mount - mount file systems
mount [-Aadfruvw] [-t type]
mount [-dfruvw] special | node
mount [-dfruvw] [-o options] [-t type] special node
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
partition
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
mount.
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
asynchronously.
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.
softdep
(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
on-disk
state of the file system consistent. This
results in
significant speedups for file create/delete
operations.
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.
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.
noaccesstime
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
synchronously.
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
/tmp
causes mount to execute the equivalent of:
# /sbin/mount_mfs -o nosuid -s 4000 /dev/sd0b
/tmp
-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
command:
# mount -a -t nonfs,mfs
mounts all file systems except those of type NFS and
MFS.
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.
/etc/fstab file system table
# mount -t cd9660 -r /dev/cd0a /mnt/cdrom
# mount -t msdos /dev/fd0a /mnt/floppy
# mount host:/path/name /mnt/nfs
mount(2), fstab(5), disklabel(8), mount_ados(8),
mount_cd9660(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_null(8),
mount_portal(8), mount_procfs(8), mount_umap(8),
mount_union(8),
mount_xfs(8), sysctl(8), umount(8)
A mount command appeared in Version 3 AT&T UNIX.
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
all).
OpenBSD 3.6 March 27, 1994
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