mount, unmount - mount or dismount a file system
Standard C Library (libc, -lc)
#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);
The mount() function grafts a file system object onto the system file
tree at the point dir. The argument data describes the file system
object 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 successful 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.
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 executing
them.
MNT_NODEV Do not interpret special files on the file system.
MNT_UNION Union with underlying filesystem instead of obscuring
it.
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 asynchronously.
MNT_NOCOREDUMP Do not allow programs to dump core files on the file
system.
MNT_NOATIME Never update access time in the file system.
MNT_SYMPERM Recognize the permission of symbolic link when reading
or traversing.
MNT_NODEVMTIME Never update modification time of device files.
MNT_SOFTDEP Use soft dependencies.
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
remounted. Some file systems may not allow all flags to be changed. For
example, most file systems will not allow a change from read-write to
read-only.
The type argument defines the type of the file system. The types of file
systems known to the system are defined in <sys/mount.h>. data is a
pointer to a structure that contains the type specific arguments to
mount. The currently supported types of file systems and their type specific
data are:
MOUNT_FFS
struct ufs_args {
char *fspec; /* block special file to mount */
struct export_args export; /* network export information */
};
MOUNT_NFS
struct nfs_args {
int version; /* args structure version */
struct sockaddr *addr; /* file server address */
int addrlen; /* length of address */
int sotype; /* Socket type */
int proto; /* and Protocol */
u_char *fh; /* File handle to be mounted */
int fhsize; /* Size, in bytes, of fh */
int flags; /* flags */
int wsize; /* write size in bytes */
int rsize; /* read size in bytes */
int readdirsize; /* readdir size in bytes */
int timeo; /* initial timeout in .1 secs */
int retrans; /* times to retry send */
int maxgrouplist; /* Max. size of group list */
int readahead; /* # of blocks to readahead */
int leaseterm; /* Term (sec) of lease */
int deadthresh; /* Retrans threshold */
char *hostname; /* server's name */
};
MOUNT_MFS
struct mfs_args {
char *fspec; /* name to export for statfs */
struct export_args export; /* if we can export an MFS */
caddr_t base; /* base of file system in mem */
u_long size; /* size of file system */
};
The unmount() function call disassociates the file system from the specified
mount point dir.
The flags argument may specify MNT_FORCE to specify that the file system
should be forcibly unmounted 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.
mount() returns the value 0 if the mount was successful, otherwise -1 is
returned and the variable errno is set to indicate the error.
unmount() returns the value 0 if the unmount succeeded; otherwise -1 is
returned and the variable errno is set to indicate the error.
mount() will fail when one of the following occurs:
[EPERM] The caller is not the super-user.
[ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} characters,
or an entire path name exceeded {PATH_MAX} characters.
[ELOOP] Too many symbolic links were encountered in translating
a pathname.
[ENOENT] A component of dir does not exist.
[ENOTDIR] A component of name is not a directory, or a path prefix
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 following errors can occur for a mfs file system mount:
[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] A paging error occurred while reading the super block
or cylinder group information.
[EFAULT] Name points outside the process's allocated address
space.
unmount() 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 {NAME_MAX} characters,
or an entire path name exceeded {PATH_MAX} characters.
[ELOOP] Too many symbolic links were encountered in translating
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 or mfs mount can also fail if the maximum number of file systems
are currently mounted.
getfsstat(2), getmntinfo(3), symlink(7), mount(8), sysctl(8), umount(8)
The mount() and umount() (now unmount()) function calls appeared in
Version 6 AT&T UNIX.
Some of the error codes need translation to more obvious messages.
BSD November 7, 1999 BSD
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