Where has gksu gone?

[deadflowr]

Ok thanks, but where do I have to type your code?

In the terminal
It'll run like any other command.
then run your root command.

xhost si:localuser:root
then press enter
then try
synaptic-pkexec or some other root gui app

the xhost command switches you to use root apps, but only for the current desktop session in use.
To set as persistent you can add the line to a new Startup Application entry.
That way it'll run everytime you log in.

[mc4man]

For example, if I wanted to start synaptic, I entered the following command in /usr/share/applications/synaptic.desktop: Exec=gksu synaptic
That way, by clicking the synaptic icon it was started as root (which is needed, because otherwise you won't be able to install additional software)

Any thougths?

By default synaptic has been using /usr/bin/synaptic-pkexec & corresponding line in it's .desktop for at least the last 6 years. So no sure why you previously saw fit to change that.
(- unless you were editing synaptic-kde.desktop instead of synaptic.desktop

Is this a fresh install of 18.04 or are you re-using your home folder, i.e you did an upgrade from earlier Ubuntu release or you installed over the previous install's partition without formatting or whatever..

[lieven-debels]

I did an update of 17.10 to 18.04 by changing every instance of 'artful' to 'bionic' in /etc/apt/sources.list.
Then ran apt-get update, apt-get upgrade and apt-get dist-upgrade.

Still the suggestion from deadflowr (in post #11), doesn't seem to solve the problem.

[deadflowr]

I did an update of 17.10 to 18.04 by changing every instance of 'artful' to 'bionic' in /etc/apt/sources.list.
Then ran apt-get update, apt-get upgrade and apt-get dist-upgrade.

How recently?
Wonder if there is leftover junk causing issues.

[rbmorse]

I upgraded my 17.10 to 18.04 (beta2) on Xorg using the method here: https://linuxconfig.org/how-to-upgra...-bionic-beaver (Ubuntu method).

To run synaptic (it's one of those cold, dead hands apps for me) I open a terminal and run:

synaptic-pkexec

That gives me a password dialog followed by Synaptic with root privileges.

[Irihapeti]

To get the pkexec password dialogue, you need to have one of the polkit / policykit agents installed. e.g. lxpolkit, mate-polkit, policykit-1-gnome.

One of those would be installed as a matter of course if you're using a full install of a flavour. Usually, it's only an issue if you have a custom install based on a minimal system.

[lieven-debels]

I do have a custom install, started from the ubuntu 17.10 mini.iso but policykit-1-gnome is installed, so I don't know why it still doesn't work.
Can someone please look at the screenshot of the terminal window I posted yesterday. Does that give some possible clue what's going wrong?
Or can I troubleshoot this in another way?

[deadflowr]

Try a quick pkexec test

pkexec test

does it open the popup dialog password box?
Or is the password field inside the terminal?

Here's a Debian bug report with similar output of the screenie posted
https://bugs.debian.org/cgi-bin/bugr...cgi?bug=841878
(btw, post the output directly into a post rather then pictures as images can only go so far)

[lieven-debels]

Finally made some progress: First (or after a reboot) I have to run from a terminal:

/usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1

Then

pkexec synaptic

works as expected. However in /usr/share/applications/synaptic.desktop there is:

Exec=synaptic-pkexec

which does NOT work as expected.
So basically now I need to know how to make this change permanently, and secondly, synaptic.desktop seems to use the wrong syntax (but it doesn't matter, because if i change synaptic-pkexec to pkexec synaptic, synaptic is still started without administrative privileges). It only seems to work if I issue the command pkexec synaptic directly. I was hoping that by typing just 'synaptic' the synaptic.desktop file would translate this to pkexec synaptic, but it doesn't.

[deadflowr]

The syntax is correct.
Perhaps, try a quick reinstall of synaptic.
Maybe a reinstall will do something to clean up any residual problems it has for you.

sudo apt install --reinstall synaptic