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)