Date: Fri, 15 May 2009 08:41:54 +0100 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: Pieter Donche <Pieter.Donche@ua.ac.be> Cc: "mail.list freebsd-questions" <freebsd-questions@freebsd.org> Subject: Re: root user, graphical programs Message-ID: <4A0D1CC2.8000107@infracaninophile.co.uk> In-Reply-To: <alpine.BSF.2.00.0905150843110.83166@macos.cmi.ua.ac.be> References: <alpine.BSF.2.00.0905150843110.83166@macos.cmi.ua.ac.be>
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Pieter Donche wrote:
> FreeBSD 7, KDE 3.5
> To install Matlab (in linux compat mode), one must execute the
> matlab install program as root. The installer is graphical.
> When from a KDE terminal window, I switch to root (# su -)
> and try a graphical program, e.g. # xpdf, I get Can't open display.
> The FreeBSD handbook (10.5.1) says in that case type setenv HOME ~USER
> (USER the username where the su command was given). This doesn't help
> I still get Can't open display.
>=20
> What's wrong and how to solve it?
That's the standard X Windows security stopping other users opening windo=
ws
on your screen. In this case, something like:
% xhost +LOCAL:
% su
# {...whatever you need to do to install your app...}
# exit
% xhost -LOCAL:
However be aware of the risks: xhost +LOCAL: means that any other user
of the same machine can access your display and potentially capture any
input including (for instance) the root password.
Hmmm... Actually, a more secure means of doing the same thing, that only
grants access to your display by the local root user would be:
% xauth extract - $DISPLAY > ~/authtoken
% su -
# echo $HOME
(This should return /root -- this is important so that the correct .Xauth=
ority
file gets updated.)
# xauth merge /home/your-uid/authtoken
# rm /home/your-uid/authtoken
# setenv DISPLAY :0.0
# {...whatever you need to do to install your app...}
Now any X programs run by root will open on your display. To revoke this=
permission you can simply remove /root/.Xauthority or for finer grained
control you can use
=20
# xauth remove $DISPLAY
Cheers,
Matthew
--=20
Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard
Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
Kent, CT11 9PW
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