[Solved} Running in software rendering mode

[Captain Brillo]

Getting this message with Mint 19 Cinnamon in VirtualBox.

Running in software rendering mode

What does this mean, and how do I fix it?

[ClixTrix]

You will need to Install the VB Guest Additions. This method should work for 19 Cinnamon (as I'm already there).

1) With the guest machine started, go to the top menu on the machine window and click on Devices. From the drop-down list select "Insert Guest Additions CD Image ...". That will launch the installer window and select Run. It should bring up a Terminal Window and ask for password to proceed with install. You'll need to shutdown the machine after install completes.

2) From the Host VB Manager window, you'll need to select the machine and look in the Display Settings for "Enable 3D Acceleration".

3) Now start the machine.

Note, you might encounter a muddy background image after boot. I believe this is an old X11 problem that hasn't gotten much attention. If you toggle to another background after start, it does clear-up the image.

[Captain Brillo]

The thing is that it is the installation iso that first says

"running in software rendering mode"

All settings are as normal, there are 4 other VMs on this box without this problem.
But the same issue happens when trying to install Debian 9.

Is there something different about these 2 iso's?

[Captain Brillo]

The above issue is with Mint 19 (or Debian 9) Cinnamon.
Mate or XFCE are fine.

The VMs are set at 2 GB RAM / 128 MB display / 2-processors / 3D Acceleration / 100GB virtual disk (big HDD)
What else might point to the reason?

[jimallyn]

The above issue is with Mint 19 (or Debian 9) Cinnamon.
Mate or XFCE are fine.

The VMs are set at 2 GB RAM / 128 MB display / 2-processors / 3D Acceleration / 100GB virtual disk (big HDD)
What else might point to the reason?

Cinnamon requires 3D video acceleration. If you don't have it, or don't yet have it enabled in your VirtualBox installs by installing the Guest Additions, you will always get that message. ClixTrix gave you the solution.

[Captain Brillo]

As I said, 3D Acceleration IS on.
Turns out that the VB guest stuff was corrupted and I had to reinstall VB.
Working now.

Thanks all.

[Pierre]

YEP - - I've had to re-install the VB Guest Additions, on more than one occasion.

sometimes, even the VB software update, makes things go pear-shaped.