vfsmount(2)

NAME

vfsmount — mount a file system

SYNOPSIS

#include <sys/mount.h> 

int vfsmount(int type, 
             const char *dir, 
             int flags, 
             caddr_t data); 

Remarks

This routine is included only for compatibility with past releases. It works only with UFS (HFS), NFS, and CDFS file systems. For maximum portability and improved functionality, new applications should use the mount() system call (see mount(2)).

DESCRIPTION

The vfsmount() system call attaches a file system to a directory. After a successful return, references to directory dir refer to the root directory of the newly mounted file system. dir is a pointer to a null-terminated string containing a path name. dir must exist already, and must be a directory. Its old contents are inaccessible while the file system is mounted.

type indicates the type of the file system. It must be one of the types described below. vfsmount() does not check that the file system is actually of type type; if type is incorrect, vfsmount() may cause the process to hang. To prevent such problems, statfsdev() (see statfsdev(3C)) should be called before vfsmount() to check the file system type, which statfsdev() places in the f_fsid[1] field of the statfs structure that it returns.

The flags argument determines whether the file system can be written to. It also controls whether programs from the mounted file system are allowed to have set-user-ID execution. Physically write-protected and magnetic tape file systems must be mounted read-only. Failure to do so results in a return of -1 by vfsmount() and a value of [EIO] in errno. The following values for the flags argument are defined in <sys/mount.h>:

M_RDONLY: Mount done as read-only.
M_NOSUID: Execution of set-user-ID programs not permitted.

data is a pointer to a structure containing arguments specific to the value contained in type. The following values for type are defined in <sys/mount.h>:

MOUNT_CDFS

Mount a local CD-ROM file system. data points to a structure of the following format:

struct cdfs_args { 
     char    *fspec; 
}; 

fspec points to the name of the block special file that is to be mounted.

MOUNT_UFS

Mount a local HFS file system. data points to a structure of the following format:

struct ufs_args { 
     char    *fspec; 
     int      flags; 
}; 

fspec points to the name of the block special file that is to be mounted. This is identical in use and function to the first argument of mount() (see mount(2)).

flags points to a bit map that sets options. The following values of the bits are defined in <sys/mount.h>:

MS_DELAY

Specify that the writes to disks are to be delayed till the buffer needs to be reused. This is the default.

MS_BEHIND

Specify that the writes to disks are to be done asynchronously, where possible, without waiting for completion.

MS_BEHIND and MS_DELAY are mutually exclusive.

MS_NO_FSASYNC

Specify that rigorous posting of file system metadata is to be used. This is the default.

MS_FSASYNC

Specify that relaxed posting of file system metadata is to be used. This may lead to better performance for certain applications; but there is increased potential for data loss in case of a crash.

MS_FSASYNC and MS_NO_FSASYNC are mutually exclusive.

Notes

The MOUNT_NFS type is no longer supported through this interface.

RETURN VALUE

vfsmount() returns the following values:

0: Successful completion.
-1: Failure. No file system is mounted. errno is set to indicate the error.

ERRORS

If vfsmount() fails, errno is set to one of the following values.

EBUSY: dir is not a directory, or another process currently holds a reference to it.
EBUSY: No space remains in the mount table.
EBUSY: The superblock for the file system had a bad magic number or an out-of-range block size.
EBUSY: Not enough memory was available to read the cylinder group information for the file system.
EFAULT: data or dir points outside the allocated address space of the process.
EINVAL: type is not MOUNT_UFS, or MOUNT_CDFS.
EIO: An I/O error occurred while reading from or writing to the file system.
EIO: An attempt was made to mount a physically write protected or magnetic tape file system as read-write.
ELOOP: Too many symbolic links were encountered while translating the path name of file system referred to by data or dir.
ENAMETOOLONG: The path name of the file system referred to by data or dir is longer than PATH_MAX bytes, or the length of a component of the path name exceeds NAME_MAX bytes while _POSIX_NO_TRUNC is in effect.
ENOENT: The file system referred to by data or dir does not exist.
ENOENT: The file system referred to by data does not exist.
ENOTBLK: The file system referred to by data is not a block device. This message can occur only during a local mount.
ENOTDIR: A component of the path prefix in dir is not a directory.
ENOTDIR: A component of the path prefix of the file system referred to by data or dir is not a directory.
ENXIO: The major device number of the file system referred to by data is out of range (indicating that no device driver exists for the associated hardware).
EPERM: The caller does not have appropriate privileges.

DEPENDENCIES

NFS

If vfsmount() fails, errno can also be set to one of the following values.

EFAULT: A pointer in the data structure points outside the process's allocated address space.
EINVAL: A value in a field of data is out of proper range.

See mountd(1M), getfh(2), and inet(7F) for more information.

WARNINGS

The mount command (see mount(1M)) is preferred over vfsmount() because mount supports all mounting options that are available from vfsmount() directly, plus mount also maintains the /etc/mnttab file which lists what file systems are mounted.

Obsolescent Interfaces

vfsmount() is to be obsoleted at a future date.

AUTHOR

vfsmount() was developed by HP and Sun Microsystems, Inc.