IOSTAT(8)

💅 IOSTAT(8) 💅

okay bestie, welcome to the System Manager's Manual page for iostat, the utility that reports I/O statistics. yes, we're doing kernel stats and we're doing them cute. 🫶

🌸 NAME 🌸

iostat — report I/O statistics. literally that's the name, that's the job. ✨

🦋 SYNOPSIS 🦋

iostat [-CUdKIoT?] [-c count] [-n devs] [-w wait] [drives]

💖 DESCRIPTION 💖

okay so the iostat utility displays kernel I/O statistics on terminal, device and cpu operations. the first statistics that are printed are averaged over the system uptime. to get info about the current activity, a suitable wait time should be specified, so that the subsequent sets of printed statistics will be averaged over that time. periodt. ⏳

✨ the options, bestie (all of them) ✨

The options are as follows:

• -? — display a usage statement and exit. no notes, just vibes.
• -c — repeat the display count times. if no wait interval is specified, the default is 1 second. ⏰
• -C — display CPU statistics. this is on by default, unless -d is specified. main character CPU energy. 👑
• -d — display only device statistics. if this flag is turned on, only device statistics will be displayed, unless -C or -U or -T is also specified to enable the display of CPU, load average or TTY statistics. so -d is not the boss of -C, -U, or -T, iykyk. 💀
• -I — display total statistics for a given time period, rather than average statistics for each second during that time period. total slay, not per-second slay. ✨
• -K — in the blocks transferred display (-o), display block count in kilobytes rather than the device native block size. 💖
• -n — display up to devs number of devices. the iostat utility will display fewer devices if there are not devs devices present. respect the limit, bestie. 🛑
• -o — display old-style iostat device statistics. sectors per second, transfers per second, and milliseconds per seek are displayed. if -I is specified, total blocks/sectors, total transfers, and milliseconds per seek are displayed. vintage but make it useful. 🎀
• -T — display TTY statistics. this is on by default, unless -d is specified. TTY bestie stays included. 🧚
• -U — display system load averages. this is on by default, unless -d is specified. load average said hi. 🌈
• -w — pause wait seconds between each display. if no repeat count is specified, the default is infinity. infinity seconds? no bestie, infinity displays. 😭

The iostat utility displays its information in the following format:

🖥️ tty

• tin — characters read from terminals
• tout — characters written to terminals

💽 devices

Device operations. the header of the field is the device name and unit number. the iostat utility will display as many devices as will fit in a standard 80 column screen, or the maximum number of devices in the system, whichever is smaller. if -n is specified on the command line, iostat will display the smaller of the requested number of devices, and the maximum number of devices in the system. to force iostat to display specific drives, their names may be supplied on the command line. the iostat utility will not display more devices than will fit in an 80 column screen, unless the -n argument is given on the command line to specify a maximum number of devices to display, or the list of specified devices exceeds 80 columns. if fewer devices are specified on the command line than will fit in an 80 column screen, iostat will show only the specified devices. okay that was a lot of 80-column lore, but we got it. 📏

The standard iostat device display shows the following statistics:

• KB/t — kilobytes per transfer
• tps — transfers per second
• MB/s — megabytes per second

The standard iostat device display, with the -I flag specified, shows the following statistics:

• KB/t — kilobytes per transfer
• xfrs — total number of transfers
• MB — total number of megabytes transferred

The old-style iostat display (using -o) shows the following statistics:

• sps — sectors transferred per second
• tps — transfers per second
• msps — average milliseconds per transaction

The old-style iostat display, with the -I flag specified, shows the following statistics:

• blk — total blocks/sectors transferred
• xfr — total transfers
• msps — average milliseconds per transaction

🧠 cpu

• us — % of cpu time in user mode
• sy — % of cpu time in system mode
• id — % of cpu time in idle mode

🎀 EXAMPLES 🎀

iostat -w 1 disk0 disk2

display statistics for the first and third disk devices device every second ad infinitum. yes bestie, forever. 🔁

iostat -c 2

display the statistics for the first four devices in the system twice, with a one second display interval. two rounds, four devices, one second apart. 💅

iostat -Iw 3

display total statistics every three seconds ad infinitum. total stats, every 3 seconds, forever and ever. 🌟

iostat -odICTw 2 -c 9

display total statistics using the old-style output format 9 times, with a two second interval between each measurement/display. the -d flag generally disables the TTY and CPU displays, but since the -T and -C flags are given, the TTY and CPU displays will be displayed. plot twist: they're back. 😭

🌈 SEE ALSO 🌈

netstat(1), nfsstat(1), ps(1), top(1), vm_stat(1)

The sections starting with “Interpreting system activity” in Installing and Operating 4.3BSD.

⭐ HISTORY ⭐

This version of iostat first appeared in FreeBSD 3.0. iconic. 🕰️

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mwah 💋 this page is from Debian, dated May 22, 2015, and it's the IOSTAT(8) manual. byeee 🫶