I don't know of a way to disable video but there's a few ways to disable USB.
- Edit grub.conf, append 'nousb', and reboot. (via)
- Blacklist usb kernel modules using instructions on the CentOS wiki. They're written for usb-storage you'd need to modify them to blacklist things like a USB keyboard.
If the server is already running, you can try removing the usb modules while its running. You could possibly disable the usual virtual terminals on alt+f1 and so on, by commenting out their lines in /etc/inittab and
kill -HUP 1 so there's no 'obvious' way to log in but there's always ssh to worry about then.
With that said, like Gilles said, that's really not going to protect your system. Anyone can take the drives out of your server and copy the data from it assuming they're not encrypted.
If your goal is to stop people from messing with it, not stealing the data on the drives there's a few options since you mention you have a Dell R310. These might not be applicable now since it sounds like the server is already deployed, but might be helpful in the future:
- Put a password on the BIOS
- Use the front cover bezel to disable access to the hard drives, DVD-ROM, front USB ports, and front video port. I think there's a BIOS setting to disable the rear video and usb ports, but can't find it in their docs. The logic is the only way to service the machine is through the front ports which require a key that only you have. Worst case you could render the rear ports physically inoperable.
- The R310 offers intrusion alert.
- The R310 can boot from an internal usb key.
- The R310 lists several more things in its manual about physical security that might be applicable.
With Dell's OpenManage I believe you can change some BIOS settings from the operating system assuming you install their tools for Linux so you might be able to do some of these now.