Boot-Time Driver Loading — A Choreographed Sequence
A short look at the early-boot driver sequence — start types, load groups, and the safety net for missing drivers.
Start Types Determine Order
Drivers register a start type — boot, system, automatic, manual. Boot drivers load before the rest of the operating system has even initialised; they include the driver for the disk that holds the operating system itself. System drivers load next; automatic drivers follow once the operating system is up.
The order is not arbitrary. A storage driver must be present before the operating system can read its own files. A graphics driver only loads later because the early console is enough until then.
Load Groups and Dependencies
Within each start type, drivers belong to load groups. The bus drivers load before the device drivers that sit on top of those buses. Within a load group, individual dependencies can be expressed so that a driver waits for another to finish.
This is how the operating system avoids loading a network adapter driver before the chipset driver has exposed the bus the adapter sits on.
When a Boot Driver Is Missing
If a boot driver is missing or fails to load, the operating system has a recovery story — it boots into a safe environment with only essential drivers loaded, where you can repair the install and restore the missing driver.
For automatic drivers that fail, the operating system continues booting and reports the failure once you log in. The most common cause is a corrupt driver file, which is easy to address by reinstalling the package.
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