/kernel and 8.3 file names

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Although the Windows file systems have supported filenames with more than 8 chanracters for years, it has still remained good practice (at least for native development) to name modules in 8.3 format. While modules not adhering to this practice normally work well, there is at least one situation where giving a module a long file name does make a real difference: the file name of the kernel.

The default kernel file name is ntoskrnl.exe. Using the /kernel boot parameter, this default can be overridden and an arbitrary file can be specified to be loaded as kernel – this is especially useful when you routinely switch between different kernels, such as the free and checked build.

If, however, you try to give your alternate kernel a non-8.3 name, you will be saluted with the following screen on next boot:

boot screen

Quite obviously, ntldr is not capable of loading a kernel from a non-8.3 file :)

Any opinions expressed on this blog are Johannes' own. Refer to the respective vendor’s product documentation for authoritative information.
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