Emacs directory is not readable on Ubuntu

Question

When I start Emacs 25 on Ubuntu, I get this message:

cannot open load file permission non accordée , mode-util

With emacs25 -debug I've got:

Warning: Lisp directory '/usr/share/emacs/25.2/lisp': Permission non accordée
Warning: Could not find simple.el or simple.elc

Answer 1

All files under /usr should be world-readable. They're system files that cam be obtained by anyone over the Internet, so there'd be no point in preventing local users from reading them. (There may be exceptions for proprietary software, but even so it is very uncommon to have non-world-readable files under /usr.)

The fact that /usr/share/emacs/25.2/lisp is not world-readable indicates that there is something wrong with your installation. This may be a problem with more than Emacs.

If there are regular files with broken permissions, you can repair the permissions by reinstalling the packages that contain those files with the broken permissions. For example,

dpkg -S /usr/share/emacs/25.2/lisp/simple.elc

outputs

emacs25-common: /usr/share/emacs/25.2/lisp

so reinstalling the permissions on emacs25-common will restore the permissions on this file:

sudo apt-get install --reinstall emacs25-common

However, this doesn't work for directories. To restore the permissions on /usr/share/emacs/25.2/lisp, do it manually:

sudo chown root:root /usr/share/emacs/25.2/lisp
sudo chmod 755 /usr/share/emacs/25.2/lisp

Use ls -ld /path/to/directory to check the permissions and ownership on a directory. There may be other directories with broken permissions.

Answer 2

Check the file permissions on directory /usr/share/emacs/25.2/lisp. It looks like you do not have permission to read from it.

You can see the permissions in Dired (C-x d). If you have sufficient permissions in general (e.g. on the parent directory) then you can change the permissions for that directory using M (command dired-do-chmod) in Dired for the parent directory.