/usr/share/doc/kernel-doc-<version>/Documentation/filesystems/proc.txt — Contains assorted, but limited, information about all aspects of the /proc/ directory.

/usr/share/doc/kernel-doc-<version>/Documentation/sysrq.txt — An overview of System Request Key options.

/usr/share/doc/kernel-doc-<version>/Documentation/sysctl/ — A directory containing a variety of sysctl tips, including modifying values that concern the kernel (kernel.txt), accessing file systems (fs.txt), and virtual memory use (vm.txt).

/usr/share/doc/kernel-doc-<version>/Documentation/networking/ip-sysctl.txt — A detailed overview of IP networking options.