Questions[pkexec](ubuntu)

Previously it was told that it is bad idea to use sudo to launch GUI-based applications.
So one should use pkexec instead.

I remembered it, so I tried this to launch Kubuntu Driver Manager on Kubuntu 20.04 LTS using terminal as

pkexec kubuntu-driver-manager

But this command does not work, it crashes with the following output:

qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: wayland-org.kde.kwin.qpa, dxcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

Aborted (core dumped)

I have recently reported bug 1885615. But I'm very surprised with this behavior. And what is interesting sudo kubuntu-driver-manager works normally.
I still can launch Gtk-based applications on Kubuntu using pkexec - commands like pkexec pluma results in opening the application with root rights.

So my question is in the title.

when I try to use sudo -I command, I get this error:

sudo: /etc/sudoers is owned by uid 33, should be 0
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

so I tried to use pkexec chown -R root:root /etc/sudoers and I get this error:

polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
==== AUTHENTICATION FAILED ===
Error executing command as another user: Not authorized

This incident has been reported.

Does anyone know what to do with this?

EDIT:

I think it is because I ran sudo chown www-data:www-data / by a mistake, but I stopped it after few seconds.

What do you think, I should do with that?

After the OS is running for a while, it may trigger for a bug that caused pkexec (including any application that use it, including synaptic) to hang. This can only be recovered from relaunching OS or gnome-shell.

This is a screenshot that describe this situation:

xhost +si:localuser:root
pkexec synaptic

I remember the same error in Manjaro with gnome 3.28, it disappeared in gnome 3.30. How do I backport the fix (if there is any) to Ubuntu 18.04?

UPDATE 1

these are my desktop environment:

$ export | grep XDG_SESS
declare -x XDG_SESSION_DESKTOP="ubuntu"
declare -x XDG_SESSION_ID="1"
declare -x XDG_SESSION_TYPE="x11"

... and synaptics version

$ apt-cache policy synaptic
synaptic:
  Installed: 0.84.3ubuntu1
  Candidate: 0.84.3ubuntu1
  Version table:
 *** 0.84.3ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status
peng@peng-ThinkPad-P51s:~$ 

UPDATE 2: it appears that it is caused by an unknown bug in gnome authentication agent, as I switched to XFCE and this problem never happens again, so now the problem becomes: how to get rid of the gnome authentication agent?

I'm trying to be a good boy and stop using gksudo, especially since it just got orphaned in the 18.04 daily builds (note, this question is not specific to 18.04).

In the bad old days of using gksudo, I'd typically navigate to a folder containing the file I wish to edit (I use pcmanfm) then select Tools/Open Current Folder In Terminal from the menu. Then I'd type gksudo leafpad [file-I-wish-to-edit] in the newly opened terminal.

Using information in the very useful answer How to configure pkexec? I set my .bash_aliases and I am able to now type pkexec leafpad [file-I-wish-to-edit] in the newly opened terminal and I don't get any errors. Sadly, though I get a blank file instead of what I wanted. I have determined that this is because leafpad is looking in /root instead of the folder I wished to be in.

How can I maintain my halo, continue to use pkexec instead of gksudo, yet retain the functionality I'm used to?

gksudo seeming to be somehow depreciated since 2017 as I see on the french forum documentation, is there an environment and version agnostic best practice allowing to use gedit as root?

(excluding vim, nano or tee: the use case being a GUI amendment of sources.list for instance)

My researchs brought me these proposals, are they equivalent or to be rejected :

• pkexec env DISPLAY=$DISPLAY XAUTHORITY=$XAUTHORITY gedit

• gedit admin:///path/to/document

• sudo -i gedit

• sudo -H gedit

Any other ?