How to fix Raspi camera 'failed to open vchiq instance'

Problem:

You are trying to access the Raspberry Pi camera using raspistill or raspivid. Although you already enabled the camera interface using raspi-config, you see this error message:

* failed to open vchiq instance

Solution

Your user does not have the permissions to access the camera interface. As a quick fix, you can run raspistill or raspivid as root using sudo, or add your user to the video group to acquire the required permissions:

sudo usermod -a -G video $USER

sudo usermod -a -G video $USER

After doing this, log out and log back in again for the changes to take effect - or close your SSH session and connect again. If in doubt, try to reboot.