- do early boot logic (putting udev into initramfs, handle pivot-root,
etc.)
- lots of other stuff...
-- actually use the BUS= value to determine where the LABEL rule should look
- (right now it's ignored, and we only look in the current sysfs directory.)
- This is needed, for example, to look at the usb device's serial number of a
- usb-storage device, instead of the scsi device's sysfs directory for the
- serial number.