Driver Update Disk Handling

anaconda-dracut takes advantage of dracut's hooks in order to load driver
modules before the rest of the installer is executed.


cmdline hook
    parse-anaconda-dd.sh
    parses the inst.dd/dd arguments for URIs and saves all of them into $dd_args
    and calls set_neednet if network is needed to retrieve a driver rpm
    The files will be downloaded when the network device online hook is executed.

initqueue/online
    fetch-driver-net.sh
    If URLs are passed to inst.dd they are all downloaded into /tmp/DD-net/

pre-trigger hook
    driver-updates.sh
    Looks for devices labeled OEMDRV and starts the systemd service for the UI
    Also saves the initial state of the module list and uses udev to trigger
    loading of existing modules.

pre-pivot hook
    driver-updates-net.sh
    Check for network downloaded driver rpms and start the systemd service to
    load the drivers.

    anaconda-depmod.sh
    If any drivers were installed or downloaded run depmod on the $NEWROOT


Systemd Services
    driver-updates@.service and driver-updates-net@.service
    These services launch the driver update UI (/bin/driver-updates). The -net
    version passes the path to the rpm's that have been downloaded from the
    network. They handle connecting the tty so that the user can select drivers
    if inst.dd has been passed on the cmdline.


driver-updates
    This searches disks labeled OEMDRV for driver update repositories and
    optionally lets the user pick individual drivers. It will also search
    unlabeled devices if they are passed on the kernel cmdline with
    inst.dd=/dev/sdb2

    Pass it the path to a directory of rpms (eg. downloaded from the
    network) and it will install them before checking for additional OEMDRV
    labeled devices.

    Pass inst.dd with no parameters and it will prompt the user for specific
    drivers to load using a simple text user interface.