umount2(2)

NAME

     umount, umount2 - unmount a file system

SYNOPSIS

     #include <sys/mount.h>

     int umount(const char *file);

     int umount2(const char *file, int mflag);

DESCRIPTION

     The umount()  function requests that  a  previously  mounted
     file system contained on a block special device or directory
     be unmounted.  The file argument is a pointer to  the  abso-
     lute  pathname  of  the  file  system to be unmounted. After
     unmounting the file system, the  directory  upon  which  the
     file  system was mounted reverts to its ordinary interpreta-
     tion.

     The umount2()  function is identical to umount(),  with  the
     additional  capability  of  unmounting  file systems even if
     there are open files active. The mflag argument must contain
     one of the following values:

     0     Perform  a  normal  unmount  that  is  equivalent   to
           umount().  The  umount2()  function   returns EBUSY if
           there are open files active within the file system  to
           be unmounted.

     MS_FORCE
           Unmount the file system, even if there are open  files
           active.  A  forced unmount may resort in loss of data,
           so it should be used only when a  regular  unmount  is
           unsuccessful.  The umount2() function  returns ENOTSUP
           if  the  specified  file  systems  does  not   support
           MS_FORCE.  Currently  only nfs- and ufs-type file sys-
           tems support MS_FORCE.

RETURN VALUES

     Upon successful completion, 0 is returned. Otherwise, -1  is
     returned and errno is set to indicate the error.

ERRORS

     The umount() and umount2() functions will fail if:

     EBUSY A file on file is busy.

     EFAULT
           The file pointed to  by  file  points  to  an  illegal
           address.

     EINVAL
           The file pointed to by file is not mounted.

     ENOENT
           The file pointed to by file does not exist.

     ELOOP Too many symbolic links were encountered in  translat-
           ing the path pointed to by file.

     ENAMETOOLONG
           The length of the file argument exceeds  PATH_MAX,  or
           the length of a  file component exceeds NAME_MAX while
           _POSIX_NO_TRUNC is in effect.

     ENOLINK
           The file pointed to by file is on a remote machine and
           the link to that machine is no longer active.

     ENOTBLK
           The file pointed to by file is  not  a  block  special
           device.

     EPERM The process's effective user ID is not superuser.

     EREMOTE
           The file pointed to by file is remote.

     The umount2() function will fail if:

     ENOTSUP
           The file pointed to by  file  does  not  support  this
           operation.

USAGE

     The umount() and umount2() functions may be invoked only  by
     the  superuser.  Because  it provides greater functionality,
     the umount2() function is preferred.

SEE ALSO

     mount(2)