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    The following form allows you to view linux man pages.

    Command:

    umount2

    
    
    

    SYNOPSIS

           #include <sys/mount.h>
    
           int umount(const char *target);
    
           int umount2(const char *target, int flags);
    
    
    

    DESCRIPTION

           umount()  and umount2() remove the attachment of the (topmost) filesys-
           tem mounted on target.
    
           Appropriate privilege (Linux: the CAP_SYS_ADMIN capability) is required
           to unmount filesystems.
    
           Linux  2.1.116  added  the umount2() system call, which, like umount(),
           unmounts a target, but allows additional flags controlling the behavior
           of the operation:
    
           MNT_FORCE (since Linux 2.1.116)
                  Force  unmount  even  if busy.  This can cause data loss.  (Only
                  for NFS mounts.)
    
           MNT_DETACH (since Linux 2.4.11)
                  Perform a lazy unmount: make the mount point unavailable for new
                  accesses,  and actually perform the unmount when the mount point
                  ceases to be busy.
    
           MNT_EXPIRE (since Linux 2.6.8)
                  Mark the mount point as expired.  If a mount point is  not  cur-
                  rently  in use, then an initial call to umount2() with this flag
                  fails with the error  EAGAIN,  but  marks  the  mount  point  as
                  expired.   The  mount  point remains expired as long as it isn't
                  accessed by any process.  A  second  umount2()  call  specifying
                  MNT_EXPIRE unmounts an expired mount point.  This flag cannot be
                  specified with either MNT_FORCE or MNT_DETACH.
    
           UMOUNT_NOFOLLOW (since Linux 2.6.34)
                  Don't dereference target if it is a symbolic  link.   This  flag
                  allows  security problems to be avoided in set-user-ID-root pro-
                  grams that allow unprivileged users to unmount filesystems.
    
    
    

    RETURN VALUE

           On success, zero is returned.  On error, -1 is returned, and  errno  is
           set appropriately.
    
    
    

    ERRORS

           The  error  values  given below result from filesystem type independent
           errors.  Each filesystem type may have its own special errors  and  its
           own special behavior.  See the Linux kernel source code for details.
    
           EAGAIN A call to umount2() specifying MNT_EXPIRE successfully marked an
                  unbusy filesystem as expired.
                  A pathname was longer than MAXPATHLEN.
    
           ENOENT A pathname was empty or had a nonexistent component.
    
           ENOMEM The  kernel  could not allocate a free page to copy filenames or
                  data into.
    
           EPERM  The caller does not have the required privileges.
    
    
    

    VERSIONS

           MNT_DETACH and MNT_EXPIRE are available in glibc since version 2.11.
    
    
    

    CONFORMING TO

           These functions are Linux-specific and should not be used  in  programs
           intended to be portable.
    
    
    

    NOTES

           The  original  umount() function was called as umount(device) and would
           return ENOTBLK when called with something other than  a  block  device.
           In  Linux  0.98p4  a  call  umount(dir)  was added, in order to support
           anonymous devices.  In Linux 2.3.99-pre7 the  call  umount(device)  was
           removed,  leaving only umount(dir) (since now devices can be mounted in
           more than one place, so specifying the device does not suffice).
    
    
    

    SEE ALSO

           mount(2), path_resolution(7), mount(8), umount(8)
    
    
    

    Linux 2014-02-26 UMOUNT(2)

    
    
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