Why does CTRL not work in VirtualBox VMs?

Question

I have recently noticed that for some reason when pressing CTRL in a VM in VirtualBox it doesn't get through... So I can't easily copy and paste etc, it just doesn't get through, the VM doesn't think that I've pressed anything when I press CTRL or at least it doesn't do anything, why is this? It doesn't seem to matter what I run as guest, and it didn't happen before with these same VMs so it's not that they all just don't like it, the problem probably is with VirtualBox. I have tried running Ubuntu GNOME 15.10, Ubuntu 16.04, and Ubuntu GNOME 16.04.

Information Update:

Neither the left, nor the right CTRL keys actually do anything, they don't even seem to interact with Virtual Box because pressing the right one should change something in it.

I have tried installing the Guest Additions CD in my VMs, but it makes no difference to my problem.

---

OS Information:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 15.10
Release:    15.10
Codename:   wily
Flavour: GNOME
GNOME Version: 3.18

Package Information:

Version: 5.0.14 r105127

Solution

I have figured out the problem!

The problem was that for some reason when one has the Show location of pointer option enabled in the gnome-tweak-tool, as this is assigned to CTRL, for some reason this prevents programs from capturing this key. So disabling that option in the gnome-tweak-tool fixes the issue.

Comments

[Sergiy Kolodyazhnyy]

VB uses left ctrl for controlling guest, right ctrl for host. That way you can use ctrl left for your guest os, and right for controlling vbox window

[Admin]

@Serg: Well, neither of them seem to do anything in VB/VM...

[Sergiy Kolodyazhnyy]

May be a version bug. I'm on 14.04, works alright here:)

[Javier Rivera]

Could it be a gnome thing?. Maybe the CTRL key is assigned by it to some function.

[Dan Dascalescu]

Already asked on SuperUser: Ctrl key doesn't work in Virtual Box, Linux host

[Admin]

Any keyboard shortcut with "CTRL" in it isn't going to do me that much good... :P

[Patrick Schaefer]

I was thinking your VM might be stuck using the ctrl key for host tasks and that is why ctrl isn't working within the VM. Using right ctrl + D executes on the host, not the VM in my understanding (specifically the right one, not left)

[Admin]

Ok, anyway, I have tried install Guest Additions, but it still doesn't work...

[towi]

amazing. how did you figure that out?

[user281609]

@towi: Because it was the only recent change I had made to the settings in terms of the keyboard and mouse in any way. So I put two and two together and gave reverting the setting a choice and thankfully it worked!

[apos]

Worked for me in Ubuntu 17.10 (Gnome, Xorg)

[user281609]

@apos: Yes, I seem to remember hearing about the fix for this bug being released.