Menu bar missing in KDE after updating
 

The menu bar - and pretty much everything else on my desktop - has disappeared after I let the system update itself.

Only the bar at the bottom is still there, and I can't start any applications, not even a terminal. No icons, no background, no anything (I got Firefox running by clicking on a link in the About KDE menu item in the task manager, which i started with ctrl-alt-del)

During the update the system just restarted, and afterwards it was like that.

How do I get it to work again?

Hi, please specify which distribution and KDE version you're using.
A first (hardcore) solution that comes to mind is to rename the .kde4 (notice the "." it means its a hidden file, its a part of the file name) folder and let KDE regenerate the configuration contained in there from scratch. This of course isn't acceptable if you've done some amount of KDE tweaking on your system.
Next is to check whether you have plasma-desktop running (task manager) if it isn't start it through krunner (alt+F2).
So you still have the task bar and the start menu? try starting an app by using krunner.

Unfortunately I have no idea what distribution and KDE version it is. I tried finding out, but couldn't see it anywhere.
I must stress that I am completely new to Linux (actually it's not even my own computer, it belongs to a friend that knows even less about it than I do).
But I can't find access to the files on the system anywhere. The task bar (as I understand the one at the bottom is called) doesn't have a start menu/button (like it has in Windows for instance).
On top of that alt+F2 does nothing. (I'm supposed to press it when on the desktop, right?)

What I have right now is a bar at the bottom with the 'show desktop' button on the left, some icons (volume, the clock, num lock and caps lock, a shutdown button etc.) on the right, and access to task manager and - through that - to firefox. I can't get anything else running.

It might be that there's just some really basic thing about Linux I don't know.

Right-click on the bottom panel and select New Panel. It will likely show up on the right side. Right-click on it and select Properties. Set the Orientation to Top. Right-click on the panel and select Add to Panel. Select Menu Bar and Add.

After that, you can add the other missing items.

Cheers, Lou

EDIT: Sorry. Disregard. This works for Gnome.

I'm already stuck at 'right-click on the bottom panel'. Nothing happens when I do this.

My mistake. Instructions are for Gnome.

To get the KDE version, just look at the "about" box you used to open firefox. The Distribution might be mentioned there too.
Alt+F2 should work anywhere and start up krunner, if it doesn't, that's very weird, since the task manager uses it.
Try right-clicking on the desktop, check that your widgets are "unlocked", click on the "cashew" (little foot-like symbol) in the panel, and from there you should be able to add widgets to the panel (the startmenu is a widget).
You can also add a new panel by right-clicking anywhere on the desktop and selecting "add panel".I personnaly call the taskbar (taskpanel) any panel that contains the task manager widget, it usually is on the bottom.
Since this happened after a (failed?) update; I'd start by trying to finish it and repair the damage using the package manager. But for us to be able to guide you, you'll have to give us the name of the distribution you're using.

[SOLVED] Menu bar missing in KDE after updating
 

More than 10 years later, the same problem still happens.

I'm using openSUSE and, in this case, you can right click anywhere on the desktop and then select [+ Add Panel] and then select [Default openSUSE Panel]. There's also another option [Default Panel] which appears on Debian too and possibly other distributions.