MOUNT(2) System Calls MOUNT(2)

NAME

mount - mount a file system

SYNOPSIS

#include <sys/types.h>
#include <sys/mount.h>
#include <sys/mntent.h>

int mount(const char *spec, const char *dir, int mflag,
char *fstype, char *dataptr,int datalen, char *optptr,
int optlen);

DESCRIPTION

The mount() function requests that a removable file system contained
on the block special file identified by spec be mounted on the
directory identified by dir. The spec and dir arguments are pointers
to path names.


After a successful call to mount(), all references to the file dir
refer to the root directory on the mounted file system. The mounted
file system is inserted into the kernel list of all mounted file
systems. This list can be examined through the mounted file system
table (see mnttab(5)).


The fstype argument is the file system type name. Standard file
system names are defined with the prefix MNTTYPE_ in <sys/mntent.h>.
If neither MS_DATA nor MS_OPTIONSTR is set in mflag, then fstype is
ignored and the type of the root file system is assumed.


The dataptr argument is 0 if no file system-specific data is to be
passed; otherwise it points to an area of size datalen that contains
the file system-specific data for this mount and the MS_DATA flag
should be set.


If the MS_OPTIONSTR flag is set, then optptr points to a buffer
containing the list of options to be used for this mount. The optlen
argument specifies the length of the buffer. On completion of the
mount() call, the options in effect for the mounted file system are
returned in this buffer. If MS_OPTIONSTR is not specified, then the
options for this mount will not appear in the mounted file systems
table.


If the caller does not have all privileges available in the current
zone, the nosuid option is automatically set on the mount point. The
restrict option is automatically added for autofs mounts.


If the caller is not in the global zone, the nodevices option is
automatically set.


The mflag argument is constructed by a bitwise-inclusive-OR of flags
from the following list, defined in <sys/mount.h>.

MS_DATA
The dataptr and datalen arguments describe a block of
file system-specific binary data at address dataptr
of length datalen. This is interpreted by file
system-specific code within the operating system and
its format depends on the file system type. If a
particular file system type does not require this
data, dataptr and datalen should both be 0.


MS_GLOBAL
Mount a file system globally if the system is
configured and booted as part of a cluster (see
clinfo(8)).


MS_NOSUID
Prevent programs that are marked set-user-ID or set-
group-ID from executing (see chmod(1)). It also
causes open(2) to return ENXIO when attempting to
open block or character special files.


MS_OPTIONSTR
The optptr and optlen arguments describe a character
buffer at address optptr of size optlen. When calling
mount(), the character buffer should contain a null-
terminated string of options to be passed to the file
system-specific code within the operating system. On
a successful return, the file system-specific code
will return the list of options recognized.
Unrecognized options are ignored. The format of the
string is a list of option names separated by commas.
Options that have values (rather than binary options
such as suid or nosuid), are separated by "=" such as
dev=2c4046c. Standard option names are defined in
<sys/mntent.h>. Only strings defined in the "C"
locale are supported. The maximum length option
string that can be passed to or returned from a
mount() call is defined by the MAX_MNTOPT_STR
constant. The buffer should be long enough to contain
more options than were passed in, as the state of any
default options that were not passed in the input
option string may also be returned in the recognized
options list that is returned.


MS_OVERLAY
Allow the file system to be mounted over an existing
file system mounted on dir, making the underlying
file system inaccessible. If a mount is attempted on
a pre-existing mount point without setting this flag,
the mount will fail.


MS_RDONLY
Mount the file system for reading only. This flag
should also be specified for file systems that are
incapable of writing (for example, CDROM). Without
this flag, writing is permitted according to
individual file accessibility.


MS_REMOUNT
Remount a read-only file system as read-write.

RETURN VALUES

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

ERRORS

The mount() function 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
The dir argument is currently mounted on, is
someone's current working directory, or is otherwise
busy; or the device associated with spec is currently
mounted.


EFAULT
The spec, dir, fstype, dataptr, or optptr argument
points outside the allocated address space of the
process.


EINVAL
The super block has an invalid magic number, the
fstype is invalid, or dir is not an absolute path.


ELOOP
Too many symbolic links were encountered in
translating spec or dir.


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


ENOENT
None of the named files exists or is a null pathname.


ENOLINK
The path argument points to a remote machine and the
link to that machine is no longer active.


ENOSPC
The file system state in the super-block is not
FsOKAY and mflag requests write permission.


ENOTBLK
The spec argument is not a block special device.


ENOTDIR
The dir argument is not a directory, or a component
of a path prefix is not a directory.


ENOTSUP
A global mount is attempted (the MS_GLOBAL flag is
set in mflag) on a machine which is not booted as a
cluster; a local mount is attempted and dir is within
a globally mounted file system; or a remount was
attempted on a file system that does not support
remounting.


ENXIO
The device associated with spec does not exist.


EOVERFLOW
The length of the option string to be returned in the
optptr argument exceeds the size of the buffer
specified by optlen.


EPERM
The {PRIV_SYS_MOUNT} privilege is not asserted in the
effective set of the calling process.


EREMOTE
The spec argument is remote and cannot be mounted.


EROFS
The spec argument is write protected and mflag
requests write permission.

USAGE

The mount() function can be invoked only by processes with
appropriate privileges.

SEE ALSO

umount(2), mnttab(5), mount(8)

NOTES

MS_OPTIONSTR-type option strings should be used.


Some flag bits set file system options that can also be passed in an
option string. Options are first set from the option string with the
last setting of an option in the string determining the value to be
set by the option string. Any options controlled by flags are then
applied, overriding any value set by the option string.

February 26, 2004 MOUNT(2)