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MOUNT(8) System Manager's Manual MOUNT(8)

mount — mount file systems

mount [-adfrkuvw] [-t lfs | external_type]

mount [-dfrkuvw] special | mount_point

mount [-dfrkuvw] [-o options] [-t lfs | external_type] special mount_point

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:

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.
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.
Forces the revocation of write access when trying to downgrade a filesystem mount status from read-write to read-only.
In the course of the mount system call, the kernel should not follow any symlinks that may be present in the provided mount-on directory.

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 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).
nofollow
This option indicates that in the course of the mount system call, the kernel should not follow any symlinks that may be present in the provided mount-on directory. This is the same as the -k option.

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
Mount the file system read-only (even the super-user may not write it). The same as the “rdonly” argument to the -o option.
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 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.

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.
Verbose mode.
Mount the file system read-write.

The options specific to NFS filesystems are described in the mount_nfs(8) manual page.

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)

It is possible for a corrupted file system to cause a crash.

A mount command appeared in Version 6 AT&T UNIX.

June 16, 1994 BSD 4