Cfxtrjtrk

I know how to create shortcuts by Keyboard>shortcuts ...

How to do it from terminal?

I am interested on the existing shortcuts from keyboard>shortcuts.

16.04

The broad answer is the following.
According to the contents of gschema.xml files with definitions of default GSettings they are defined in:

$ gsettings list-recursively | egrep "Alt|Shift|Super|Space|Win|Meta|Primary|Control|Ctrl|Tab" | grep org.gnome | awk '{print $1}' | sort -u

org.gnome.Charmap.WindowState

org.gnome.desktop.wm.keybindings

org.gnome.desktop.wm.preferences

org.gnome.metacity.keybindings

org.gnome.mutter

org.gnome.mutter.keybindings

org.gnome.mutter.wayland.keybindings

org.gnome.settings-daemon.plugins.media-keys

The defaults are the following:

$ gsettings list-recursively | egrep "Alt|Shift|Super|Space|Win|Meta|Primary|Control|Ctrl|Tab" | grep org.gnome

org.gnome.settings-daemon.plugins.media-keys logout '<Control><Alt>Delete'

org.gnome.settings-daemon.plugins.media-keys screenreader '<Alt><Super>s'

org.gnome.settings-daemon.plugins.media-keys window-screenshot '<Alt>Print'

org.gnome.settings-daemon.plugins.media-keys terminal '<Primary><Alt>t'

org.gnome.settings-daemon.plugins.media-keys screenshot-clip '<Ctrl>Print'

org.gnome.settings-daemon.plugins.media-keys magnifier '<Alt><Super>8'

org.gnome.settings-daemon.plugins.media-keys magnifier-zoom-in '<Alt><Super>equal'

org.gnome.settings-daemon.plugins.media-keys video-out '<Super>p'

org.gnome.settings-daemon.plugins.media-keys window-screenshot-clip '<Ctrl><Alt>Print'

org.gnome.settings-daemon.plugins.media-keys area-screenshot-clip '<Ctrl><Shift>Print'

org.gnome.settings-daemon.plugins.media-keys magnifier-zoom-out '<Alt><Super>minus'

org.gnome.settings-daemon.plugins.media-keys screencast '<Ctrl><Shift><Alt>R'

org.gnome.settings-daemon.plugins.media-keys screensaver '<Control><Alt>l'

org.gnome.settings-daemon.plugins.media-keys area-screenshot '<Shift>Print'

org.gnome.desktop.wm.preferences mouse-button-modifier '<Alt>'

org.gnome.mutter.keybindings toggle-tiled-right ['<Primary><Super>Right', '<Super>Right']

org.gnome.mutter.keybindings toggle-tiled-left ['<Primary><Super>Left', '<Super>Left']

org.gnome.settings-daemon.plugins.media-keys logout '<Control><Alt>Delete'

org.gnome.settings-daemon.plugins.media-keys screenreader '<Alt><Super>s'

org.gnome.settings-daemon.plugins.media-keys window-screenshot '<Alt>Print'

org.gnome.settings-daemon.plugins.media-keys terminal '<Primary><Alt>t'

org.gnome.settings-daemon.plugins.media-keys screenshot-clip '<Ctrl>Print'

org.gnome.settings-daemon.plugins.media-keys magnifier '<Alt><Super>8'

org.gnome.settings-daemon.plugins.media-keys magnifier-zoom-in '<Alt><Super>equal'

org.gnome.settings-daemon.plugins.media-keys video-out '<Super>p'

org.gnome.settings-daemon.plugins.media-keys window-screenshot-clip '<Ctrl><Alt>Print'

org.gnome.settings-daemon.plugins.media-keys area-screenshot-clip '<Ctrl><Shift>Print'

org.gnome.settings-daemon.plugins.media-keys magnifier-zoom-out '<Alt><Super>minus'

org.gnome.settings-daemon.plugins.media-keys screencast '<Ctrl><Shift><Alt>R'

org.gnome.settings-daemon.plugins.media-keys screensaver '<Control><Alt>l'

org.gnome.settings-daemon.plugins.media-keys area-screenshot '<Shift>Print'

org.gnome.mutter.wayland.keybindings switch-to-session-10 ['<Primary><Alt>F10']

org.gnome.mutter.wayland.keybindings switch-to-session-11 ['<Primary><Alt>F11']

org.gnome.mutter.wayland.keybindings switch-to-session-12 ['<Primary><Alt>F12']

org.gnome.mutter.wayland.keybindings switch-to-session-1 ['<Primary><Alt>F1']

org.gnome.mutter.wayland.keybindings switch-to-session-2 ['<Primary><Alt>F2']

org.gnome.mutter.wayland.keybindings switch-to-session-3 ['<Primary><Alt>F3']

org.gnome.mutter.wayland.keybindings switch-to-session-4 ['<Primary><Alt>F4']

org.gnome.mutter.wayland.keybindings switch-to-session-5 ['<Primary><Alt>F5']

org.gnome.mutter.wayland.keybindings switch-to-session-6 ['<Primary><Alt>F6']

org.gnome.mutter.wayland.keybindings switch-to-session-7 ['<Primary><Alt>F7']

org.gnome.mutter.wayland.keybindings switch-to-session-8 ['<Primary><Alt>F8']

org.gnome.mutter.wayland.keybindings switch-to-session-9 ['<Primary><Alt>F9']

org.gnome.metacity.keybindings toggle-tiled-right ['<Super>Right']

org.gnome.metacity.keybindings toggle-tiled-left ['<Super>Left']

org.gnome.desktop.wm.keybindings cycle-windows-backward ['<Shift><Alt>Escape']

org.gnome.desktop.wm.keybindings minimize ['<Primary><Alt>KP_0']

org.gnome.desktop.wm.keybindings move-to-monitor-left ['<Super><Shift>Left']

org.gnome.desktop.wm.keybindings unmaximize ['<Primary><Super>Down', '<Super>Down', '<Alt>F5']

org.gnome.desktop.wm.keybindings panel-main-menu ['<Super>s', '<Alt>F1']

org.gnome.desktop.wm.keybindings cycle-windows ['<Alt>Escape']

org.gnome.desktop.wm.keybindings cycle-panels-backward ['<Shift><Control><Alt>Escape']

org.gnome.desktop.wm.keybindings panel-run-dialog ['<Alt>F2']

org.gnome.desktop.wm.keybindings switch-to-workspace-down ['<Control><Alt>Down']

org.gnome.desktop.wm.keybindings move-to-corner-ne ['<Primary><Alt>KP_Prior']

org.gnome.desktop.wm.keybindings move-to-side-e ['<Primary><Alt>KP_Right']

org.gnome.desktop.wm.keybindings move-to-workspace-right ['<Control><Shift><Alt>Right']

org.gnome.desktop.wm.keybindings move-to-workspace-up ['<Shift><Control><Alt>Up']

org.gnome.desktop.wm.keybindings maximize ['<Primary><Super>Up', '<Super>Up', '<Primary><Alt>KP_5']

org.gnome.desktop.wm.keybindings cycle-group-backward ['<Shift><Alt>F6']

org.gnome.desktop.wm.keybindings move-to-side-n ['<Primary><Alt>KP_Up']

org.gnome.desktop.wm.keybindings move-to-side-s ['<Primary><Alt>KP_Down']

org.gnome.desktop.wm.keybindings move-to-side-w ['<Primary><Alt>KP_Left']

org.gnome.desktop.wm.keybindings move-to-corner-nw ['<Primary><Alt>KP_Home']

org.gnome.desktop.wm.keybindings begin-move ['<Alt>F7']

org.gnome.desktop.wm.keybindings move-to-monitor-down ['<Super><Shift>Down']

org.gnome.desktop.wm.keybindings move-to-workspace-left ['<Control><Shift><Alt>Left']

org.gnome.desktop.wm.keybindings move-to-corner-se ['<Primary><Alt>KP_Next']

org.gnome.desktop.wm.keybindings activate-window-menu ['<Alt>space']

org.gnome.desktop.wm.keybindings switch-input-source ['<Super>space']

org.gnome.desktop.wm.keybindings move-to-monitor-right ['<Super><Shift>Right']

org.gnome.desktop.wm.keybindings switch-input-source-backward ['<Shift><Super>space']

org.gnome.desktop.wm.keybindings move-to-workspace-last ['<Super><Shift>End']

org.gnome.desktop.wm.keybindings cycle-panels ['<Control><Alt>Escape']

org.gnome.desktop.wm.keybindings move-to-monitor-up ['<Super><Shift>Up']

org.gnome.desktop.wm.keybindings move-to-corner-sw ['<Primary><Alt>KP_End']

org.gnome.desktop.wm.keybindings toggle-shaded ['<Primary><Alt>s']

org.gnome.desktop.wm.keybindings switch-to-workspace-1 ['<Super>Home']

org.gnome.desktop.wm.keybindings switch-panels ['<Control><Alt>Tab']

org.gnome.desktop.wm.keybindings switch-panels-backward ['<Shift><Control><Alt>Tab']

org.gnome.desktop.wm.keybindings switch-applications-backward ['<Shift><Super>Tab', '<Shift><Alt>Tab']

org.gnome.desktop.wm.keybindings show-desktop ['<Primary><Super>d', '<Primary><Alt>d', '<Super>d']

org.gnome.desktop.wm.keybindings switch-applications ['<Super>Tab', '<Alt>Tab']

org.gnome.desktop.wm.keybindings switch-to-workspace-left ['<Control><Alt>Left']

org.gnome.desktop.wm.keybindings toggle-maximized ['<Primary><Alt>KP_5']

org.gnome.desktop.wm.keybindings begin-resize ['<Alt>F8']

org.gnome.desktop.wm.keybindings move-to-workspace-down ['<Shift><Control><Alt>Down']

org.gnome.desktop.wm.keybindings switch-to-workspace-last ['<Super>End']

org.gnome.desktop.wm.keybindings switch-group-backward ['<Shift><Super>Above_Tab', '<Shift><Alt>Above_Tab']

org.gnome.desktop.wm.keybindings switch-group ['<Super>Above_Tab', '<Alt>Above_Tab']

org.gnome.desktop.wm.keybindings cycle-group ['<Alt>F6']

org.gnome.desktop.wm.keybindings close ['<Alt>F4']

org.gnome.desktop.wm.keybindings switch-to-workspace-up ['<Control><Alt>Up']

org.gnome.desktop.wm.keybindings move-to-workspace-1 ['<Super><Shift>Home']

org.gnome.desktop.wm.keybindings switch-to-workspace-right ['<Control><Alt>Right']

org.gnome.mutter overlay-key 'Super_L'

org.gnome.mutter.keybindings toggle-tiled-right ['<Primary><Super>Right', '<Super>Right']

org.gnome.mutter.keybindings toggle-tiled-left ['<Primary><Super>Left', '<Super>Left']

So you can set any of them with gsettings set:

gsettings set org.gnome.settings-daemon.plugins.media-keys logout "'<Control><Alt>Delete'"

or reset with

gsettings reset org.gnome.settings-daemon.plugins.media-keys logout

Note: unity-control-center keyboard uses <Primary> for <Ctrl>.