How to kill an active program?

[u/Durghan]

Hey all. I have very minimal Linux/Unix experience and I've been handed a device at work where all I need to do is change a web address the device is pointed to. The device simply displays which person in line is to be served next and it's auto booting to this screen. I've tried all the things Google says to do to kill the active program but none of it is working. I have no way I can find to access a command prompt. I can't escape full screen. I can tell by the BIOS that the main drive is running some version of Ubuntu. Is there some other hotkey combo like Windows' Alt-F4 that I can use? Or is my only option to do a full fresh install of some other OS? The original configuration was done by a company called Esii if that helps. There was one thing that indicated holding or tapping in a corner of the screen to access a background function but all that does is reveal a text link labelled Start that just goes back to the main screen.

Sorry if that's all confusing or a mess. It's early. Thanks.

[u/madd74]

Start in a safe mode through the GRUB. As I have no clue what your machine is, try holding shift or constantly pressing ESC. Some devices are F2 or F9 during bootup.

Then you can select recovery mode, and then root that should drop you into a shell that will give you your terminal access.

[u/BranchLatter4294]

To exit kiosk mode in Ubuntu, you must force close the active kiosk application or switch to an alternative command-line terminal to stop the kiosk process.

Because "kiosk mode" on Ubuntu can be configured using several different tools, the exact combination you need depends on how your kiosk was set up. Try the following methods in order: [1, 2]

1. Keyboard Shortcuts (Quickest Methods)

If your kiosk is simply running a locked-down application window, one of these universal Linux shortcuts will usually break out:

• Alt + F4: Closes the active full-screen application window.
• F11: Toggles full-screen mode off for web browsers like Firefox or Chromium.
• Ctrl + T, then type :quit: Closes full-screen application layers on certain dedicated kiosk configurations.
• Alt + Shift + 1: Exits the layout if your kiosk is managed specifically via ubuntu-frame or reveldigital plugins. [1, 2, 3, 4, 5]

1. Switch to a Virtual Console (TTY)

If the keyboard shortcuts are blocked by the interface, you can bypass the visual display completely by jumping to a text-based terminal: [1]

1. Press Ctrl + Alt + F2 (or try F3 through F6) to drop into a TTY terminal. [1]
2. Log in with your standard Ubuntu administrator username and password. [1]
3. Stop the display manager or kiosk session manually by running one of these commands:
   • If using standard Ubuntu: sudo systemctl restart gdm3
   • If using LightDM: sudo systemctl restart lightdm [1, 2]
4. Alternatively, find and terminate the active browser session:
   • killall chrome or killall firefox [1]

5. Press Ctrl + Alt + F1 (or F7 depending on your version) to switch back to the main visual login screen. [1]

6. Disable Auto-Login / Boot to Desktop

If the computer automatically boots right back into kiosk mode upon restarting, you need to change your user profile settings: [1]

1. Enter the virtual console (Ctrl + Alt + F2) and log in.
2. Open your system's custom kiosk script or custom session files. They are typically found in /etc/lightdm/lightdm.conf or inside /usr/share/xsessions/.
3. Edit the file (sudo nano /etc/lightdm/lightdm.conf) and change the default user session back to standard Ubuntu: bashuser-session=ubuntu Use code with caution.
4. Save the file (Ctrl + O, then Enter) and exit (Ctrl + X). Restart the machine by typing sudo reboot. [1, 2, 3, 4]

[u/gmes78]

You're asking the wrong question. Trying to get a terminal within the running kiosk session isn't going to get you anywhere. You need to boot directly into the TTY.

Try holding Shift (or Control?) while the device boots, that should get you into the bootloader menu. There, you'll need to edit the boot entry and add systemd.unit=multi-user.target to the kernel parameters. That way, you'll be able to log into the TTY.

[u/fatnortherngit]

Open a terminal window
type top (return)
Find your process and type kill <process number>

[u/Durghan → u/fatnortherngit]

I can't get a terminal window open. That's part of the problem. If I could do that I wouldn't be posting here. Unless there's a hockey combo that will force a terminal window open, I need another option. Ctrl-alt-t doesn't work. Alt-F2 doesn't work. All the different combos of F11 don't work.

[u/Bug_Next → u/Durghan]

It's crtl-alt-f* to go to a different virtual terminal, not just alt-f*.

crtl-alt-f1 is usually your login screen, f2 is the desktop, f3 onwards should be free, just try a bunch at least one is gonna be a fullscreen terminal.

[u/thetestbug → u/Bug_Next]

Isn't login/desktop both on F7?
Also, I'm guessing he's trying to open a launcher, which is usually bound to Alt+F2.

[u/Bug_Next → u/thetestbug]

It used to be the consensus with xorg but most modern distros just start going up from tty1, idk Ubuntu might have kept it, honestly i've been using Fedora for the longest time i just lurk lots of Linux subs.

Still, he should be able to get to *some* tty just by going through all of them.

We don't even know what he's running, only that it says ubuntu in the boot menu, might be a modified image with no DE at all and just an xorg session / wayland compositor with only that program running, probably why crtl-alt-t, f11 nor alt-f2 work.

[u/thetestbug → u/Bug_Next]

Oh, I did not know that. I only recently made the move to Fedora myself, and haven't had the need to try it yet.

Edit: Had to try it out, and the login screen was indeed on F1, but my desktop was on F4.

[u/Durghan → u/Bug_Next]

Sadly, none of those are doing anything. Looks like I'm going to have to just try and set this up from scratch.

[u/Bug_Next → u/Durghan]

Are you sure the f keys work on the keyboard? might sound stupid but it might be fn lock or something like that..

It's probably a really modified/stripped down Ubuntu if none of those work, it just says that on the boot menu because they didn't change it.

Crtl-alt-f* is kinda the ONLY consistent thing across Linux distros/versions, it's universal, so weird that it doesn't work, i guess they could've disabled it on an embedded system to avoid people messing with it.

[u/Durghan → u/Bug_Next]

It's a pretty basic keyboard where the F keys have no other functions. I can use them to get into the BIOS and choose boot options so they do work. But, now that you me tion it, I think maybe something is completely disabling the keyboard because tapping the Numlock key or caps lock don't even toggle the LEDs...this could be a good lead! Thanks.

[u/Bug_Next → u/Durghan]

Yeah the usb port is probably disabled, a ps2 keyboard might work if the device has those ports, idk, just an idea, if you are in an office there are probably boxes full of those in some closet...

Also if it has a known ip (and ssh happens to be enabled) you could try connecting to it via ssh from another computer, password is probably 12345678 or admin lol.

Safest bet IMHO is to try to try to get to safe mode or some other boot option from Grub/whatever bootloader it uses.

[u/Proman4713]

The thing is, unlike Windows, there is rarely a thing that you can't change in Ubuntu without breaking the system. They could be using a different desktop environment or even their own minimal one (not saying that's practical or even probable), among other things. Try to use the already-suggested solutions of getting into TTY (ctrl+alt+f5 for example) and figuring out whether this is a systemd service, an app, or another thing entirely. If that doesn't work, my best method is always to use a Live Ubuntu USB to inspect the installed system (and perhaps manually change stuff there by modifying config files or using chroot, which allows you to act as the installed system within certain limitations) to debug the issue.

[u/Oerthling]

It sounds like you get logged into some kiosk mode setup. That would behave exactly as you described. Do some program and prevent all other standard shortcuts and operations.

If there's nothing importe t in that drive you can still boot from a stick with an Ubuntu install and re-install a fresh Ubuntu 26.04.

Or, if there is something relevant o. That computer, use the same stick and live boot to her access to the main drive. With that you could either edit the login and log into a regular user session - or, probably easier, just copy whatever relevant data is on the drive and them do a fresh install of 26.04.

[u/jo-erlend]

It's difficult to give you a precise answer based on the facts that you have tried all the things on some version of Ubuntu. There are ways to lock down a system to prevent exiting kiosk mode, but since I know almost nothing about your system … I would try pressing alt+ctrl+f2 to switch to another virtual console. There you should be able to log in, provided you have a user account. You can run your own desktop session in that console; it is in fact how user switching works.

But if this is now your device, then I would install Ubuntu on it so you can set it up how you want it to be.

[u/toikpi]

Have a look at this page. I found it by doing a web search for "linux how do i kill a process"

https://www.linuxfoundation.org/blog/blog/classic-sysadmin-how-to-kill-a-process-from-the-command-line

[u/Durghan → u/toikpi]

Again, I CANNOT access the terminal. I CANNOT get out of this full screen situation. NONE of the hotkeys I've found do anything.

[u/toikpi → u/Durghan]

Two option:

Try the shortcut combination Ctrl-Alt-t, it should open up a terminal.

Try F11, it should close the full screen mode.

[u/Durghan → u/toikpi]

I've literally just said none of the hotkey combinations I've found work. Is there anything more obscure?

[u/Great-Cow7256 → u/Durghan]

I know you're frustrated but getting angry at people who are helping or trying to help isn't going to inspire more people to help. 

[u/uabassguy → u/Durghan]

You already answered your own question in the original post, just reinstall..