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
. If either
are not provided, the appropriate
information is taken from the
For disk partitions, the special
(DUID) or an entry in /dev
. If it is a DUID, it
will be automatically mapped to the appropriate entry in
. In either case the partition must be
present in the disklabel loaded from the device. The partition name is the
last letter in the entry name. For example, /dev/sd0a and 3eb7f9da875cb9ee.a
both refer to the ‘a’ partition.
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
The system maintains a list of currently mounted file systems. If no arguments
are given to mount
, this list is printed.
The options are as follows:
- Causes mount to try to mount
all of the file systems listed in the
except those for which the “noauto” or “net”
options are specified.
- 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.
- 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.
- 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.
- If used with either -A or
-a, mount will
only look at file systems which have the “net” option
specified. By default file systems with the “net” option are
- Options can be given with (or without) a ‘no’
prefix to invert their meaning. The options listed below specify
non-default values. For example, ‘nosoftdep’ is the default,
so ‘softdep’ can be used to mount the file system using soft
dependencies. Multiple options can be specified in a comma-separated list.
The available options are as follows:
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:
- Metadata I/O to the file system should be done
asynchronously. By default, only regular data is read/written
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
where it can give a factor of two speed increase.
The options async and
softdep are mutually exclusive.
- 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 atime.
- 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
- 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.
- (FFS only) Do not check permissions when creating,
accessing or modifying files and directories in the mounted file
system. This allows unprivileged users to construct a file hierarchy
containing special device nodes and files with arbitrary file mode,
owner or group without restriction. Only the owner, group and mode of
the root directory of the filesystem will be honored so access to the
filesystem can be locked down. The noperm option also enables the
nodev and noexec options to ensure that interpretation of the file
modes and special devices cannot be used to gain privileges.
- An alias for rdonly.
- Do not allow set-user-identifier or
set-group-identifier bits to take effect.
- The same as -r; mount the
file system read-only (even the superuser may not write it).
- An alias for rdonly.
- (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 is ignored when using the
-u flag and a file system is already
The options async and
softdep are mutually exclusive.
- Regular data I/O to the file system should be done
synchronously. By default, only metadata is read/written
- The same as -u; indicate
that the status of an already mounted file system should be
- Processes that ask for memory to be made writeable plus
executable using the
system calls are killed by default. This option allows those processes
to continue operation. It is typically used on the
That causes mount to execute the equivalent of:
# mount -t mfs -o rw,nodev,nosuid,-s=153600 /dev/sd0b /tmp
The equivalent example in
# /sbin/mount_mfs -o rw,nodev,nosuid -s 153600 /dev/sd0b /tmp
swap /tmp mfs rw,nodev,nosuid,-s=153600 0 0
- 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
- Skip mounting the file system if it is already mounted. See
the -a flag for a description of the criteria
used to decide if a file system is already mounted.
- 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:
mounts all file systems except those of type NFS and MFS .
mount will attempt to execute a program in
where XXX is replaced by the type name. For
example, NFS file systems are mounted by the program
- 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
- Verbose mode.
- 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
- file system table
Mount a CD-ROM on node /mnt/cdrom
# mount -t cd9660 -r /dev/cd0a
Mount an MS-DOS USB stick with DUID 3eb7f9da875cb9ee on node
# mount -t msdos 3eb7f9da875cb9ee.i
Graft a remote NFS file system on host host
, on node
# mount host:/path/name /mnt/nfs
with option “dev”:
# mount -u -o dev /var
command appeared in
Version 1 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).