The Linux kernel defines the following unmount() flags (in include/linux/fs.h):
#define MNT_FORCE 0x00000001 /* Attempt to forcibily umount */
#define MNT_DETACH 0x00000002 /* Just detach from the tree */
#define MNT_EXPIRE 0x00000004 /* Mark for expiry */
Glibc exposes the MNT_FORCE flag in <sys/moun.t>, but not the other two flags.
The other two flags are nevertherless useful to userland, and should be defined
in glibc. MNT_DETACH is available since Linux 2.4.11. MNT_EXPIRE is available
since Linux 2.6.11.
*** This bug has been marked as a duplicate of 10092 ***