Increase the space between lines in vim

linespace is only available for the GUI version, i.e. gVim or MacVim, and not console Vim. So maybe you are trying in your terminal?

'linespace' 'lsp'       number  (default 0, 1 for Win32 GUI)
                        global
                        {not in Vi}
                        {only in the GUI}

If you want to modify the linespacing of your terminal you have to do it in your terminal settings, not in Vim. (Maybe you can do it programmatically in your .vimrc.)

you can' use linespace in terminal mode , it is for GUI only