sbin/mount/mount.8

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.\"     @(#)mount.8	8.8 (Berkeley) 6/16/94
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.Dd May 21, 2002
.Dt MOUNT 8
.Os
.Sh NAME
.Nm mount
.Nd mount file systems
.Sh SYNOPSIS
.Nm
.Op Fl Aadfruvw
.Op Fl t Ar type
.Nm ""
.Op Fl dfruvw
.Ar special | node
.Nm ""
.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. The provided argument is looked up first in the
.Dq fs_file ,
then in the
.Dq fs_spec
column.
If both
.Ar special
and
.Ar node
are given, the disklabel is checked for the filesystem type.
.Pp
In
.Nx ,
a file system can only be mounted by an ordinary user who owns the
point
.Ar node
and has access to the
.Ar special
device (at least read permissions).  In addition, the
.Em vfs.generic.usermount
.Xr sysctl 3
must be set to 1 to permit file system mounting by ordinary users.
See also
.Xr sysctl 8 .
.Pp
The system maintains a list of currently mounted file systems.
If no arguments are given to
.Nm "" ,
this list is printed.
.Pp
The options 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
file 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
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 are available:
.Bl -tag -width nocoredump
.It Cm async
All
.Tn I/O
to the file system should be done asynchronously.
In the event of a crash,
.Em "it is impossible for the system to verify the integrity of data on a file system mounted with this option" .
You should only use this
option if you have an application-specific data
recovery mechanism, or are willing to recreate the file system from
scratch.
.It Cm noasync
Clear
.Cm async
mode.
.It Cm 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 Cm noatime
Never update the access time field for files.
This option is useful for optimizing read performance on filesystems
that are used as news spools.
.It Cm noauto
This filesystem should be skipped when mount is run with the
.Fl a
flag.
.It Cm 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 Cm nodevmtime
Do not update modification times on device special files.  This option
is useful on laptops or other systems that perform power management.
.It Cm nocoredump
Do not allow programs to create crash dumps (core files) on the file system.
This option can be used to help protect sensitive
data by keeping core files (which may contain sensitive data)
from being created on insecure file systems.
Only core files that would be created by program crashes are
prevented by use of this flag; the behavior of
.Xr savecore 8
is not affected.
.It Cm 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 Cm nosuid
Do not allow set-user-identifier or set-group-identifier bits to take effect.
.It Cm rdonly
The same as
.Fl r ;
mount the file system read-only (even the super-user may not write it).
.It Cm softdep
(FFS only) Mount the filesystem using soft-dependencies. This means that
metadata will not be written immediately, but is written in an ordered fashion
to keep the on-disk state of the filesystem consistent. This results
in significant speedups for file create/delete operations. This option
will be ignored when using the
.Fl u
flag and a filesystem is already mounted read/write. This option has gone
through moderate to heavy testing, but should still be used with care.
It requires the
.Dv SOFTDEP
option to be enabled in the running kernel.
.It Cm symperm
Recognize permission of symbolic link when reading or traversing link.
.It Cm sync
All
.Tn I/O
to the file system should be done synchronously. This is not equivalent to the
normal mode in which only metadata is written synchronously.
.It Cm nosync
Clear
.Cm sync
mode.
.It Cm update
The same as
.Fl u ;
indicate that the status of an already mounted file system should be changed.
.It Cm 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, except for the fdesc
file system.
.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 mount command:
.Bd -literal -offset indent
mount -t mfs -o nosuid,-N,-s=32m swap /tmp
.Ed
.Pp
causes
.Nm
to execute the equivalent of:
.Bd -literal -offset indent
/sbin/mount_mfs -o nosuid -N -s 32m swap /tmp
.Ed
.It Fl r
The file system is to be mounted read-only.
Mount the file system read-only (even the super-user 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 \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
.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
file, 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 System (FFS) are described in the
.Xr mount_ffs 8
manual page.
.Pp
The particular type of filesystem in each partition of a disk can
be found by examining the disk label with the
.Xr disklabel 8
command.
.Sh FILES
.Bl -tag -width /etc/fstab -compact
.It Pa /etc/fstab
file system table
.El
.Sh EXAMPLES
Some useful examples:
.Pp
.Bl -hang -offset indent -width "MS-DOS"
.It Tn CD-ROM
.br
mount -t cd9660 -r /dev/cd0a /cdrom
.It Tn MS-DOS
.br
mount -t msdos /dev/fd0a /floppy
.It Tn NFS
.br
mount nfs-server-host:/directory/path /mount-point
.It Tn MFS (32 megabyte)
.br
mount -t mfs -o nosuid,-s=32m swap /tmp
.El
.Pp
The "noauto" directive in
.Pa /etc/fstab
can be used to make it easy to manually mount and unmount removeable
media using just the mountpoint filename, with an entry like this:
.Pp
.Dl /dev/cd0a  /cdrom  cd9660 ro,noauto 0 0
.Pp
That would allow a simple command like
.Qq mount /cdrom
or
.Qq umount /cdrom
for media using the
.Tn ISO-9660
filesystem format in the first
.Tn CD-ROM
drive.
.Sh SEE ALSO
.Xr mount 2 ,
.Xr fstab 5 ,
.Xr disklabel 8 ,
.Xr mount_ados 8 ,
.Xr mount_cd9660 8 ,
.Xr mount_ext2fs 8 ,
.Xr mount_fdesc 8 ,
.Xr mount_ffs 8 ,
.Xr mount_filecore 8 ,
.Xr mount_kernfs 8 ,
.Xr mount_lfs 8 ,
.Xr mount_mfs 8 ,
.Xr mount_msdos 8 ,
.Xr mount_nfs 8 ,
.Xr mount_ntfs 8 ,
.Xr mount_null 8 ,
.Xr mount_overlay 8 ,
.Xr mount_portal 8 ,
.Xr mount_procfs 8 ,
.Xr mount_umap 8 ,
.Xr mount_union 8 ,
.Xr umount 8
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .