This "polkit" stuff is all very good, and if that's what you want to use fine. But it's going to require a bit of setting up to use. I do not know how much configuring you want to do, or how "secure" you need to be for your purposes.

I will just say that in terms of "simplicity", if that's really what you want, my two thoughts would be:

• Use sudo and rely on what I quoted from the man page to ensure the user only gets prompted for password once every 15 minutes, if that works for you.

• Use setuid. It sounds like all your commands are apt updates? I would not make your Qt program itself setuid (unless you really know what you are doing). Rather, a tiny executable wrapper program supplied with your Qt app to just do apt update with setuid would suffice (installed with just chown root & chmod u+s). I would suggest this might be the simplest solution if you want to avoid any password prompting at all, as per your original question. Have you at least considered/do you know about setuid, even if you have good reason to reject it?

pkexec as i understand is: "A application used to interface with the polkit actions and authenticate an application to acquire root access." So that's a part of getting root access. https://stackoverflow.com/questions/47885043/proper-method-to-acquire-root-access-on-linux-for-qt-applications

Think of it as i calling sudo apt update multiple times in the program and doing things in the QT application in between.

I'm grateful for your answers.
Thanks.

sudo && pkexec ...

I would imagine that, since each segment separated by &&s (or whatever similar) is run its own separate sub-shell, the sudo's "lifetime" will only be its own sub-shell, and therefore assuming your intention was to run the later pkexec ... on the command-line under sudo (that was what you were intending, right?) it will in fact have "been & gone", leaving the pkexec ... running not as sudo after all...

To be clear: not trying to nit-pick on you, I too am not always 100% and like to learn, am just trying to produce a heads-up clarification for @fleppe if he tries yours and it doesn't work.

As I said earlier, I would expect

process.start("sudo " + pkexec_command)

to correctly run the pkexec as sudo.

However, unless OP has marked his sudo to require no password (as I do, on my own machine), this might prompt for sudo credentials each time for each pkexec, which he says he wishes to avoid? From man sudo I think this approach relies on:

Security policies may support credential caching to allow the user to run
sudo again for a period of time without requiring authentication. The
sudoers policy caches credentials for 15 minutes, unless overridden in
sudoers(5). By running sudo with the -v option, a user can update the
cached credentials without running a command.

If that is no good, one solution would be: Assuming you know what multiple pkexecs you wish to execute, send them all off to a text file as separate commands and run that file once via sudo.

If all you're suggesting to OP is to use sudo, that accepts the command as-is on the line. So what about something like:

process.start("sudo " + command)

(There are various ways of passing arguments separately/together, each have their advantages/disadvantages. To be clear I'm using the straightforward QString overload. There may be quoting issues, but yours will have those too.)