
dm-0 not meaningful Device mapper Add -N for LVM names
-h prints stats not help sysstat uses -h for human sizes on some versions Use man iostat for options
Rohan Timalsina

is a technical writer and Linux enthusiast who writes practical guides on Linux commands and system administration. He focuses on simplifying complex topics through clear explanations.