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MOUNT(2) BSD System Calls Manual MOUNT(2) NAME mount, unmount -- mount or dismount a file system LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <sys/param.h> #include <sys/mount.h> int mount(const char *type, const char *dir, int flags, void *data); int unmount(const char *dir, int flags); DESCRIPTION The mount() function grafts a file system object onto the system file tree at the point dir. The argument data describes the file system ob- ject to be mounted. The argument type tells the kernel how to interpret data (See type below). The contents of the file system become available through the new mount point dir. Any files in dir at the time of a suc- cessful mount are swept under the carpet so to speak, and are unavailable until the file system is unmounted. The following flags may be specified to suppress default semantics which affect file system access. MNT_RDONLY The file system should be treated as read-only; Even the super-user may not write on it. Specifying MNT_UPDATE without this option will upgrade a read-only file system to read/write. MNT_NOEXEC Do not allow files to be executed from the file system. MNT_NOSUID Do not honor setuid or setgid bits on files when execut- ing them. MNT_NOATIME Disable update of file access times. MNT_NODEV Do not interpret special files on the file system. MNT_SUIDDIR Directories with the SUID bit set chown new files to their own owner. MNT_SYNCHRONOUS All I/O to the file system should be done synchronously. MNT_ASYNC All I/O to the file system should be done asyn- chronously. MNT_FORCE Force a read-write mount even if the file system appears to be unclean. Dangerous. MNT_NOCLUSTERR Disable read clustering. MNT_NOCLUSTERW Disable write clustering. The flag MNT_UPDATE indicates that the mount command is being applied to an already mounted file system. This allows the mount flags to be changed without requiring that the file system be unmounted and re- mounted. Some file systems may not allow all flags to be changed. For example, many file systems will not allow a change from read-write to read-only. The flag MNT_RELOAD causes the vfs subsystem to update its data struc- tures pertaining to the specified already mounted file system. The type argument names the file system. The types of file systems known to the system can be obtained with lsvfs(1). Data is a pointer to a structure that contains the type specific argu- ments to mount. The format for these argument structures is described in the manual page for each file system. By convention file system manual pages are named by prefixing ``mount_'' to the name of the file system as returned by lsvfs(1). Thus the NFS file system is described by the mount_nfs(8) manual page. The unmount() function call disassociates the file system from the speci- fied mount point dir. The flags argument may specify MNT_FORCE to specify that the file system should be forcibly unmounted or made read-only (if MNT_UPDATE and MNT_RDONLY are also specified) even if files are still active. Active special devices continue to work, but any further accesses to any other active files result in errors even if the file system is later remounted. The MNT_SUIDDIR option requires the SUIDDIR option to have been compiled into the kernel to have any effect. See the mount(8) and chmod(2) pages for more information. RETURN VALUES Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error. ERRORS The mount() function will fail when one of the following occurs: [EPERM] The caller is not the super-user. [ENAMETOOLONG] A component of a pathname exceeded 255 characters, or the entire length of a path name exceeded 1023 charac- ters. [ELOOP] Too many symbolic links were encountered in translat- ing a pathname. [ENOENT] A component of dir does not exist. [ENOTDIR] A component of name is not a directory, or a path pre- fix of special is not a directory. [EBUSY] Another process currently holds a reference to dir. [EFAULT] Dir points outside the process's allocated address space. The following errors can occur for a ufs file system mount: [ENODEV] A component of ufs_args fspec does not exist. [ENOTBLK] Fspec is not a block device. [ENXIO] The major device number of fspec is out of range (this indicates no device driver exists for the associated hardware). [EBUSY] Fspec is already mounted. [EMFILE] No space remains in the mount table. [EINVAL] The super block for the file system had a bad magic number or an out of range block size. [ENOMEM] Not enough memory was available to read the cylinder group information for the file system. [EIO] An I/O error occurred while reading the super block or cylinder group information. [EFAULT] Fspec points outside the process's allocated address space. The following errors can occur for a nfs file system mount: [ETIMEDOUT] Nfs timed out trying to contact the server. [EFAULT] Some part of the information described by nfs_args points outside the process's allocated address space. The unmount() function may fail with one of the following errors: [EPERM] The caller is not the super-user. [ENOTDIR] A component of the path is not a directory. [ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters. [ELOOP] Too many symbolic links were encountered in translat- ing the pathname. [EINVAL] The requested directory is not in the mount table. [EBUSY] A process is holding a reference to a file located on the file system. [EIO] An I/O error occurred while writing cached file system information. [EFAULT] Dir points outside the process's allocated address space. A ufs mount can also fail if the maximum number of file systems are cur- rently mounted. SEE ALSO lsvfs(1), mount(8), umount(8) BUGS Some of the error codes need translation to more obvious messages. HISTORY Mount() and unmount() function calls appeared in Version 6 AT&T UNIX. BSD May 24, 1995 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | BUGS | HISTORY
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