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.\" Debian manual page, has been forwarded upstream
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.TH IOTOP "8" "April 2009"
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.SH NAME
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iotop \- simple top\-like I/O monitor
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.SH SYNOPSIS
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.B iotop
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[\fIOPTIONS\fR]
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.SH DESCRIPTION
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iotop watches I/O usage information output by the Linux kernel (requires
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2.6.20 or later) and displays a table of current I/O usage by processes
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or threads on the system. At least the CONFIG_TASK_DELAY_ACCT,
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CONFIG_TASK_IO_ACCOUNTING, CONFIG_TASKSTATS and CONFIG_VM_EVENT_COUNTERS
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options need to be enabled in your Linux kernel build configuration.
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.PP
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iotop displays columns for the I/O bandwidth read and written by each
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process/thread during the sampling period. It also displays the percentage
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of time the thread/process spent while swapping in and while waiting on I/O. For each process, its I/O priority (class/level) is shown.
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.PP
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In addition, the total I/O bandwidth read and written during the sampling
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period is displayed at the top of the interface.
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\fBTotal DISK READ\fR and \fBTotal DISK WRITE\fR values represent total read
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and write bandwidth between processes and kernel threads on the one side and
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kernel block device subsystem on the other. While \fBActual DISK READ\fR and
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\fBActual DISK WRITE\fR values represent corresponding bandwidths for actual
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disk I/O between kernel block device subsystem and underlying hardware (HDD, SSD, etc.).
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Thus \fBTotal\fR and \fBActual\fR values may not be equal at any given moment of time
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due to data caching and I/O operations reordering that take place inside Linux kernel.
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.PP
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Use the left and right arrows to change the sorting, r to reverse the
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sorting order, o to toggle the \-\-only option, p to toggle the \-\-processes option, a to toggle the \-\-accumulated option, q to quit or i to change the priority of a thread or a process' thread(s). Any other key will force a refresh.
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.SH OPTIONS
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.TP
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\fB\-\-version\fR
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Show the version number and exit
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.TP
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\fB\-h\fR, \fB\-\-help\fR
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Show usage information and exit
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.TP
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\fB\-o\fR, \fB\-\-only\fR
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Only show processes or threads actually doing I/O, instead of showing all processes or threads. This can be dynamically toggled by pressing o.
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.TP
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\fB\-b\fR, \fB\-\-batch\fR
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Turn on non\-interactive mode.
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Useful for logging I/O usage over time.
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.TP
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\fB\-n\fR NUM, \fB\-\-iter\fR=\fINUM\fR
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Set the number of iterations before quitting (never quit by default).
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This is most useful in non\-interactive mode.
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.TP
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\fB\-d\fR SEC, \fB\-\-delay\fR=\fISEC\fR
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Set the delay between iterations in seconds (1 second by default).
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Accepts non-integer values such as 1.1 seconds.
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.TP
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\fB\-p\fR PID, \fB\-\-pid\fR=\fIPID\fR
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A list of processes/threads to monitor (all by default).
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.TP
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\fB\-u\fR USER, \fB\-\-user\fR=\fIUSER\fR
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A list of users to monitor (all by default)
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.TP
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\fB\-P\fR, \fB\-\-processes\fR
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Only show processes. Normally iotop shows all threads.
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.TP
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\fB\-a\fR, \fB\-\-accumulated\fR
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Show accumulated I/O instead of bandwidth. In this mode, iotop shows the amount of I/O processes have done since iotop started.
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.TP
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\fB\-k\fR, \fB\-\-kilobytes\fR
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Use kilobytes instead of a human friendly unit. This mode is useful when scripting the batch mode of iotop. Instead of choosing the most appropriate unit iotop will display all sizes in kilobytes.
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.TP
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\fB\-t\fR, \fB\-\-time\fR
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Add a timestamp on each line (implies \-\-batch). Each line will be prefixed by the current time.
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.TP
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\fB\-q\fR, \fB\-\-quiet\fR
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suppress some lines of header (implies \-\-batch). This option can be specified up to three times to remove header lines.
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.RS
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.PD 0
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.TP
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.B \-q
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column names are only printed on the first iteration,
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.TP
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.B \-qq
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column names are never printed,
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.TP
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.B \-qqq
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the I/O summary is never printed.
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.PD 1
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.RE
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.SH SEE ALSO
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.BR ionice (1),
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.BR top (1),
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.BR vmstat (1),
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.BR atop (1),
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.BR htop (1)
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.SH AUTHOR
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iotop was written by Guillaume Chazarain.
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.PP
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This manual page was started by Paul Wise for the
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Debian project and is placed in the public domain.
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