{
    "mode": "man",
    "parameter": "IOSTAT",
    "section": "1",
    "url": "https://www.chedong.com/phpMan.php/man/IOSTAT/1/json",
    "generated": "2026-11-09T18:52:51Z",
    "synopsis": "",
    "sections": {
        "NAME": {
            "content": "iostat  - Report Central Processing Unit (CPU) statistics and input/output statistics for de‐\nvices and partitions.\n\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "",
            "subsections": [
                {
                    "name": "iostat [ -c ] [ -d ] [ -h ] [ -k | -m ] [ -N ] [ -s ] [ -t ] [ -V ] [ -x ] [ -y ] [  -z  ]  [",
                    "content": "--compact ] [ --dec={ 0 | 1 | 2 } ] [ { -f | +f } directory ] [ -j { ID | LABEL | PATH | UUID\n| ... } ] [ -o JSON ] [ [ -H ] -g groupname ] [ --human ] [ --pretty ] [ -p [ device[,...] |\nALL ] ] [ device [...] | ALL ] [ interval [ count ] ]\n\n"
                }
            ]
        },
        "DESCRIPTION": {
            "content": "The iostat command is used for monitoring system input/output device loading by observing the\ntime  the  devices are active in relation to their average transfer rates. The iostat command\ngenerates reports that can be used to change system configuration to better balance  the  in‐\nput/output load between physical disks.\n\nThe  first  report  generated  by  the iostat command provides statistics concerning the time\nsince the system was booted, unless the -y option is used (in this case, this first report is\nomitted).  Each subsequent report covers the time since the previous report.  All  statistics\nare  reported  each  time  the iostat command is run. The report consists of a CPU header row\nfollowed by a row of CPU statistics. On multiprocessor systems, CPU statistics are calculated\nsystem-wide as averages among all processors. A device header row is displayed followed by  a\nline of statistics for each device that is configured.\n\nThe interval parameter specifies the amount of time in seconds between each report. The count\nparameter can be specified in conjunction with the interval parameter. If the count parameter\nis  specified, the value of count determines the number of reports generated at interval sec‐\nonds apart. If the interval parameter is specified without the count  parameter,  the  iostat\ncommand generates reports continuously.\n\n",
            "subsections": []
        },
        "REPORTS": {
            "content": "The  iostat command generates two types of reports, the CPU Utilization report and the Device\nUtilization report.\n\n\nCPU Utilization Report\nThe first report generated by the iostat command is the CPU  Utilization  Report.  For\nmultiprocessor  systems, the CPU values are global averages among all processors.  The\nreport has the following format:\n\n%user  Show the percentage of CPU utilization that occurred  while  executing  at  the\nuser level (application).\n\n%nice  Show  the  percentage  of  CPU utilization that occurred while executing at the\nuser level with nice priority.\n\n%system\nShow the percentage of CPU utilization that occurred  while  executing  at  the\nsystem level (kernel).\n\n%iowait\nShow  the  percentage  of  time that the CPU or CPUs were idle during which the\nsystem had an outstanding disk I/O request.\n\n%steal Show the percentage of time spent in involuntary wait by  the  virtual  CPU  or\nCPUs while the hypervisor was servicing another virtual processor.\n\n%idle  Show  the  percentage of time that the CPU or CPUs were idle and the system did\nnot have an outstanding disk I/O request.\n\nDevice Utilization Report\nThe second report generated by the iostat command is the  Device  Utilization  Report.\nThe  device  report  provides  statistics on a per physical device or partition basis.\nBlock devices and partitions for which statistics are to be displayed may  be  entered\non  the command line.  If no device nor partition is entered, then statistics are dis‐\nplayed for every device used by the system, and providing that  the  kernel  maintains\nstatistics  for  it.  If the ALL keyword is given on the command line, then statistics\nare displayed for every device defined by the system, including those that have  never\nbeen  used.   Transfer rates are shown in 1K blocks by default, unless the environment\nvariable POSIXLYCORRECT is set, in which case 512-byte blocks are used.   The  report\nmay  show  the  following  fields, depending on the flags used (e.g.  -x, -s and -k or\n-m):\n\nDevice:\nThis column gives the device (or partition) name as listed in the  /dev  direc‐\ntory.\n\ntps    Indicate  the  number of transfers per second that were issued to the device. A\ntransfer is an I/O request to the device. Multiple logical requests can be com‐\nbined into a single I/O request to the device. A transfer is  of  indeterminate\nsize.\n\nBlkread/s (kBread/s, MBread/s)\nIndicate  the  amount  of  data  read  from the device expressed in a number of\nblocks (kilobytes, megabytes) per second. Blocks are equivalent to sectors  and\ntherefore have a size of 512 bytes.\n\nBlkwrtn/s (kBwrtn/s, MBwrtn/s)\nIndicate  the  amount  of  data  written to the device expressed in a number of\nblocks (kilobytes, megabytes) per second.\n\nBlkdscd/s (kBdscd/s, MBdscd/s)\nIndicate the amount of data discarded for the device expressed in a  number  of\nblocks (kilobytes, megabytes) per second.\n\nBlkw+d/s (kBw+d/s, MBw+d/s)\nIndicate the amount of data written to or discarded for the device expressed in\na number of blocks (kilobytes, megabytes) per second.\n\nBlkread (kBread, MBread)\nThe total number of blocks (kilobytes, megabytes) read.\n\nBlkwrtn (kBwrtn, MBwrtn)\nThe total number of blocks (kilobytes, megabytes) written.\n\nBlkdscd (kBdscd, MBdscd)\nThe total number of blocks (kilobytes, megabytes) discarded.\n\nBlkw+d (kBw+d, MBw+d)\nThe total number of blocks (kilobytes, megabytes) written or discarded.\n\nr/s    The number (after merges) of read requests completed per second for the device.\n\nw/s    The  number  (after  merges) of write requests completed per second for the de‐\nvice.\n\nd/s    The number (after merges) of discard requests completed per second for the  de‐\nvice.\n\nf/s    The  number  (after  merges) of flush requests completed per second for the de‐\nvice.  This counts flush requests executed by disks.  Flush  requests  are  not\ntracked  for  partitions.  Before being merged, flush operations are counted as\nwrites.\n\nsec/s (kB/s, MB/s)\nThe number of sectors (kilobytes, megabytes) read from, written to or discarded\nfor the device per second.\n\nrsec/s (rkB/s, rMB/s)\nThe number of sectors (kilobytes, megabytes) read from the device per second.\n\nwsec/s (wkB/s, wMB/s)\nThe number of sectors (kilobytes, megabytes) written to the device per second.\n\ndsec/s (dkB/s, dMB/s)\nThe number of sectors (kilobytes, megabytes) discarded for the device per  sec‐\nond.\n\nrqm/s  The number of I/O requests merged per second that were queued to the device.\n\nrrqm/s The number of read requests merged per second that were queued to the device.\n\nwrqm/s The number of write requests merged per second that were queued to the device.\n\ndrqm/s The  number  of  discard requests merged per second that were queued to the de‐\nvice.\n\n%rrqm  The percentage of read requests merged together before being sent  to  the  de‐\nvice.\n\n%wrqm  The  percentage  of write requests merged together before being sent to the de‐\nvice.\n\n%drqm  The percentage of discard requests merged together before being sent to the de‐\nvice.\n\nareq-sz\nThe average size (in kilobytes) of the I/O requests that were issued to the de‐\nvice.\nNote: In previous versions, this field was known as avgrq-sz and was  expressed\nin sectors.\n\nrareq-sz\nThe  average  size  (in kilobytes) of the read requests that were issued to the\ndevice.\n\nwareq-sz\nThe average size (in kilobytes) of the write requests that were issued  to  the\ndevice.\n\ndareq-sz\nThe average size (in kilobytes) of the discard requests that were issued to the\ndevice.\n\nawait  The  average time (in milliseconds) for I/O requests issued to the device to be\nserved. This includes the time spent by the requests  in  queue  and  the  time\nspent servicing them.\n\nrawait\nThe average time (in milliseconds) for read requests issued to the device to be\nserved.  This  includes  the  time  spent by the requests in queue and the time\nspent servicing them.\n\nwawait\nThe average time (in milliseconds) for write requests issued to the  device  to\nbe  served.  This includes the time spent by the requests in queue and the time\nspent servicing them.\n\ndawait\nThe average time (in milliseconds) for discard requests issued to the device to\nbe served. This includes the time spent by the requests in queue and  the  time\nspent servicing them.\n\nfawait\nThe  average  time (in milliseconds) for flush requests issued to the device to\nbe served.  The block layer combines flush requests and executes at most one at\na time.  Thus flush operations could be twice as long: Wait for  current  flush\nrequest, then execute it, then wait for the next one.\n\naqu-sz The average queue length of the requests that were issued to the device.\nNote: In previous versions, this field was known as avgqu-sz.\n\n%util  Percentage  of elapsed time during which I/O requests were issued to the device\n(bandwidth utilization for the device).  Device  saturation  occurs  when  this\nvalue  is close to 100% for devices serving requests serially.  But for devices\nserving requests in parallel, such as RAID arrays and modern SSDs, this  number\ndoes not reflect their performance limits.\n\n",
            "subsections": []
        },
        "OPTIONS": {
            "content": "",
            "subsections": [
                {
                    "name": "-c",
                    "content": "",
                    "flag": "-c"
                },
                {
                    "name": "--compact",
                    "content": "Don't break the Device Utilization Report into sub-reports so that all the metrics get\ndisplayed on a single line.\n",
                    "long": "--compact"
                },
                {
                    "name": "-d",
                    "content": "",
                    "flag": "-d"
                },
                {
                    "name": "--dec={ 0 | 1 | 2 }",
                    "content": "Specify the number of decimal places to use (0 to 2, default value is 2).\n",
                    "long": "--dec",
                    "arg": "{"
                },
                {
                    "name": "-f",
                    "content": "+f directory\nSpecify  an  alternative  directory  for  iostat to read devices statistics. Option -f\ntells iostat to use only the files located in the alternative directory,  whereas  op‐\ntion  +f  tells  it to use both the standard kernel files and the files located in the\nalternative directory to read device statistics.\n\ndirectory is a directory containing files with statistics for devices managed in user‐\nspace.  It may contain:\n\n- a \"diskstats\" file whose format is compliant with that located in \"/proc\",\n- statistics for individual devices contained in files whose format is compliant  with\nthat of files located in \"/sys\".\n\nIn particular, the following files located in directory may be used by iostat:\n\ndirectory/block/device/stat\ndirectory/block/device/partition/stat\n\npartition files must have an entry in directory/dev/block/ directory, e.g.:\n\ndirectory/dev/block/major:minor --> ../../block/device/partition\n",
                    "flag": "-f"
                },
                {
                    "name": "-g",
                    "content": "Display  statistics for a group of devices.  The iostat command reports statistics for\neach individual device in the list then a line of global statistics for the group dis‐\nplayed as groupname and made up of all the devices in the list. The ALL keyword means\nthat all the block devices defined by the system shall be included in the group.\n",
                    "flag": "-g"
                },
                {
                    "name": "-H      -g",
                    "content": "the group are to be displayed, and not statistics for individual devices in the group.\n",
                    "flag": "-g"
                },
                {
                    "name": "-h      --human --pretty",
                    "content": "",
                    "flag": "-h",
                    "long": "--pretty"
                },
                {
                    "name": "--human",
                    "content": "Print sizes in human readable format (e.g. 1.0k, 1.2M, etc.)  The units displayed with\nthis option supersede any other default units (e.g.  kilobytes, sectors...) associated\nwith the metrics.\n",
                    "long": "--human"
                },
                {
                    "name": "-j { ID | LABEL | PATH | UUID | ... } [",
                    "content": "Display persistent device names. Keywords ID, LABEL, etc. specify the type of the per‐\nsistent name. These keywords are not limited, only prerequisite is that directory with\nrequired  persistent  names is present in /dev/disk.  Optionally, multiple devices can\nbe specified in the chosen persistent name type.  Because persistent device names  are\nusually long, option --pretty is implicitly set with this option.\n",
                    "flag": "-j",
                    "arg": "UUID"
                },
                {
                    "name": "-k",
                    "content": "",
                    "flag": "-k"
                },
                {
                    "name": "-m",
                    "content": "",
                    "flag": "-m"
                },
                {
                    "name": "-N",
                    "content": "viewing LVM2 statistics.\n",
                    "flag": "-N"
                },
                {
                    "name": "-o JSON",
                    "content": "Display the statistics in JSON (JavaScript Object Notation) format.  JSON output field\norder is undefined, and new fields may be added in the future.\n",
                    "flag": "-o",
                    "arg": "JSON"
                },
                {
                    "name": "-p [ {",
                    "content": "Display statistics for block devices and all their partitions that  are  used  by  the\nsystem.   If  a device name is entered on the command line, then statistics for it and\nall its partitions are displayed. Last, the ALL keyword indicates that statistics have\nto be displayed for all the block devices and partitions defined by  the  system,  in‐\ncluding  those  that have never been used. If option -j is defined before this option,\ndevices entered on the command line can be specified with the chosen  persistent  name\ntype.\n",
                    "flag": "-p"
                },
                {
                    "name": "--pretty",
                    "content": "Make the Device Utilization Report easier to read by a human.  The device name will be\nprinted on the right side. The report may also be broken into sub-reports if there are\nmany metrics to display (use --compact option to prevent this).\n",
                    "long": "--pretty"
                },
                {
                    "name": "-s",
                    "content": "screens.\n",
                    "flag": "-s"
                },
                {
                    "name": "-t",
                    "content": "of the STIMEFORMAT environment variable (see below).\n",
                    "flag": "-t"
                },
                {
                    "name": "-V",
                    "content": "",
                    "flag": "-V"
                },
                {
                    "name": "-x",
                    "content": "",
                    "flag": "-x"
                },
                {
                    "name": "-y",
                    "content": "given interval.\n",
                    "flag": "-y"
                },
                {
                    "name": "-z",
                    "content": "sample period.\n\n",
                    "flag": "-z"
                }
            ]
        },
        "ENVIRONMENT": {
            "content": "The iostat command takes into account the following environment variables:\n\nPOSIXLYCORRECT\nWhen  this variable is set, transfer rates are shown in 512-byte blocks instead of the\ndefault 1K blocks.\n\nSCOLORS\nBy default statistics are displayed in color when the output is connected to a  termi‐\nnal.   Use this variable to change the settings. Possible values for this variable are\nnever, always or auto (the latter is equivalent to the default settings).\nPlease note that the color (being red, yellow, or some other color) used to display  a\nvalue  is not indicative of any kind of issue simply because of the color. It only in‐\ndicates different ranges of values.\n\nSCOLORSSGR\nSpecify the colors and other attributes used to display statistics  on  the  terminal.\nIts   value   is   a   colon-separated   list   of   capabilities   that  defaults  to\nH=31;1:I=32;22:M=35;1:N=34;1:Z=34;22.  Supported capabilities are:\n\nH=     SGR (Select Graphic Rendition) substring for percentage values greater than  or\nequal to 75%.\n\nI=     SGR substring for device names.\n\nM=     SGR substring for percentage values in the range from 50% to 75%.\n\nN=     SGR substring for non-zero statistics values.\n\nZ=     SGR substring for zero values.\n\nSTIMEFORMAT\nIf  this  variable exists and its value is ISO then the current locale will be ignored\nwhen printing the date in the report header. The iostat command will use the ISO  8601\nformat (YYYY-MM-DD) instead.  The timestamp displayed with option -t will also be com‐\npliant with ISO 8601 format.\n\n",
            "subsections": []
        },
        "EXAMPLES": {
            "content": "iostat Display a single history since boot report for all CPU and Devices.\n",
            "subsections": [
                {
                    "name": "iostat -d 2",
                    "content": "Display a continuous device report at two second intervals.\n"
                },
                {
                    "name": "iostat -d 2 6",
                    "content": "Display six reports at two second intervals for all devices.\n"
                },
                {
                    "name": "iostat -x sda sdb 2 6",
                    "content": "Display six reports of extended statistics at two second intervals for devices sda and\nsdb.\n"
                },
                {
                    "name": "iostat -p sda 2 6",
                    "content": "Display  six  reports  at  two  second intervals for device sda and all its partitions\n(sda1, etc.)\n\n"
                }
            ]
        },
        "BUGS": {
            "content": "/proc filesystem must be mounted for iostat to work.\n\nKernels older than 2.6.x are no longer supported.\n\nAlthough iostat speaks of kilobytes (kB),  megabytes  (MB)...,  it  actually  uses  kibibytes\n(kiB), mebibytes (MiB)...  A kibibyte is equal to 1024 bytes, and a mebibyte is equal to 1024\nkibibytes.\n\n",
            "subsections": []
        },
        "FILES": {
            "content": "/proc/stat contains system statistics.\n/proc/uptime contains system uptime.\n/proc/diskstats contains disks statistics.\n/sys contains statistics for block devices.\n/proc/self/mountstats contains statistics for network filesystems.\n/dev/disk contains persistent device names.\n\n",
            "subsections": []
        },
        "AUTHOR": {
            "content": "Sebastien Godard (sysstat <at> orange.fr)\n\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "sar(1), pidstat(1), mpstat(1), vmstat(8), tapestat(1), nfsiostat(1), cifsiostat(1)\n\nhttps://github.com/sysstat/sysstat\nhttp://pagesperso-orange.fr/sebastien.godard/\n\nLinux                                      SEPTEMBER 2021                                  IOSTAT(1)",
            "subsections": []
        }
    },
    "summary": "iostat  - Report Central Processing Unit (CPU) statistics and input/output statistics for de‐ vices and partitions.",
    "flags": [
        {
            "flag": "-c",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--compact",
            "arg": null,
            "description": "Don't break the Device Utilization Report into sub-reports so that all the metrics get displayed on a single line."
        },
        {
            "flag": "-d",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--dec",
            "arg": "{",
            "description": "Specify the number of decimal places to use (0 to 2, default value is 2)."
        },
        {
            "flag": "-f",
            "long": null,
            "arg": null,
            "description": "+f directory Specify an alternative directory for iostat to read devices statistics. Option -f tells iostat to use only the files located in the alternative directory, whereas op‐ tion +f tells it to use both the standard kernel files and the files located in the alternative directory to read device statistics. directory is a directory containing files with statistics for devices managed in user‐ space. It may contain: - a \"diskstats\" file whose format is compliant with that located in \"/proc\", - statistics for individual devices contained in files whose format is compliant with that of files located in \"/sys\". In particular, the following files located in directory may be used by iostat: directory/block/device/stat directory/block/device/partition/stat partition files must have an entry in directory/dev/block/ directory, e.g.: directory/dev/block/major:minor --> ../../block/device/partition"
        },
        {
            "flag": "-g",
            "long": null,
            "arg": null,
            "description": "Display statistics for a group of devices. The iostat command reports statistics for each individual device in the list then a line of global statistics for the group dis‐ played as groupname and made up of all the devices in the list. The ALL keyword means that all the block devices defined by the system shall be included in the group."
        },
        {
            "flag": "-g",
            "long": null,
            "arg": null,
            "description": "the group are to be displayed, and not statistics for individual devices in the group."
        },
        {
            "flag": "-h",
            "long": "--pretty",
            "arg": null,
            "description": ""
        },
        {
            "flag": "",
            "long": "--human",
            "arg": null,
            "description": "Print sizes in human readable format (e.g. 1.0k, 1.2M, etc.) The units displayed with this option supersede any other default units (e.g. kilobytes, sectors...) associated with the metrics."
        },
        {
            "flag": "-j",
            "long": null,
            "arg": "UUID",
            "description": "Display persistent device names. Keywords ID, LABEL, etc. specify the type of the per‐ sistent name. These keywords are not limited, only prerequisite is that directory with required persistent names is present in /dev/disk. Optionally, multiple devices can be specified in the chosen persistent name type. Because persistent device names are usually long, option --pretty is implicitly set with this option."
        },
        {
            "flag": "-k",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "-m",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "-N",
            "long": null,
            "arg": null,
            "description": "viewing LVM2 statistics."
        },
        {
            "flag": "-o",
            "long": null,
            "arg": "JSON",
            "description": "Display the statistics in JSON (JavaScript Object Notation) format. JSON output field order is undefined, and new fields may be added in the future."
        },
        {
            "flag": "-p",
            "long": null,
            "arg": null,
            "description": "Display statistics for block devices and all their partitions that are used by the system. If a device name is entered on the command line, then statistics for it and all its partitions are displayed. Last, the ALL keyword indicates that statistics have to be displayed for all the block devices and partitions defined by the system, in‐ cluding those that have never been used. If option -j is defined before this option, devices entered on the command line can be specified with the chosen persistent name type."
        },
        {
            "flag": "",
            "long": "--pretty",
            "arg": null,
            "description": "Make the Device Utilization Report easier to read by a human. The device name will be printed on the right side. The report may also be broken into sub-reports if there are many metrics to display (use --compact option to prevent this)."
        },
        {
            "flag": "-s",
            "long": null,
            "arg": null,
            "description": "screens."
        },
        {
            "flag": "-t",
            "long": null,
            "arg": null,
            "description": "of the STIMEFORMAT environment variable (see below)."
        },
        {
            "flag": "-V",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "-x",
            "long": null,
            "arg": null,
            "description": ""
        },
        {
            "flag": "-y",
            "long": null,
            "arg": null,
            "description": "given interval."
        },
        {
            "flag": "-z",
            "long": null,
            "arg": null,
            "description": "sample period."
        }
    ],
    "examples": [
        "iostat Display a single history since boot report for all CPU and Devices.",
        "Display a continuous device report at two second intervals.",
        "Display six reports at two second intervals for all devices.",
        "Display six reports of extended statistics at two second intervals for devices sda and",
        "sdb.",
        "Display  six  reports  at  two  second intervals for device sda and all its partitions",
        "(sda1, etc.)"
    ],
    "see_also": [
        {
            "name": "sar",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/sar/1/json"
        },
        {
            "name": "pidstat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/pidstat/1/json"
        },
        {
            "name": "mpstat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/mpstat/1/json"
        },
        {
            "name": "vmstat",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/vmstat/8/json"
        },
        {
            "name": "tapestat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/tapestat/1/json"
        },
        {
            "name": "nfsiostat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/nfsiostat/1/json"
        },
        {
            "name": "cifsiostat",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/cifsiostat/1/json"
        }
    ],
    "tldr": {
        "source": "official",
        "description": "Report statistics for devices and partitions.",
        "examples": [
            {
                "description": "Display a report of CPU and disk statistics since system startup",
                "command": "iostat"
            },
            {
                "description": "Display a report of CPU and disk statistics with units converted to megabytes",
                "command": "iostat -m"
            },
            {
                "description": "Display CPU statistics",
                "command": "iostat {{-c|--compact}}"
            },
            {
                "description": "Display disk statistics with disk names (including LVM)",
                "command": "iostat -N"
            },
            {
                "description": "Display extended disk statistics with disk names for device \"sda\"",
                "command": "iostat -xN {{sda}}"
            },
            {
                "description": "Display incremental reports of CPU and disk statistics every 2 seconds",
                "command": "iostat {{2}}"
            }
        ]
    }
}