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[unix-history] / usr / src / lib / libc / sys / mount.2

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.\" by the University of California, Berkeley.  The name of the
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.\"	@(#)mount.2	6.8 (Berkeley) %G%
.\"
.TH MOUNT 2 ""
.UC 4
.SH NAME
mount, unmount \- mount or remove file system
.SH SYNOPSIS
.nf
#include <sys/mount.h>
.sp
.ft B
mount(type, dir, flags, data)
int type;
char *dir;
int flags;
caddr_t data;
.PP
.ft B
unmount(dir, flags)
char *dir;
int flags;
.fi
.SH DESCRIPTION
.I Mount
announces to the system that a file system has
been mounted on the directory
.IR dir ;
following the mount, references to directory
.I dir
will refer to
the root directory on the newly mounted file system.
.I Dir
is a pointer to a null-terminated string
containing the appropriate path name
which must be a directory that already exists.
Its old contents are inaccessible while the
file system is mounted.
.PP
The
.I flag
argument determines whether certain semantics should be
suppressed when accessing the file system:
.IP M_RDONLY 14
The file system should be treated as read-only;
no writing is allowed (even by the super-user).
Physically write-protected and magnetic
tape file systems must be mounted read-only or
errors will occur when access times are updated,
whether or not any
explicit write is attempted.
.IP M_NOEXEC 14
Do not allow files to be executed from the file system.
.IP M_NOSUID 14
Do not honor setuid or setgid bits on files when executing them.
.IP M_NODEV 14
Do not interpret special files on the file system.
.IP M_SYNCHRONOUS 14
All I/O to the file system should be done synchronously.
.PP
The flag M_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.
.PP
The
.I type
argument defines the type of the file system.
The types of file systems known to the system are defined in
.IR mount.h .
.I 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:
.IP MOUNT_UFS 6
.nf
.ta \w'struct  'u +\w'nfsv2fh_t  'u +\w'sockaddr_in *addr  'u
struct ufs_args {
	char	*fspec;	/* Block special file to mount */
};
.fi
.sp
.IP MOUNT_NFS 6
.nf
struct nfs_args {
	struct	sockaddr_in *addr;	/* file server address */
	nfsv2fh_t	*fh;	/* File handle to be mounted */
	int	flags;	/* flags */
	int	wsize;	/* write size in bytes */
	int	rsize;	/* read size in bytes */
	int	timeo;	/* initial timeout in 0.1 secs */
	int	retrans;	/* times to retry send */
	char	*hostname;	/* server's name */
};
.fi
.IP MOUNT_MFS 6
.nf
struct mfs_args {
	char	*name;	/* name of backing process */
	caddr_t	base;	/* base address of the file system */
	u_long	size;	/* size of the file system */
};
.fi
.sp
.PP
.I Umount
announces to the system that the file system mounted at
.I dir
is no longer to contain that file system.
The associated directory reverts to its ordinary interpretation.
.PP
The
.I flags
argument may have the following values:
.IP MNT_NOFORCE 12
The unmount should fail if any files are active on the file system.
.IP MNT_FORCE 12
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.
.SH "RETURN VALUE
.I Mount
returns 0 if the action occurred, \-1 if an error occurred.
The mount can fail if
.I dir
does not exist or is not a directory.
For a
.I ufs
file system, the mount can fail if the special device
specified in the ufs_args structure is
inaccessible, is not an appropriate file, or is already mounted.
A
.I ufs
or
.I mfs
mount can also fail if there are already too many
file systems mounted.
.PP
.I Umount
returns 0 if the action occurred; \-1 if an error occurred.
The unmount will fail
if there are active files in the mounted file system.
.SH ERRORS
.I Mount
will fail when one of the following occurs:
.TP 15
[EPERM]
The caller is not the super-user.
.TP 15
[ENAMETOOLONG]
A component of a pathname exceeded 255 characters,
or the entire length of a path name exceeded 1023 characters.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating a pathname.
.TP 15
[ENOENT]
A component of \fIdir\fP does not exist.
.TP 15
[ENOTDIR]
A component of \fIname\fP is not a directory,
or a path prefix of \fIspecial\fP is not a directory.
.TP 15
[EINVAL]
A pathname contains a character with the high-order bit set.
.TP 15
[EBUSY]
Another process currently holds a reference to
.IR dir .
.TP 15
[EFAULT]
\fIDir\fP points outside the process's allocated address space.
.PP
The following errors can occur for a
.I ufs
file system mount:
.TP 15
[ENODEV]
A component of ufs_args \fIfspec\fP does not exist.
.TP 15
[ENOTBLK]
.I Fspec
is not a block device.
.TP 15
[ENXIO]
The major device number of 
.I fspec
is out of range (this indicates no device driver exists
for the associated hardware).
.TP 15
[EBUSY]
\fIFspec\fP is already mounted.
.TP 15
[EMFILE]
No space remains in the mount table.
.TP 15
[EINVAL]
The super block for the file system had a bad magic
number or an out of range block size.
.TP 15
[ENOMEM]
Not enough memory was available to read the cylinder
group information for the file system.
.TP 15
[EIO]
An I/O error occurred while reading the super block or
cylinder group information.
.TP 15
[EFAULT]
\fIFspec\fP points outside the process's allocated address space.
.PP
The following errors can occur for a
.I nfs
file system mount:
.TP 15
[ETIMEDOUT]
.I Nfs
timed out trying to contact the server.
.TP 15
[EFAULT]
Some part of the information described by nfs_args
points outside the process's allocated address space.
.PP
The following errors can occur for a
.I mfs
file system mount:
.TP 15
[EMFILE]
No space remains in the mount table.
.TP 15
[EINVAL]
The super block for the file system had a bad magic
number or an out of range block size.
.TP 15
[ENOMEM]
Not enough memory was available to read the cylinder
group information for the file system.
.TP 15
[EIO]
An paging error occurred while reading the super block or
cylinder group information.
.TP 15
[EFAULT]
\fIName\fP points outside the process's allocated address space.
.PP
.I Umount
may fail with one of the following errors:
.TP 15
[EPERM]
The caller is not the super-user.
.TP 15
[ENOTDIR]
A component of the path is not a directory.
.TP 15
[EINVAL]
The pathname contains a character with the high-order bit set.
.TP 15
[ENAMETOOLONG]
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 characters.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating the pathname.
.TP 15
[EINVAL]
The requested directory is not in the mount table.
.TP 15
[EBUSY]
A process is holding a reference to a file located
on the file system.
.TP 15
[EIO]
An I/O error occurred while writing cached file system information.
.TP 15
[EFAULT]
\fIDir\fP points outside the process's allocated address space.
.SH "SEE ALSO"
mount(8), umount(8), mfs(8)
.SH BUGS
Some of the error codes need translation to more obvious messages.