How can I use the function debian-run-directories in Ubuntu 18?

Question

I had this code in my emacs config to load/include any additional config in the site-start.d folder. It worked well on two debian machines, but currently I need to use Ubuntu 18 with emacs 26.3 and it fails.

(setq dotfiles-dir (file-name-directory (or load-file-name (buffer-file-name))))          
(let ((user-site-start-dir (concat dotfiles-dir "/site-start.d")))                        
     (debian-run-directories user-site-start-dir))

From a related answer at https://stackoverflow.com/a/27676611 I understood it is both available in debian and Ubuntu. The error I get on start is:

Warning (initialization): An error occurred while loading ‘/home/foo/.emacs.d/init.el’:

Symbol's function definition is void: debian-run-directories

What is the easiest way to use it in Ubuntu?

Answer 1

Ubuntu 18.04 does not have emacs 26 in its repositories, so it has been installed from source or from a ppa that doesn't include the debian patches.

The function debian-run-directories is defined in debian-startup.el that is part of the emacsen-common package, you can install it with

sudo apt install emacsen-common

After the package installation you may need to add /usr/share/emacs/site-lisp/ to load-path before loading debian-startup.el.

(add-to-list 'load-path "/usr/share/emacs/site-lisp")
(load "debian-startup")