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NAME    [Toc]    [Back]

     mount - mount file systems

SYNOPSIS    [Toc]    [Back]

     mount [-Aadfruvw] [-t type]
     mount [-dfruvw] special | node
     mount [-dfruvw] [-o options] [-t type] special node

DESCRIPTION    [Toc]    [Back]

     The mount command invokes a file system specific program  to
prepare and
     graft  the  special device or remote node (rhost:path) on to
the file system
 tree at the point node.  If either special or  node  are
not provided,
     the appropriate information is taken from the fstab(5) file.

     For disk partitions, the special device must correspond to a
     registered in the disklabel(5).

     The  system  maintains a list of currently mounted file systems.  If no arguments
 are given to mount, this list is printed.

     A mount point node must be an existing directory for a mount
to succeed
     (except  in the special case of /, of course).  Only the superuser may
     mount file systems unless  kern.usermount  is  nonzero  (see
sysctl(8)), the
     special  device  is  readable  and writeable by the user attempting the
     mount, and the mount point node is owned  by  the  user  attempting the

     The options are as follows:

     -A      Causes mount to try to mount all of the file systems
listed in
             the  fstab(5)  table  except  those  for  which  the
``noauto'' option
             is specified.

     -a      Similar to the -A flag, except that if a file system
(other than
             the root file system) appears to be already mounted,
mount will
             not  try  to  mount  it again.  mount 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.

     -d       Causes everything to be done except for the invocation of the
             file system specific program.  This option is useful
in conjunction
  with  the  -v flag to determine what the mount
command is trying
 to do.

     -f      Either force mounting of dirty file systems  or,  in
the case of a
             downgrade  from  read-write  to read-only operation,
the revocation
             of opened files with write access.

     -o options
             Options are specified with a -o flag followed  by  a
comma separated
 string of options.  Available options are as follows:

             async   All I/O to the file system  should  be  done
                     This  is  a  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
                     restore(8) where it can give a factor of two
speed increase.

                     (FFS  only.)   Mount  the  file system using
soft dependencies.
  Instead of metadata being written immediately, it
                     is written in an ordered fashion to keep the
                     state of the file system  consistent.   This
results in
                     significant  speedups for file create/delete
                     This option will be ignored when  using  the
-u flag and a
                     file  system  is already mounted read/write.
It requires
                     option FFS_SOFTUPDATES to be enabled in  the
running kernel.

             force    The  same  as  -f; forces the revocation of
write access
                     when trying to downgrade a file system mount
status from
                     read-write to read-only.

                     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

                     Synonym for noatime provided for compatibility with other
                     operating systems.

             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.

             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.

             nosuid  Do not  allow  set-user-identifier  or  setgroup-identifier
                     bits to take effect.

             rdonly   The same as -r; mount the file system readonly (even the
                     superuser may not write it).

             sync    All I/O to the file system  should  be  done

             update   The same as -u; indicate that the status of
an already
                     mounted file system should be changed.

             union   Causes the namespace at the mount  point  to
appear as the
                     union  of  the  mounted file system root and
the existing
                     directory.  Lookups  will  be  done  in  the
mounted file system
  first.  If those operations fail due to
a non-existent
 file the underlying directory  is  then
accessed.  All
                     creates are done in the mounted file system.

             Any additional options specific to a given file system type (see
             the  -t  option)  may be passed as a comma separated
list; these options
 are distinguished by a leading  ``-''  (dash).
Options that
             take  a  value  are  specified using the syntax -option=value.  For
             example, the mount command:

                   # mount -t  mfs  -o  nosuid,-s=4000  /dev/sd0b

             causes mount to execute the equivalent of:

                   #  /sbin/mount_mfs -o nosuid -s 4000 /dev/sd0b

     -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 ``rdonly'' argument to the -o option.

     -t type
             The argument following the -t is  used  to  indicate
the file system
             type.   The  type ffs is the default.  The -t option
can be used to
             indicate that the actions should only  be  taken  on
file systems of
             the specified type.  More than one type may be specified in a
             comma separated list.  The list of file system types
can be prefixed
  with  ``no'' to specify the file system types
for which action
 should not be taken.  For  example,  the  mount

                   # mount -a -t nonfs,mfs

             mounts all file systems except those of type NFS and

             mount  will  attempt  to  execute   a   program   in
/sbin/mount_XXX where
             XXX  is replaced by the type name.  For example, NFS
file systems
             are mounted by the program /sbin/mount_nfs.

     -u      The -u flag indicates that the status of an  already
mounted file
             system  should  be changed.  Any of the options discussed above
             (the -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 file
             system  are currently open for writing unless the -f
flag is also
             specified.  Only options specified  on  the  command
line with -o
             are  changed;  other  file  system options are unaltered.  The options
 set in the fstab(5) table are ignored.

     -v      Verbose mode.

     -w      The file system object is to be read and write.

     The options specific to the various file  system  types  are
described in
     the manual pages for those file systems' mount_XXX commands.
For instance,
 the options specific to Berkeley Fast  File  Systems
are described
     in the mount_ffs(8) manual page.

FILES    [Toc]    [Back]

     /etc/fstab  file system table

EXAMPLES    [Toc]    [Back]

     # mount -t cd9660 -r /dev/cd0a /mnt/cdrom

     # mount -t msdos /dev/fd0a /mnt/floppy

     # mount host:/path/name /mnt/nfs

SEE ALSO    [Toc]    [Back]

     mount(2),     fstab(5),     disklabel(8),     mount_ados(8),
     mount_ext2fs(8), mount_fdesc(8),  mount_ffs(8),  mount_kernfs(8),
     mount_mfs(8),  mount_msdos(8),  mount_nfs(8), mount_ntfs(8),
     mount_portal(8),       mount_procfs(8),       mount_umap(8),
     mount_xfs(8), sysctl(8), umount(8)

HISTORY    [Toc]    [Back]

     A mount command appeared in Version 3 AT&T UNIX.

CAVEATS    [Toc]    [Back]

     After  a  successful  mount, the permissions on the original
mount point determine
 if ``..'' is accessible from the mounted  file  system.  The minimum
 permissions for the mount point for traversal across the
mount point
     in both directions to be possible for all users is 0111 (execute for

OpenBSD      3.6                          March      27,     1994
[ Back ]
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