I just got a new laptop and had to google again on how to set caps lock key to escape (I’m a Vim user).

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sudo apt-get install dconf-tools
dconf write /org/gnome/desktop/input-sources/xkb-options "['caps:escape']"

To know your options, use the following command:

man xkeyboard-config

(MAN pages are your friend; man is short for manual)

You can also now use the Dconf GUI editor if you must (SHAME! ;) )

Type Dconf in Unity or Gnome app opener and go to the following location:

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`org` →- `gnome` → `desktop` →  `input-sources` →  `xkb-options`

Add ['caps:escape'] to Custom Value textbox.

dconf caps lock to escape

Cheers.