@Paul
uname -a
http://git.busybox.net/busybox/tree/coreutils/uname.c
#include "libbb.h"
/* After libbb.h, since it needs sys/types.h on some systems */
#include <sys/utsname.h>
Which are part of libc6 http://www.gnu.org/software/libc/manual/html_node/Platform-Type.html
"Some systems provide a mechanism to interrogate the kernel directly for this information. On systems without such a mechanism, the GNU C Library fills in this field based on the configuration name that was specified when building and installing the library."
These commands output parts of uname output:
cat /proc/version
sysctl -a | grep -e kernel.version -e kernel.ostype -e kernel.osrelease