On Thu, Sep 21, 2017 at 11:12:19AM -0400, Renaud (Ron) OLGIATI wrote:
> Under Debian, I could su to root in a console, and launch gparted from the CLI.
>
> Now, I get:
>
> ron@ron:~/Desktop $ su
> Password:
> No protocol specified
> xmodmap: unable to open display ':0.0'
> No protocol specified
> xmodmap: unable to open display ':0.0'
> No protocol specified
> xmodmap: unable to open display ':0.0'
> No protocol specified
> xmodmap: unable to open display ':0.0'
> No protocol specified
> xmodmap: unable to open display ':0.0'
> No protocol specified
> xmodmap: unable to open display ':0.0'
>
> root@ron:/home/ron/Desktop # gparted
> No protocol specified
>
> (gpartedbin:4721): Gtk-WARNING **: cannot open display: :0.0
>
> What did I do wrong ?
>
> And by the way, logging in under xdm (?) I had a shock when the Debian name and loogo appeared on the login screen...
>

you probably just need to `xhost +` from the "regular" user account
before su-ing. By default the current display is not accessible by any
user except the one who launched it. root is not an exception.

My2Cents

KatolaZ

-- 
[ ~.,_  Enzo Nicosia aka KatolaZ - GLUGCT -- Freaknet Medialab  ]  
[     "+.  katolaz [at] freaknet.org --- katolaz [at] yahoo.it  ]
[       @)   http://kalos.mine.nu ---  Devuan GNU + Linux User  ]
[     @@)  http://maths.qmul.ac.uk/~vnicosia --  GPG: 0B5F062F  ] 
[ (@@@)  Twitter: @KatolaZ - skype: katolaz -- github: KatolaZ  ]