Gain sudo privileges in Emacs without launch it as sudo

.emacs

;; Makes possible to sudo-edit files                                                                        
;; From Damien Cassou                                                                                       
;; https://github.com/renard/dired-toggle-sudo/issues/1                                                     
(defun sudo ()                                                                                              
  (interactive)                                                                                             
  (let ((fname (or buffer-file-name                                                                         
                   dired-directory)))                                                                       
   (when fname                                                                                             
     (if (string-match "^/sudo:root@localhost:" fname)                                                     
         (setq fname (replace-regexp-in-string                                                             
                      "^/sudo:root@localhost:" ""                                                          
                      fname))                                                                              
       (setq fname (concat "/sudo:root@localhost:" fname)))                                                
     (find-alternate-file fname))))

To use from dired-mode, type M-x sudo