UMOUNT(2) System Calls UMOUNT(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 absolute 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 interpretation.


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 can result 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.
Only file systems of type nfs, ufs, pcfs, and zfs 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:

EACCES
The permission bits of the mount point do not permit
read/write access or search permission is denied on a
component of the path prefix.

The calling process is not the owner of the
mountpoint.

The mountpoint is not a regular file or a directory
and the caller does not have all privileges available
in a its zone.

The special device device does not permit read access
in the case of read-only mounts or read-write access
in the case of read/write mounts.


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.


ELOOP
Too many symbolic links were encountered in
translating 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.


ENOENT
The file pointed to by file does not exist or is not
an absolute path.


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and the link to that machine is no longer active.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 {PRIV_SYS_MOUNT} privilege is not asserted in the
effective set of the calling process.


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 can be invoked only by a process
that has the {PRIV_SYS_MOUNT} privilege asserted in its effective
set.


Because it provides greater functionality, the umount2() function is
preferred.

SEE ALSO

mount(2), privileges(7)

August 4, 2008 UMOUNT(2)