virtualbox.org

Running VBox on Win7 x64. CentOS5 32 bit guest running fine with GA, until reboot. On reboot, guest screen size dropped to default, and other GA integrations stopped working. (It prompts for mouse capture)

Possibly relevant is that an rsync used up most of available disk space just before the reboot, but no errors were reported.

What is the best GA reinstall procedure under these circumstances?

The manual indicates a service named VBoxService should be running.
I looked at the background service list under GNOME.

VBoxService is not listed
The following are checked, with the indicated message under status:
vboxadd: The VirtualBox Additions are not currently running
vboxadd-service: Checking for VBoxService ...not running.
vboxadd-x11: (nothing shown)

Where can I look to find the reason the VBoxService will not start/is not listed?
Can I use chkconfig to get it going? If so, which levels does it normally run in?

You probably got a kernel update in the VM and without DKMS, you have to rebuild the kernel modules. Reinstall the GA and see if it works again.

@sasquatch

You nailed it. The yum log shows it updated the kernel on the 31st. But I didn't reboot until today. I reinstalled the additions and all is back to normal. (I also disabled automatic updates )

Keep automatic updates on, install DKMS instead. That will ensure that kernel packages are rebuild for newly installed kernels.