mount
MOUNT(8) System Manager's Manual MOUNT(8)
NAME
mount – mount file systems
SYNOPSIS
mount [-adfruvw] [-t lfs | external_type]
mount [-dfruvw] special | mount_point
mount [-dfruvw] [-o options] [-t lfs | external_type] special mount_point
DESCRIPTION
The mount command calls the mount(2) system call to prepare and graft a
special device or the remote node (rhost:path) on to the file system tree
at the point mount_point, which must be a directory. If either special or
mount_point are not provided, the appropriate information is obtained via
the getfsent(3) library routines.
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:
-a All the filesystems listed via getfsent(3) are mounted. Exceptions
are those marked as ``noauto;'' excluded by the -t flag (see
below); entries that are neither ``ro,'' ``rw,'' or ``rq;'' ``nfs''
entries that also have ``net'' as an option; and already-mounted
``nfs'' entries.
-d Causes everything to be done except for the actual system call.
This option is useful in conjunction with the -v flag to determine
what the mount command is trying to do.
-f Forces the revocation of write access when trying to downgrade a
filesystem mount status from read-write to read-only.
-o Options are specified with a -o flag followed by a comma separated
string of options. The following options are available:
async All I/O to the file system should be done asynchronously.
This can be somewhat dangerous with respect to losing data
when faced with system crashes and power outages. This is
also the default. It can be avoided with the noasync
option.
force The same as -f; forces the revocation of write access when
trying to downgrade a filesystem mount status from read-
write to read-only.
noasync
This filesystem should not force all I/O to be written
asynchronously.
noauto This filesystem should be skipped when mount is run with
the -a flag.
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.
noowners
Ignore the ownership field for the entire volume. This
causes all objects to appear as owned by user ID 99 and
group ID 99. User ID 99 is interpreted as the current
effective user ID, while group ID 99 is used directly and
translates to ``unknown''.
nosuid Do not allow set-user-identifier or set-group-identifier
bits to take effect.
rdonly The same as -r; mount the file system read-only (even the
super-user 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 to appear as the union of directories
of the mounted filesystem with corresponding directories in
the underlying filesystem. 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.
noatime
Do not update the file access time when reading from a
file. This option is useful on file systems where there
are large numbers of files and performance is more critical
than updating the file access time (which is rarely ever
important).
strictatime
Always update the file access time when reading from a
file. Without this option the filesystem may default to a
less strict update mode, where some access time updates are
skipped for performance reasons. This option could be
ignored if it is not supported by the filesystem.
nobrowse
This option indicates that the mount point should not be
visible via the GUI (i.e., appear on the Desktop as a
separate volume).
Any additional options specific to a filesystem type that is not
one of the internally known types (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 hfs -o nosuid,-w,-m=755 /dev/disk2s9 /tmp
causes mount to execute the equivalent of:
/sbin/mount_hfs -o nosuid -w -m 755 /dev/disk2s9 /tmp
-r Mount the file system read-only (even the super-user may not write
it). The same as the “rdonly” argument to the -o option.
-t lfs | external type
The argument following the -t is used to indicate the file system
type. There is no default local file system for use with mount. A
type must be specified in order to mount a non-NFS filesystem. The
-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 “no” to specify the filesystem types for
which action should not be taken. For example, the mount command:
mount -a -t nonfs,hfs
mounts all filesystems except those of type NFS and HFS.
If the type is not one of the internally known types, mount will
attempt to execute a program in /sbin/mount_XXX where XXX is
replaced by the type name. For example, nfs filesystems 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 filesystem
are currently open for writing unless the -f flag is also
specified. The set of options is determined by first extracting
the options for the file system from the filesystem table (see
getfsent(3)) then applying any options specified by the -o
argument, and finally applying the -r or -w option.
-v Verbose mode.
-w Mount the file system read-write.
The options specific to NFS filesystems are described in the
mount_nfs(8) manual page.
SEE ALSO
mount(2), getfsent(3), mount_afp(8), mount_cd9660(8), mount_cddafs(8),
mount_fdesc(8), mount_hfs(8), mount_apfs(8), mount_msdos(8), mount_nfs(8),
mount_smbfs(8), mount_udf(8), mount_webdav(8), umount(8)
BUGS
It is possible for a corrupted file system to cause a crash.
HISTORY
A mount command appeared in Version 6 AT&T UNIX.
BSD 4 June 16, 1994 BSD 4