MOUNT(8) BSD System Manager's Manual MOUNT(8)
mount - mount filesystems
mount [-Aadfruvw] [-t type]
mount [-dfruvw] special | node
mount [-dfruvw] [-o options] [-t type] special node
The mount command invokes a filesystem specific program to prepare and
graft the special device or remote node (rhost:path) on to the filesystem
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 filesystems. If no argu-
ments 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 filesystems 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 filesystems 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 filesystem (other than
the root filesystem) appears to be already mounted, mount will
not try to mount it again. mount assumes that a filesystem is al-
ready mounted if a filesystem with the same type is mounted on
the given mount point. More stringent checks are not possible be-
cause some filesystem 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
filesystem 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 filesystems 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 can be given with (or without) a 'no' prefix to invert
their meaning. The options listed below specify non-default
values. For example, 'noasync' is the default, so 'async' can be
used to mount a filesystem asynchronously. Multiple options can
be specified in a comma-separated list. The available options are
as follows:
async All I/O to the filesystem should be done asynchronously.
This is a dangerous flag to set since it does not guaran-
tee to keep a consistent filesystem structure on the
disk. You should not use this flag unless you are
prepared to recreate the filesystem 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 in-
crease.
softdep
(FFS only.) Mount the filesystem using soft dependencies.
Instead of metadata being written immediately, it is
written in an ordered fashion to keep the on-disk state
of the filesystem consistent. This results in significant
speedups for file create/delete operations. This option
will be ignored when using the -u flag and a filesystem
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 filesystem 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.
noauto Do not mount the filesystem automatically (either at boot
or with the -A or -a options).
nodev Do not interpret character or block special devices on
the filesystem. This option is useful for a server that
has filesystems containing special devices for architec-
tures other than its own.
noexec Do not allow execution of any binaries on the mounted
filesystem. This option is useful for a server that has
filesystems containing binaries for architectures other
than its own.
nosuid Do not allow set-user-identifier or set-group-identifier
bits to take effect.
rdonly The same as -r; mount the filesystem read-only (even the
superuser may not write it).
sync All I/O to the filesystem should be done synchronously.
update The same as -u; indicate that the status of an already
mounted filesystem should be changed.
Any additional options specific to a given filesystem type (see
the -t option) may be passed as a comma separated list; these op-
tions 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 filesystem is to be mounted read-only. Mount the filesystem
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 filesystem
type. The type ffs is the default. 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 com-
ma 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,mfs
mounts all filesystems 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 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 filesystem 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 speci-
fied. Only options specified on the command line with -o are
changed; other filesystem options are unaltered. The options set
in the fstab(5) table are ignored.
-v Verbose mode.
-w The filesystem object is to be read and write.
The options specific to the various filesystem types are described in the
manual pages for those filesystems' mount_XXX commands. For instance, the
options specific to Berkeley Fast Filesystems are described in the
mount_ffs(8) manual page.
/etc/fstab filesystem table
Mount a CD-ROM on node /mnt/cdrom:
# mount -t cd9660 -r /dev/cd0a /mnt/cdrom
Mount an MS-DOS floppy on node /mnt/floppy:
# mount -t msdos /dev/fd0a /mnt/floppy
Graft a remote NFS filesystem on host host, path /path/name, on node
/mnt/nfs:
# mount host:/path/name /mnt/nfs
Remount /var with option "dev":
# mount -u -o dev /var
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_portal(8), mount_procfs(8), mount_udf(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 filesystem. 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).
MirBSD #10-current March 27, 1994 3