Keyboard shortcuts

This article provides a list of (not commonly known) default keyboard shortcuts and provides information about user customization.

Standard shortcuts

Kernel (SysRq)

There are several low level shortcuts that are implemented in the kernel via the sysrq key which can be used for debugging and recovering from an unresponsive system. Whenever possible, it is recommended that you use these shortcuts instead of doing a hard shutdown (holding down the power button to completely power off the system).

See Wikipedia:Magic SysRq key for more details.

Enabling

systemd has the sysrq permissions bitmask set to 0x10 by default, which does not allow process signalling or rebooting, among other things. To allow full use of the sysrq key on your system, add kernel.sysrq = 1 to your sysctl configuration. Values greater than 1 can be used to selectively enable sysrq functions; see the Linux kernel documentation for details. If you want to make sure it will be enabled even before the partitions are mounted and in the initrd, then add sysrq_always_enabled=1 to your kernel parameters.

Note that changing the setting through these methods will cause the changes to persist across reboots. If you want to try changing the sysrq settings for just your current session, you can run either sysctl kernel.sysrq=1 or echo "1" > /proc/sys/kernel/sysrq.

There are some obvious security risks involved in fully enabling the sysrq key. In addition to forcing reboots and the like, it can be used to dump the contents of the CPU registers, which could theoretically reveal sensitive information. Since using it requires physical access to the system (unless you go out of your way), most desktop users will probably consider the level of risk acceptable. That said, make sure you fully understand the implications of enabling it and the dynamics of the larger context in which your system is operating before you turn sysrq all the way on.

Rebooting

A common idiom to remember this is "Reboot Even If System Utterly Broken" (also referred to as "REISUB"). Alternatively, think of it as "BUSIER" backwards.

Note: Please be aware that "REISUB" itself is just a mnemonic, not any kind of general recommendation for the key press sequence to take back control of an unresponsive system. You should not blindly press these sequences each time without knowing their actual function as noted below.

Keyboard Shortcut	Description	Code to Enable	Other Functions Enabled
Alt+SysRq+r Unraw	Take control of keyboard back from X.	4	Alt+SysRq+k SAK
Alt+SysRq+e Terminate	Send SIGTERM to all processes, allowing them to terminate gracefully.	64	Alt+SysRq+f OOM kill Alt+SysRq+j Thaw
Alt+SysRq+i Kill	Send SIGKILL to all processes, forcing them to terminate immediately.
Alt+SysRq+s Sync	Flush data to disk.	16	-
Alt+SysRq+u Unmount	Unmount and remount all filesystems read-only.	32	-
Alt+SysRq+b Reboot	Reboot	128	-

For example, to selectively enable just the reboot function, set kernel.sysrq to 128. The whole set of REISUB functions can be enabled by setting it to 244, although this also enables the additional functions listed in the last column of the table. For further documentation, see the sysrq key documentation, and the kernel source file /drivers/tty/sysrq.c.

Killing a memory-hogging process

Alt+SysRq+f can be used to invoke the OOM (out-of-memory) killer without causing a kernel panic if nothing can be killed. The OOM killer uses a set of heuristics to pick whichever relatively non-vital process is using the most memory and kill it. This is very useful to kill a process that is softlocking your system by causing excessive thrashing, such as a runaway browser script, and can alleviate the need for a reboot in many cases. Note that the OOM killer can target a wide variety of processes despite its well-meaning heuristics and can be somewhat unpredictable, so be careful about calling it casually.

Troubleshooting

• If you are using a display manager and after Alt+SysRq+e you are presented with the login screen (or full desktop if autologin is enabled), it is most likely caused by Restart=always directive in the relevant service file. If necessary, edit the unit, however this should not prevent the "REISUB" sequence from working.
• If all the above combinations work except Alt+SysRq+b, try using the contralateral Alt key.
• On laptops that use Fn key to differentiate SysRq from PrtScrn, it may not actually be necessary to use the Fn key (i.e., Alt+PrtSc+letter could work).
• On Lenovo laptops SysRq is often configured as Fn+S. To use it press and hold Alt then press Fn+s, release Fn and s still holding Alt followed by the keys above.
• You may need to press Ctrl along with Alt. So for example, full key shortcut would be Ctrl+Alt+SysRq+b.

Linux console

See Linux console#Keyboard shortcuts.

Xorg and Wayland

Keyboard Shortcut	Description	Notes
Ctrl+Alt+F1, F2, F3, ...	Switch to n-th virtual console	If it does not work, try Ctrl+Alt+Fn+F….
Shift+Insert Mouse Button 2	Paste text from the PRIMARY buffer	By default, Qt maps Shift+Insert to CLIPBOARD instead of the PRIMARY buffer (see e.g. [1]) and Ctrl+Shift+Insert is mapped to the PRIMARY buffer.

Customization

Readline

Readline is a commonly used library for line-editing; it is used for example by Bash, FTP, and many more (see the details of readline package under "Required By" for more examples). It has Emacs-like and vi-like editing modes which can be customized with escape sequences. Default key bindings are listed in readline(3) and the Info documentation.

Zsh

Zsh uses ZLE to link shortcuts to widgets, scripts and commands.

Xorg

See Xorg/Keyboard configuration#Frequently used XKB options for some common shortcuts, that are disabled by default.

When we are in a graphical environment we may want to execute a command when certain key combination is pressed (i.e. bind a command to a keysym). There are multiple ways to do that:

• The most portable way using low level tools, such as acpid. Not all keys are supported, but configuration in uniform way is possible for keyboard keys, power adapter connection and even headphone jack (un)plugging events. It is also difficult to run programs inside X session correctly.
• The universal way using Xorg utilities (e.g. xbindkeys) and eventually your desktop environment or window manager tools.
• The quicker way using a third-party program to do everything in GUI, such as the Gnome Control Center.

sxhkd

A simple X hotkey daemon with a powerful and compact configuration syntax. See sxhkd for details.

actkbd

From actkbd home page:

actkbd^AUR (available in AUR) is a simple daemon that binds actions to keyboard events. It recognises key combinations and can handle press, repeat and release events. Currently it only supports the linux-2.6 evdev interface. It uses a plain-text configuration file which contains all the bindings.

A sample configuration and guide is available here.

xbindkeys

xbindkeys allows advanced mapping of keysyms to actions independently of the Desktop Environment.

Tip: If you find xbindkeys difficult to use, try the graphical manager xbindkeys_config-gtk2^AUR from the AUR.

Desktop environments

• LXDE#Bindings
• Xfce#Keyboard Shortcuts

Window managers

• Fluxbox#Hotkeys
• Openbox#Keybinds

Key binding for X-selection-paste

Users who prefer to work with the keyboard rather than the mouse may benefit from a key binding to the paste operation of the middle mouse button. This is especially useful in a keyboard-centered environment. A workflow example is:

1. In Firefox, select a string you want to google for (with the mouse).
2. Hit Ctrl+k to enter the "search engine" field.
3. Hit F9 to paste the buffer, instead of moving the mouse pointer to the field and middle-click to paste.

Note: Shift+Insert has a similar yet different functionality, see #Xorg: Shift+Insert inserts the clipboard buffer, not the x-selection-paste buffer. In some applications, these two buffers are mirrored.

The method suggested here uses the following three packages::

• xsel to give access to the x-selection-buffer content.
• Xbindkeys to bind a key-stroke to an action.
• xvkbd^AUR to pass the buffer string to the application by emulating keyboard input.

This example binds the x-selection-paste operation to the F9 key:

.xbindkeysrc

"xvkbd -no-jump-pointer -xsendevent -text "\D1`xsel`" 2>/dev/null"
    F9

The "\D1" code prefixes a 100 ms pause to inserting the selection buffer (see the xvkbd home page).

Note: Depending on your X configuration, you may need to drop the -xsendevent argument to xvkbd.

The key codes for keys other than F9 can be determined using xbindkeys -k.

References:

• Pasting X selection (not clipboard) contents with keyboard
• xvkbd home page

XMonad Window Manager

In the xmonad window manager there is a built-in function to paste the x-selection-buffer content. In order to bind that function to a key-stroke (here Insert key) the following configuration can be used:

xmonad.hs

import XMonad.Util.Paste
...
  -- X-selection-paste buffer
  , ((0,                     xK_Insert), pasteSelection) ]

Tips and tricks

• If you like a keyboard-centered workflow, you might also appreciate a tiling window manager.

See also

• Linux Newbie Administrator Guide - Shortcuts and Commands
• The Linux keyboard and console HOWTO