I just upgraded my Debian5 workstation to 2.6.31. While doing so I stumbled over this: cc -m32 -Wall -Wmissing-declarations -Wmissing-prototypes -O3 -I../../include -I../../arch/x86/include -U_FORTIFY_SOURCE lguest.c -o lguest lguest.c:21:25: error: sys/eventfd.h: No such file or directory lguest.c: In function ‘create_thread’: lguest.c:1021: warning: implicit declaration of function ‘eventfd’