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.\"
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.\"     @(#)mount.8	8.7 (Berkeley) 3/27/94
.\"
.Dd March 27, 1994
.Dt MOUNT 8
.Os
.Sh NAME
.Nm mount
.Nd mount file systems
.Sh SYNOPSIS
.Nm mount
.Op Fl Aadfruvw
.Op Fl t Ar type
.Nm mount
.Op Fl dfruvw
.Ar special | node
.Nm mount
.Op Fl dfruvw
.Op Fl o Ar options
.Op Fl t Ar type
.Ar special node
.Sh DESCRIPTION
The
.Nm
command invokes a filesystem-specific program to prepare
and graft the
.Ar special
device or 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
A mount point
.Ar node
must be an existing directory for a mount to succeed
.Po
except in the special case of
.Pa / ,
of course
.Pc .
Only the superuser may mount filesystems unless
.Va kern.usermount
is nonzero
.Po
see
.Xr sysctl 8
.Pc .
.Pp
The options to
.Nm
are as follows:
.Bl -tag -width indent
.It Fl A
Causes
.Nm
to try to mount all of the file systems listed in the
.Xr fstab 5
table except those for which the
.Dq noauto
option is specified.
.It Fl a
Similar to the
.Fl A
flag, except that if a file system (other than the root file system)
appears to be already mounted,
.Nm
will not try to mount it again.
.Nm
assumes that a file system is already mounted if a file system with
the same type is mounted on the given mount point.
More stringent checks are not possible because some file system types
report strange values for the mounted-from device for mounted file
systems.
.It Fl d
Causes everything to be done except for the invocation of
the filesystem-specific program.
This option is useful in conjunction with the
.Fl v
flag to
determine what the
.Nm
command is trying to do.
.It Fl f
Either force mounting of dirty filesystems or, in the case of an
downgrade from read-write to read-only operation, the revocation of
opened files with write access.
.It Fl o Ar options
Options are specified with a
.Fl o
flag followed by a comma separated string of options.
The options are as follows:
.Bl -tag -width indent
.It async
All
.Tn I/O
to the file system should be done asynchronously.
This is a
.Em dangerous
flag to set since it does not guarantee to keep a consistent
file system structure on the disk.
You should not use this flag
unless you are prepared to recreate the file system should your
system crash.
The most common use of this flag is to speed up
.Xr restore 8
where it can give a factor of two speed increase.
.It force
The same as
.Fl f ;
forces the revocation of write access when trying to downgrade
a filesystem mount status from read-write to read-only.
.It noatime
Do not update atime on files in the system unless the mtime or ctime
is being changed as well.
This option is useful for laptops and news servers where one does
not want the extra disk activity associated with updating the atime.
.It noaccesstime
Synonym for noatime provided for compatibility with
other operating systems.
.It nodev
Do not interpret character or block special devices on the file system.
This option is useful for a server that has file systems containing
special devices for architectures other than its own.
.It noexec
Do not allow execution of any binaries on the mounted file system.
This option 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 rdonly
The same as
.Fl r ;
mount the file system read-only (even the superuser may not write it).
.It sync
All
.Tn I/O
to the file system should be done synchronously.
.It update
The same as
.Fl u ;
indicate that the status of an already mounted file system should be changed.
.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
.Pp
Any additional options specific to a given filesystem type (see the
.Fl t
option) may be passed as a comma separated list; these options are
distinguished by a leading
.Dq \&-
(dash).
Options that take a value are specified using the syntax -option=value.
For example, the
.Nm
command:
.Bd -literal -offset indent
mount -t mfs -o nosuid,-N,-s=4000 /dev/dk0b /tmp
.Ed
.Pp
causes
.Nm
to execute the equivalent of:
.Bd -literal -offset indent
/sbin/mount_mfs -o nosuid -N -s 4000 /dev/dk0b /tmp
.Ed
.It Fl r
The file system is to be mounted read-only.
Mount the file system read-only (even the superuser may not write it).
The same as the
.Dq rdonly
argument to the
.Fl o
option.
.It Fl t Ar type
The argument following the
.Fl t
is used to indicate the file system type.
The type
.Ar ffs
is the default.
The
.Fl t
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
.Dq no
to specify the filesystem types for which action should
.Em not
be taken.
For example, the
.Nm
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
.Nm
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 5
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.
.El
.Pp
The options specific to the various file system types are
described in the manual pages for those file systems'
.Nm mount_XXX
commands.
For instance, the options specific to Berkeley
Fast File Systems are described in the
.Xr mount_ffs 8
manual page.
.Sh EXAMPLES
.Bd -literal
mount -t cd9660 -r /dev/cd0a /mnt/cdrom
mount -t msdos /dev/fd0a /mnt/floppy
mount host:/path/name /mnt/nfs
.Pp
.Sh FILES
.Bl -tag -width /etc/fstab -compact
.It Pa /etc/fstab
file system table
.El
.Sh SEE ALSO
.Xr mount 2 ,
.Xr fstab 5 ,
.Xr mount_ados 8 ,
.Xr mount_cd9660 8 ,
.Xr mount_fdesc 8 ,
.Xr mount_ffs 8 ,
.Xr mount_kernfs 8 ,
.Xr mount_mfs 8 ,
.Xr mount_msdos 8 ,
.Xr mount_nfs 8 ,
.Xr mount_null 8 ,
.Xr mount_portal 8 ,
.Xr mount_procfs 8 ,
.Xr mount_umap 8 ,
.Xr mount_union 8 ,
.Xr mount_xfs 8 ,
.Xr sysctl 8 ,
.Xr umount 8
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .