/kernel and 8.3 file names

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 :)

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About me

Johannes Passing, M.Sc., living in Berlin, Germany.

Besides his consulting work, Johannes mainly focusses on Win32, COM, and NT kernel mode development, along with Java and .Net. He also is the author of cfix, a C/C++ unit testing framework for Win32 and NT kernel mode, Visual Assert, a Visual Studio Unit Testing-AddIn, and NTrace, a dynamic function boundary tracing toolkit for Windows NT/x86 kernel/user mode code.

Contact Johannes: jpassing (at) acm org

Johannes' GPG fingerprint is BBB1 1769 B82D CD07 D90A 57E8 9FE1 D441 F7A0 1BB1.

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