sbin/mount/mount.8

.\" Copyright (c) 1980, 1989, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.roff%
.\"
.\"     @(#)mount.8	6.20 (Berkeley) 04/06/93
.\"
.Dd
.Dt MOUNT 8
.Os BSD 4
.Sh NAME
.Nm mount ,
.Nm umount
.Nd mount and dismount file systems
.Sh SYNOPSIS
.Nm mount
.Op Fl afrwu
.Op Fl t Ar ufs | lfs | external_type
.Nm mount
.Op Fl frwu
.Ar special | node
.Nm mount
.Op Fl frwu
.Op Fl t Ar ufs | lfs | external_type
.Op Fl o Ar options
.Ar special node
.Nm umount
.Op Fl af
.Op Fl t Ar ufs | lfs | external_type
.Nm umount
.Op Fl f
.Ar special | node
.Sh DESCRIPTION
The
.Nm mount
command
calls the
.Xr mount 2
system call to prepare and graft a
.Ar special
device or the remote node
(rhost:path)
on to the file system tree at the point
.Ar node.
If either
.Ar special
or
.Ar node
are not provided, the appropriate
information is taken from the
.Xr fstab 5
file.
.Pp
The system maintains a list of currently mounted file systems.
If no arguments are given to
.Nm mount,
this list is printed.
.Pp
Options available for the
.Nm mount
command:
.Bl -tag -width indent
.It Fl F
The standard mount options are parsed and
passed to external program via the
.Fl F
option
as a decimal number.
(See example below.)
.It Fl d
Causes everything to be done except for the actual system call.
This option is useful in conjunction with the
.Fl v
flag to
determine what the
.Nm mount
command is trying to do.
.It Fl f
Forces the revocation of write access when trying to downgrade
a filesystem mount status from read-write to read-only.
.It Fl o
Options are specified with a
.Fl o
flag
followed by a comma separated string of options.
The following options apply to any file system that is being mounted:
.Bl -tag -width indent
.It noexec
Do not allow execution of any binaries on the mounted file system.
This options is useful for a server that has file systems containing
binaries for architectures other than its own.
.It nosuid
Do not allow set-user-identifier or set-group-identifier bits to take effect.
.It nodev
Do not interpret character or block special devices on the file system.
This options is useful for a server that has file systems containing
special devices for architectures other than its own.
.It synchronous
All
.Tn I/O
to the file system should be done synchronously.
.It union
Causes the namespace at the mount point to appear as the union
of the mounted filesystem root and the existing directory.
Lookups will be done in the mounted filesystem first.
If those operations fail due to a non-existent file the underlying
directory is then accessed.
All creates are done in the mounted filesystem.
.El
.It Fl r
The file system object is to be mounted read-only.
.It Fl t Ar "ufs \\*(Ba lfs \\*(Ba external type"
The argument following the
.Fl t
is used to indicate the file system type.
The type
.Ar ufs
is the default.
The \fI-t\fP option can be used
to indicate that the actions should only be taken on
filesystems of the specified type.
More than one type may be specified in a comma separated list.
The list of filesystem types can be prefixed with ``no'' to
specify the filesystem types on which no action should be taken.
For example, the
.Nm mount
command:
.Bd -literal -offset indent
mount -a -t nonfs,mfs
.Ed
.Pp
mounts all filesystems except those of type
.Tn NFS
and
.Tn MFS .
.Pp
If the type is not one of the internally known types,
mount will attempt to execute a program in
.Pa /sbin/mount_ Ns Em XXX
where
.Em XXX
is replaced by the type name.
For example, nfs filesystems are mounted by the program
.Pa /sbin/mount_nfs .
.It Fl u
The
.Fl u
flag indicates that the status of an already mounted file
system should be changed.
Any of the options discussed above (the
.Fl o
option)
may be changed;
also a file system can be changed from read-only to read-write
or vice versa.
An attempt to change from read-write to read-only will fail if any
files on the filesystem are currently open for writing unless the
.Fl f
flag is also specified.
The set of options is determined by first extracting the options
for the file system from the
.Xr fstab
table,
then applying any options specified by the
.Fl o
argument,
and finally applying the
.Fl r
or
.Fl w
option.
.It Fl v
Verbose mode.
.It Fl w
The file system object is to be read and write.
.It Fl
Any additional options specific to the program can
be passed as a comma separated list;
these options are distinguished by starting with a
.Fl
(dash).
.El
.Pp
Those options that take a value are specified
using the syntax -option=value.
For example, the mount command:
.Bd -literal -offset indent
mount -t mfs -o nosuid,-N,-s=4000 /dev/dk0b /tmp
.Ed
.Pp
causes mount to attempt to execute:
.Bd -literal -offset indent
/sbin/mount_mfs -F 8 -N -s 4000 /dev/dk0b /tmp
.Ed
.Pp
The options specific to NFS filesystems are described in the
.Xr mount_nfs 8
manual page.
.Pp
.Nm Umount
removes the
.Ar special
device grafted at point
.Ar node
from file system tree.
.Pp
Options for the
.Nm umount
command:
.Bl -tag -width indent
.It Fl f
The file system is forcibly unmounted.
Active special devices continue to work,
but all other files return errors if further accesses are attempted.
The root file system cannot be forcibly unmounted.
.It Fl a
All of the file systems described in
.Xr fstab 5
are unmounted.
.It Fl t
Is used to indicate the actions should only be taken on
filesystems of the specified type.
More than one type may be specified in a comma separated list.
The list of filesystem types can be prefixed with ``no'' to
specify the filesystem types on which no action should be taken.
(See example above for the
.Nm mount
command.)
.El
.Sh FILES
.Bl -tag -width /etc/fstab -compact
.It Pa /etc/fstab
file system table
.El
.Sh SEE ALSO
.Xr mount 2 ,
.Xr unmount 2 ,
.Xr fstab 5
.Sh BUGS
It is possible for a corrupted file system to cause a crash.
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .