Re: Why emacs touches read-only file?

[bojohan+news@dd.chalmers.se (Johan Bockgård)]

Daniel <hanmoai@gmail.com> writes:

> I am running it as root,

That's why.

> but the permission is read-only to root also.

The behavior was changed in Emacs 22. From etc/NEWS:

    *** When you are root, and you visit a file whose modes specify
    read-only, the Emacs buffer is now read-only too. Type C-x C-q if
    you want to make the buffer writable. (As root, you can in fact
    alter the file.)

And the corresponding antinews[1] entry:

   * When you are logged in as root, all files now give you writable
     buffers, reflecting the fact that you can write any files.


[1] "For those users who live backwards in time, here is information
  about downgrading to Emacs version 21.4."
  (info "(emacs)Antinews")

-- 
Johan Bockgård