By Dominic Duval, Red Hat Certfied Engineer
As a way to save a few valuable pennies on newer PCs, manufacturers are increasingly getting rid of the good old PS/2 keyboard and mouse interfaces. As a result, some recent systems only ship with USB ports to which we need to connect a USB keyboard and mouse.
USB is all well and good, but what if the driver for your USB controller is not loaded? In practice, this is not a problem, as Red Hat loads the ehci- hcd and uhci-hcd drivers automatically at boot time.
There are situations, namely in emergency mode, where the USB drivers won’t be available. So you won’t even be able to enter a command. This is due to the fact that in emergency mode all drivers need to be provided in the initrd file under /boot, and USB is not there by default. The trick is to add those drivers, so that they will be available earlier. The ‘mkinitrd’ command can do precisely that with the ‘–with’ argument (this only works under RHEL4):
mkinitrd –with=ehci-hcd –with=uhci-hcd /boot/newinitrd-`uname -r`.img `uname -r`
Add a new entry in your grub.conf file (always do backups!) that points to this new initrd image, and you’re done! Your USB keyboard now works in emergency mode.