To temporarily change a console’s keyboard mapping there’s loadkeys, a little user space program that allows you to alter the kernel’s keyboard mapping.
Loading the very handy US International keyboard layout, use

# loadkeys us-intl

To list the currently used keyboard layout or all available keyboard layouts, localectl can be used

# localectl status
   System Locale: LANG=en_US.UTF-8
       VC Keymap: us-altgr-intl
      X11 Layout: us
# localectl list-keymaps
[...]

If localectl is not available, keyboard mapping files are usually found at /lib/kbd/keymaps/xkb/ (e.g. Fedora) or /usr/share/kbd/keymaps/ (e.g. Arch Linux).

To permanently change the default keyboard layout system-wide, alter /etc/vconsole accordingly

KEYMAP="us-altgr-intl"
FONT="eurlatgr"