Section: Maintenance Commands (8)
Updated: February 2002
gpm - a cut and paste utility and mouse server for virtual consoles
This package tries to be a useful
mouse server for applications running on the Linux console. It is
based on the "selection" package, and some of its code
comes from selection itself. This package is intended as a replacement
for "selection" as a cut-and-paste mechanism; it also provides
additional facilities. The "selection"
package offered the first cut-and-paste implementation for Linux using
two mouse buttons, and the cut buffer is still called "selection buffer"
or just "selection" throughout this document.
The information below is extracted from the texinfo file, which is the
preferred source of information.
The gpm executable is meant to act like a daemon (thus, gpmd
would be a better name for it). This section is meant to describe the
command-line options for gpm, while its internals are outlined in
the next section.
Due to restrictions in the ioctl(TIOCLINUX) system call, gpm must
be run by the superuser. The restrictions have been added in the last 1.1
kernels to fix a security hole related to selection and screen dumping.
The server can be configured to match the user's taste, and any
application using the mouse will inherit the server's
attitude. From release 1.02 up to 1.19.2 is was possible
for any user logged on the system console to change the mouse feeling
using the -q option. This is no longer possible for security
As of 0.97 the server program puts itself in the background. To kill
gpm you can just reinvoke it with the -k cmdline switch,
although killall gpm can be a better choice.
Version 1.10 adds the capability to execute special commands on
certain circumstances. Special commands default to rebooting and halting
the system, but the user can specify his/her personal choice. The
capability to invoke commands using the mouse is a handy one for
programmers, because it allows to issue a clean shutdown when the
keyboard is locked and no network is available to restore the system to
a sane state.
Special commands are toggled by triple-clicking the left and right button --
an unlikely event during normal mouse usage. The easiest way to triple-click
is pressing one of the buttons and triple-click the other one. When special
processing is toggled, a message appears on the console (and the speaker
beeps twice, if you have a speaker); if the user releases all the buttons
and presses one of them again within three seconds, then the special
command corresponding to the button is executed.
The default special commands are:
- left button
Reboot the system by signalling the init process
- middle button (if any)
Execute /sbin/shutdown -h now
- right button
Execute /sbin/shutdown -r now
The -S command line switch enables special command processing and
allows to change the three special commands. To accept the default
commands use -S "" (i.e., specify an empty argument). To specify
your own commands, use a colon-separated list to specify commands
associated to the left, middle and right button. If any of the commands
is empty, it is interpreted as `send a signal to the init process'. This
particular operation is supported, in addition to executing external
commands, because sometimes bad bugs put the system to the impossibility
to fork; in these rare case the programmer should be able to shutdown
the system anyways, and killing init from a running process is the only
way to do it.
As an example, -S ":telinit 1:/sbin/halt", associates killing
init to the left button, going single user to the middle one, and halting
the system to the right button.
System administrators should obviously be careful about special
commands, as gpm runs with superuser permissions. Special commands are
best suited for computers whose mouse can be physically accessed only by
COMMAND LINE OPTIONS
Available command line options are the following:
- -a accel
Set the acceleration value used when a single motion event is
longer than delta (see -d).
Start up with selection pasting disabled. This is intended as a
security measure; a plausible attack on a system seems to be to
stuff a nasty shell command into the selection buffer
(rm -rf /) including the terminating line break, then all the
victim has to do is click the middle mouse button ..
As of version 1.17.2, this has developed
into a more general aging mechanism; the
gpm daemon can disable (age) selection pasting
automatically after a period of inactivity. To enable this mode
just give the optional limit parameter (no space in between !)
which is interpreted as the time in seconds for which a selection is
considered valid and pastable.
As of version 1.15.7, a trivial program called
disable-paste is provided. The following makes a good
addition to /etc/profile if you allow multiple users to
work on your console.
case $( /usr/bin/tty ) in
/dev/tty[0-9]*) /usr/bin/disable-paste ;;
- -b baud
Set the baud rate.
- -B sequence
Set the button sequence. 123 is the
normal sequence, 321 can be used by left-handed people,
and 132 can be useful with two-button mice (especially within
Emacs). All the button permutations are allowable.
- -d delta
Set the delta value. When a single motion event
is longer than delta, accel is used as a multiplying
factor. (Must be 2 or above)
Do not automatically enter background operation when started,
and log messages to the standard error stream, not the syslog
mechanism. This is useful for debugging; in previous releases
it was done with a compile-time option.
- -g number
With glidepoint devices, emulate the specified button with tapping.
number must be 1, 2, or 3, and refers to the
button number before the -B button remapping is performed.
This option applies to the mman and ps2 decoding. No button is
emulated by default because the ps2 tapping is incompatible with
some normal ps2 mice
Print a summary of command line options.
- -i interval
Set interval to be used as an upper time limit
for multiple clicks. If the interval between button-up and
button-down events is less than limit, the press is considered
a double or triple click. Time is in milliseconds.
Kill a running gpm. This can be used by busmouse users to kill gpm
before running X (unless they use -R or the single-open
limitation is removed from the kernel).
- -l charset
Choose the inword() look up table. The
charset argument is a list of characters. - is used to
specify a range and \ is used to escape the next character
or to provide octal codes.
Only visible character can appear in charset because control
characters can't appear in text-mode video memory, whence selection
- -m filename
Choose the mouse file to open. Must be before -t and -o.
Enable multiple mode. The daemon will read two different mouse devices.
Any subsequent option will refer to the second device, while any
preceding option will be used for the first device. This option
automatically forces the repeater (-R) option on.
- -o list-of-extra-options
The option works similary to the ``-o'' option of mount; it is
used to specify a list of ``extra options'' that are specific
to each mouse type. The list is comma-separated. The options
dtr, rts or both are used by the serial
initialization to toggle the modem lines like, compatibly with
earlier gpm versions; note however that using -o dtr
associated with non-plain-serial mouse types may now generate
And by the way, use -o after -m and after -t.
Forces the pointer to be visible while selecting. This is the
behaviour of selection-1.7, but it is sometimes confusing.
The default is not to show the pointer, which can be confusing as well.
- -r number
Set the responsiveness. A higher responsiveness is used for a faster
Causes gpm to act as a repeater: any mouse data received while
in graphic mode will be produced on the fifo /dev/gpmdata
in protocol name, given as an optional argument (no space in
between !). In principle, you can use the same
names as for the -t option, although repeating into some
protocols may not be implemented for a while.
In addition, you can specify raw as the name, to repeat
the mouse data byte by byte, without any protocol translation.
If name is omitted, it defaults to msc.
Using gpm in repeater mode, you can configure the X
server to use its fifo as a mouse device. This option is useful for
bus-mouse owners to override the single-open limitation. It is also
an easy way to manage those stupid dual-mode mice which force you
to keep the middle button down while changing video mode. The option
is forced on by the -M option.
- -s number
Set the sample rate for the mouse device.
- -S commands
Enable special-command processing, and optionally specify custom
commands as a colon-separated list. See above for a detailed
description of special commands.
- -t name
Set the mouse type. Use -t help to get a list
of allowable types. Since version 1.18.1, the list also shows
which protocols are available as repeaters (see -R above),
by marking them with an asterisk (``*'').
Use -t after you selected the mouse device with -m.
Print version information and exit.
Force two buttons. This means that the middle button, if any,
will be taken as it was the right one.
Force three buttons. By default the
mouse is considered to be a 2-buttons one, until the middle button
is pressed. If three buttons are there, the right one is used
to extend the selection, and the middle one is used to paste it.
Beware: if you use the -3 option with a 2-buttons mouse, you
won't be able to paste the selection.
To select text press the left mouse button and drag the mouse.
To paste text in the same or another console, press the middle button.
The right button is used to extend the selection, like in `xterm'.
Two-button mice use the right button to paste text.
Double and triple clicks select whole word and whole lines. Use of
the `-p' option is recommended for best visual feedback.
If a trailing space after the contents of a line is highlighted, and if
there is no other text on the remainder of the line, the rest of the
line will be selected automatically. If a number of lines are selected,
highlighted trailing spaces on each line will be removed from the
Any output on the virtual console holding the selection will clear the
highlighted selection from the screen, to maintain integrity of the
display, although the contents of the paste buffer will be unaffected.
The selection mechanism is disabled if the controlling virtual console
is placed in graphics mode, for example when running X11, and is
re-enabled when text mode is resumed. (But see BUGS section below.)
The gpm server may have problems interacting with X: if your
mouse is a single-open device (i.e. a bus mouse), you should kill
gpm before starting X, or use the -R option (see
above). To kill gpm just invoke gpm -k. This problem doesn't
apply to serial mice.
Two instances of gpm can't run on the same system. If you have two mice use
the -M option (see above).
While the current console is in graphic mode, gpm sleeps until
text mode is back (unless -R is used). Thus, it won't reply to
clients. Anyways, it is unlikely that mouse-eager clients will spur
out in hidden consoles.
The clients shipped out with gpm are not updated, thus there are potential
security risks when using them.
Andrew Haylett <email@example.com> (the original selection code)
Ian Zimmerman <firstname.lastname@example.org> (old maintainer)
Alessandro Rubini <email@example.com> (old maintainer (still helps a lot))
Nico Schottelius <firstname.lastname@example.org> (maintainer)
Many many contributors, to both selection and gpm.
The current maintainer is Nico Schottelius. But without the help of
Alessandro Rubini and the mailing list it would be impossible for me to
maintain gpm. The development mailing list can be reached under
email@example.com. More information on the list is in the README file part of
the source distribution of gpm.
/run/gpm.pid The PID of the running gpm
/dev/gpmctl A control socket for clients
/dev/gpmdata The fifo written to by a repeater (`-R') daemon.
mev(1) A sample client for the gpm daemon.
gpm-types(7) Description of mouse types supported by gpm.
The info file about `gpm', which gives more complete information and
explains how to write a gpm client.