I recently found out you can use xinput to enable or disable an input device. I used to use synclient to disable my touchpad, or using this tricky way to disable my laptop keyboard.

The first step to get device name or id of the device:

% xinput list
 Virtual core pointer                          id=2    [master pointer  (3)]
    Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
    USB Optical Mouse                         id=8    [slave  pointer  (2)]
    SynPS/2 Synaptics TouchPad                id=7    [slave  pointer  (2)]
 Virtual core keyboard                         id=3    [master keyboard (2)]
     Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
     Sleep Button                              id=9    [slave  keyboard (3)]
     Power Button                              id=10   [slave  keyboard (3)]
     Video Bus                                 id=11   [slave  keyboard (3)]
     AT Translated Set 2 keyboard              id=6    [slave  keyboard (3)]

For touchpad, the device name is 'SynPS/2 Synaptics TouchPad' and id is 7; for keyboard, they are 'AT Translated Set 2 keyboard' and 6. Next step is to know the properties of a device:

% xinput list-props 'AT Translated Set 2 keyboard'
Device 'AT Translated Set 2 keyboard':
        Device Enabled (127):   1

This keyboard only has a property 'Device Enabled' whose value is 1, that means this keyboard is enabled. To test disabling:

sleep 0.1 ; xinput set-prop 'AT Translated Set 2 keyboard' 'Device Enabled' 0 ; sleep 5 ; xinput set-prop 'AT Translated Set 2 keyboard' 'Device Enabled' 1

The first sleep 0.1 is to prevent enter keypress being repeatedly sent somehow when you directly disable the keyboard, I am guessing when you hit the enter and the command is executed, meaning the keyboard is disabled, but the keyup event is not yet sent, so X still thinks the enter key is pressed down.

Another simple way is to use id, so you dont need long device name:

sleep 0.1 ; xinput set-prop 8 127 0 ; sleep 5 ; xinput set-prop 8 127 1

8 is id of this keyboard and 127 is the property id of 'Device Enabled'. When you list properties of device using list-props, the numbers after property names are the property ids. It seems that 'Device Enabled' always has id 127, but device id is not always the same. It depends on device attached time, who shows up first who gets next available id.

One more thing to note: I dont need root privilege to set property value.