Ubuntu Manpage: iotop - simple top-like I/O monitor

NAME

       iotop - simple top-like I/O monitor

SYNOPSIS

       iotop [OPTIONS]

DESCRIPTION

iotop watches I/O usage information available in the Linux kernel (requires 2.6.20 or later) and displays
a table of current I/O usage by processes or threads on the system. At least the CONFIG_TASK_DELAY_ACCT,
CONFIG_TASK_IO_ACCOUNTING, CONFIG_TASKSTATS and CONFIG_VM_EVENT_COUNTERS options need to be enabled in
your Linux kernel build configuration.

Running iotop as non-root user is possible by adding the NET_ADMIN capability. This can be done by e.g.:

$ sudo setcap 'cap_net_admin+eip' <path-to>/iotop

Be warned that this will also allow other users to run it and get access to information that normally
should not be available to them.

iotop displays columns for the I/O bandwidth read and written by each process/thread during the sampling
period. It also displays the percentage 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.

In addition, the total I/O bandwidth read and written during the sampling period are displayed at the top
of the interface. Total DISK READ and Total DISK WRITE values represent total read and write bandwidth
between processes and kernel threads on one side and kernel block device subsystem on the other. While
Current DISK READ and Current DISK WRITE values represent corresponding bandwidths for current disk I/O
between the kernel block device subsystem and the underlying hardware (HDD, SSD, etc.). Thus Total and
Current values may not be equal at any given moment of time due to data caching and I/O operations
reordering that take place inside the Linux kernel.

Use the left and right arrows to select the sort column, r or space to reverse the sorting order, o to
toggle the --only option (this uses the visible values from the GRAPH column or the IO column in case the
GRAPH column is hidden), p to toggle the --processes option, a to toggle the --accumulated option, i to
change the priority of a thread or a process's thread, f to change filtering by UID/PID (--user and --pid
options), 1-9 to toggle the visibility of the respective column, 0 to show all columns, up/down arrows,
page-up/page-down/home/end keys to scroll and q to quit. Any unrecognized key will be ignored.

All processes or threads that have exited are displayed grayed for the same time as is visible in the
GRAPH column or 3 seconds when it is hidden. The invalid data points in the GRAPHS column are displayed
inverse or with letter x (see option --dead-x and x shortcut). When using unicode characters each
position contains two datapoints and only the positions with two invalid data points are reversed.

It is possible for threads of a process to have different priority from their main process. This is shown
with ! in the PRIO column of the main process as e.g. !be/4.

Threads activity is always aggregated with and shown inside the main process.

When showing threads, they always appear below their main process and are sorted in the same way as the
processes.

There are two ways to change the IO priority of a process or thread - press i and use arrows to select
the process or thread from the visible ones on screen or press i and type its TID (PID and TID have the
same value for the main process). Then use tab and arrows to change the priority value and confirm with
enter. Shortcuts esc or q will cancel this mode.

To change the UID and PID filters, press f and use tab to select the UID or PID field, then type the
numerical id or n to remove the filter and confirm with enter. Filtering is always done by TID because it
is unique. Note that for the main process PID is the same as TID. Shortcuts esc or q will cancel this
mode.

Starting with Linux kernel 5.14.x task_delayacct is configurable at runtime and set to off by default.
This setting can be changed in interactive mode by the Ctrl-T shortcut. In batch mode a warning is
printed when the setting is OFF. From the command line this can be enabled by:

$ sudo sysctl kernel.task_delayacct=1

and disabled again by:

$ sudo sysctl kernel.task_delayacct=0

It is advisable to keep this option off when not using this or another monitoring program because when
enabled it has some effect on system performance.

OPTIONS

-v, --version
Show the version number and exit

-h, --help
Show usage information and exit

-H, --help-type=TYPE
Set the type of interactive help shown. Accepted values for TYPE are none, win and inline.

-o, --only
Only show processes or threads actually doing I/O, instead of showing all processes or threads.
This can be dynamically toggled by pressing o

-b, --batch
Turn on non-interactive mode. Useful for logging I/O usage over time

-n NUM, --iter=NUM
Set the number of iterations before quitting (never quit by default). This is most useful in
non-interactive mode

-d SEC, --delay=SEC
Set the delay between iterations in seconds (1 second by default). Accepts non-integer values
such as 1.1 seconds

-p PID, --pid=PID
A process/thread id to monitor (all by default)

-u USER, --user=USER
A user id to monitor (all by default). The value will always be resolved first unless it is
prefixed by + in which case it is treated as numeric only. Values that do not resolve but appear
to be numeric are used as numeric

-P, --processes
Only show processes. Normally iotop shows processes and all threads

-a, --accumulated
Show accumulated I/O instead of bandwidth. In this mode, iotop shows the amount of I/O processes
have done since iotop started

-k, --kilobytes
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

-t, --time
Add a timestamp on each line (implies --batch). Each line will be prefixed by the current time

-c, --fullcmdline
Show processes' full file path and parameters

-1, --hide-pid
Hide PID/TID column

-2, --hide-prio
Hide PRIO column

-3, --hide-user
Hide USER column

-4, --hide-read
Hide DISK READ column

-5, --hide-write
Hide DISK WRITE column

-6, --hide-swapin
Hide SWAPIN column

-7, --hide-io
Hide IO column

-8, --hide-graph
Hide GRAPH column

-9, --hide-command
Hide COMMAND column

-g TYPE, --grtype=TYPE
Set GRAPH column data source. Accepted values for TYPE are io, r, w, rw and sw.

-q, --quiet
Suppress some lines of header (implies --batch). This option can be specified up to three times to
remove header lines
-q column names are only printed on the first iteration,
-qq column names are never printed,
-qqq the I/O summary is never printed

-x, --dead-x
Show dead processes/threads with letter x instead of inverse background

KEYBOARD SHORTCUTS

       q, Q   Exit

       <space>, r, R
              Toggle sort order

       <home> Scroll to the top of the list

       <end>  Scroll to the bottom of the list

       <page-up>
              Scroll one screen up

       <page-down>
              Scroll one screen down

       <up>   Scroll one line up

       <down> Scroll one line down

       <right>
              Sort by next column

       <left> Sort by previous column

       <esc>  Cancel ionice or filter selection. In case only the help window is open then close it

       o, O   Toggle showing only processes with IO activity

       p, P   Toggle showing processes/threads

       a, A   Toggle showing accumulated/current values

       ?, h, H
              Toggle showing shortcut help

       c, C   Toggle showing full command line

       1, 2, 3, 4, 5, 6, 7, 8, 9
              Toggle showing the column (column number corresponds to the shortcut)

       0      Show all columns

       g, G   Cycle GRAPH source (IO=IO, R=DISK READ , W=DISK WRITE, R+W=DISK READ+DISK WRITE, SW=SWAPIN). Using
              g will cycle forward and G will cycle backward.

       i, I   IOnice a process/thread (depends on process/thread display mode)

       f, F   Change UID and PID filters

       u, U   Toggle using Unicode/ASCII characters for pseudo graph

       x, X   Toggle the display mode of exited processes/threads between letter x and inverse background

       s, S   Toggle freeze of data collection

       Ctrl-T Toggle task_delayacct kernel sysctl

AUTHOR