Reopen a buffer as root prompting for password if necessary

(defun find-alternative-file-with-sudo ()
    "Open current buffer as root!"
    (interactive)
    (when buffer-file-name
      (find-alternate-file
       (concat "/sudo:root@localhost:"
               buffer-file-name))))

  (global-set-key (kbd "C-x C-r") 'find-alternative-file-with-sudo)

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