mount(2) System Calls mount(2)NAMEmount - 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 sys‐
tems. This list can be examined through the mounted file system table
(see mnttab(4)).
The fstype argument is the file system type name. Standard file system
names are defined with the prefix MNTTYPE_ in <sys/mntent.h>. If nei‐
ther 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 con‐
taining the list of options to be used for this mount. The optlen argu‐
ment 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 auto‐
matically 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-spe‐
cific 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 config‐
ured and booted as part of a cluster (see clinfo(1M)).
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 clus‐
ter; 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 speci‐
fied 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 ALSOmount(1M), umount(2), mnttab(4)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.
SunOS 5.10 26 Feb 2004 mount(2)
