/usr/src : Source code

For systems based on glibc, there are no specific guidelines for this directory. For systems based on Linux libc revisions prior to glibc, the following guidelines and rationale apply:

The only source code that should be placed in a specific location is the Linux kernel source code. It is located in /usr/src/linux.

If a C or C++ compiler is installed, but the complete Linux kernel source code is not installed, then the include files from the kernel source code must be located in these directories:

    /usr/src/linux/include/asm-<arch>
    /usr/src/linux/include/linux

<arch> is the name of the system architecture.

	Note
	/usr/src/linux may be a symbolic link to a kernel source code tree.

It is important that the kernel include files be located in /usr/src/linux and not in /usr/include so there are no problems when system administrators upgrade their kernel version for the first time.