Control: forwarded -1

On 2018-08-10 01:09:13 -0500, Rob Browning wrote:
> Vincent Lefevre <> writes:
> > "su -l" is not a solution as it reset the current working directory.
> > And one should still be able to run X applications after su.
> Hmm, is that true?

    -, -l, --login
        Start  the shell as a login shell with an environment similar to
        a real login:

           o      clears all the environment variables except TERM

           o      initializes the  environment  variables  HOME,  SHELL,
                  USER, LOGNAME, and PATH

           o      changes to the target user's home directory

           o      sets  argv[0] of the shell to '-' in order to make the
                  shell a login shell

The fact that it clears all the environment variables except TERM.
The fact that the LC_* environment variables are cleared may be
annoying too. BTW, there is no guarantee that TERM will still work
if TERMINFO is cleared! I sometimes use a user-defined TERM, so
that keeping TERMINFO is important in that case.

> I don't actually know, but the suggestion I'd often
> heard is to generally avoid running X applications much as root, but if
> I were going to, I'd use "su -", which (now that I look) does appear to
> handle at least XAUTHORITY -- though I'd still be wary.

As you can see above, XAUTHORITY is cleared too.

I also avoid running X applications, except Emacs.

> > But in any case, emacs shouldn't create files/directories if the
> > user hasn't explicitly asked it to do that.
> I'd expect emacs to create various files via gtk, dbus, and other
> subsystems it uses, and it's certainly going to create bits like
> ~/.emacs and ~/.emacs.d if it needs to (for M-x customize, etc.).

I don't use M-x customize, certainly not as root. If the user doesn't
modify his configuration, there is no need to create such files.
Anyway, for ~/.emacs and ~/.emacs.d, there are no problems since
HOME is set to one for the target user, e.g. to "/root" (unless
-m or -p is used, but I've said that I do not use them).

> Whether or not it's doing it correctly is another question, but I'm not
> at all surprised that plain "su" with an X-based emacs frame (i.e. not
> "emacs -nw") has trouble.

Historically, there had never been any problem. AFAIK, it was assumed
that the only files that could be created automatically (e.g. caches)
would be under $HOME, but HOME is set to one for the target user,
avoiding issues.

The same bug was reported here against Fedora 25:

and was closed a few years later due to Fedora 25 EOL.

I've also just seen

but this may be different as this is related to desktop environments
(potentially a more complex case to decide what to do).

> If you want to pursue this, I suspect you should pursue it upstream,
> or I'll plan to forward it later if you prefer.

I've just reported a bug upstream:

Vincent Lefèvre <> - Web: <>
100% accessible validated (X)HTML - Blog: <>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

Reply via email to