Updated: 2022/Sep/29
Please read Privacy Policy. It's for your privacy.
MOUNT(8) System Manager's Manual MOUNT(8)
NAME
mount - mount file systems
SYNOPSIS
mount [-Aadfruvw] [-t type]
mount [-dfruvw] {special | node}
mount [-dfruvw] [-o options] [-t type] special node
DESCRIPTION
The mount command invokes a file system-specific program to prepare and
graft the special device on to the file system tree at the point node, or
to update options for an already-mounted file system.
These programs are named "mount_<fstype>" where "<fstype>" refers to the
file system-specific type; for example for NFS the mount program is
called mount_nfs(8).
The node argument is always interpreted as a directory in the name space
of currently mounted file systems. The special argument is interpreted
in different ways by the programs that handle different file system
types; for example, mount_ffs(8) interprets it as a device node,
mount_null(8) interprets it as a directory name, mount_nfs(8) interprets
it as reference to a remote host and a directory on that host, and
mount_tmpfs(8) ignores it.
The system maintains a list of currently mounted file systems. This list
is printed if mount is invoked with no arguments, and with no options
that require some other behaviour.
If exactly one of special or node is provided, then the missing
information (including the file system type) is taken from the fstab(5)
file. The provided argument is looked up first in the "fs_file", then in
the "fs_spec" column. If the matching entry in fstab(5) has the string
"from_mount" as its "fs_spec" field, the device or remote file system
already mounted at the location specified by "fs_spec" will be used.
If both special and node are provided, then fstab(5) is not used. In
this case, if the file system type is not specified via the -t flag, then
mount may determine the type from the disk label (see disklabel(8)). In
addition, if special contains a colon (`:') or at sign (`@'), then the
nfs type is inferred. In NetBSD, the file system mounting policy is
dictated by the running security models. The default security model may
allow unprivileged mounting; see secmodel_suser(9) and
secmodel_extensions(9) for details.
The options are as follows:
-A Causes mount to try to mount all of the file systems listed in
the fstab(5) file 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 Forces the revocation of write access when trying to downgrade a
file system 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. In the event of a crash, it is
impossible for the system to verify the integrity of
data on a file system mounted with this option. You
should only use this option if you have an
application-specific data recovery mechanism, or are
willing to recreate the file system from scratch.
noasync Clear async mode.
automounted
This flag indicates that the file system was mounted
by automountd(8). Automounted file systems are
automatically unmounted by autounmountd(8).
discard Use DISCARD/TRIM commands if disk and driver support
it.
EXPERIMENTAL - negatively influences filesystem
performance by increasing fragmentation, causes free
block map inconsistency on unclean shutdown, and is
incompatible with log. If log option is also used,
discard is automatically disabled.
extattr Enable extended attributes, if the filesystem
supports them and does not enable them by default.
Currently this is only the case for UFS1.
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.
getargs Retrieves the file system specific mount arguments
for the given mounted file system and prints them.
hidden By setting the MNT_IGNORE flag, causes the mount
point to be excluded from the list of file systems
shown by default with df(1).
noatime Never update the access time field for files. This
option is useful for optimizing read performance on
file systems, and avoiding excess writes on flash-
based file systems.
noauto This file system should be skipped when mount is run
with the -a flag.
nocoredump Do not allow programs to create crash dumps (core
files) on the file system. This option can be used
to help protect sensitive data by keeping core files
(which may contain sensitive data) from being created
on insecure file systems. Only core files that would
be created by program crashes are prevented by use of
this flag; the behavior of savecore(8) is not
affected.
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.
nodevmtime Do not update modification times on device special
files. This option is useful on laptops or other
systems that perform power management.
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 set-group-
identifier bits to take effect.
port (NFS only) Use the specified NFS port.
rdonly The same as -r; mount the file system read-only (even
the super-user may not write it).
reload Reload all incore data for a file system. This is
used mainly after running fsck(8) on the root file
system and finding things to fix. The file system
must be mounted read-only. All cached meta-data are
invalidated, superblock and summary information is
re-read from disk, all cached inactive vnodes and
file data are invalidated and all inode data are re-
read for all active vnodes.
rump Instead of running "mount_<fstype>" to mount the file
system, run "rump_<fstype>". This uses a userspace
server to mount the file system and does not require
kernel support for the specific file system type.
See the -t flag and respective rump_type manual page
for more information.
log (FFS only) Mount the file system with wapbl(4) meta-
data journaling, also known simply as logging. It
provides rapid metadata updates and eliminates the
need to check file system consistency after a system
outage. It requires the WAPBL option to be enabled
in the running kernel. See wapbl(4) for more
information. This option requires the "UFS2" (level
4) superblock layout, which is the default for newly
created FFSv1 and FFSv2 file systems. To update an
old file system with an earlier superblock format,
use the -c option of fsck_ffs(8).
log cannot be used together with discard.
A file system mounted with log can be mounted also
with async, but such filesystem behaves the same as
if async was not specified - meta-data writes use the
log, hence its integrity is still guaranteed.
symperm Recognize permission of symbolic link when reading or
traversing link.
sync All I/O to the file system should be done
synchronously. This is not equivalent to the normal
mode in which only metadata is written synchronously.
nosync Clear sync mode.
union Causes the namespace at the mount point to appear as
the union of the mounted file system root (referred
to as the upper layer), and the existing directory
(referred to as the lower layer). Name lookups will
be done in the upper layer first. If a name does not
exist in the upper layer, then the name will be
looked up in the lower layer. If a name exists in
both the upper and lower layers, then only the upper
instance is accessible. Creation of new files is
done in the upper layer, except in the case of the
fdesc file system (see mount_fdesc(8)).
Note that the union option can be applied to any type
of file system, and is fundamentally different from
mount_union(8), which is a particular type of file
system. Also note that the union option affects the
file system name space only at the mount point
itself; it does not apply recursively to
subdirectories.
update The same as -u; indicate that the status of an
already mounted file system should be changed.
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,-N,-s=32m swap /tmp
causes mount to execute the equivalent of:
/sbin/mount_mfs -o nosuid -N -s 32m swap /tmp
-r The file system is to be mounted read-only. 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 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. The set of options is determined by first extracting
the options for the file system from the fstab(5) file, then
applying any options specified by the -o argument, and finally
applying the -r or -w option.
-v Verbose mode. If this flag is specified more than once, then the
file system-specific mount arguments are printed for the given
mounted file system.
-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_<fstype>" commands; for
instance, the options specific to Berkeley Fast File System (FFS) are
described in the mount_ffs(8) manual page.
The particular type of file system in each partition of a disk can be
found by examining the disk label with the disklabel(8) command.
FILES
/etc/fstab file system table
EXAMPLES
Some useful examples:
CD-ROM mount -t cd9660 -r /dev/cd0a /cdrom
MS-DOS mount -t msdos /dev/fd0a /floppy
NFS mount -t nfs nfs-server-host:/directory/path /mount-point
MFS (32 megabyte)
mount -t mfs -o nosuid,-s=32m swap /tmp
The "noauto" directive in /etc/fstab can be used to make it easy to
manually mount and unmount removable media using just the mountpoint
filename, with an entry like this:
/dev/cd0a /cdrom cd9660 ro,noauto 0 0
That would allow a simple command like "mount /cdrom" or "umount /cdrom"
for media using the ISO-9660 file system format in the first CD-ROM
drive.
DIAGNOSTICS
The error "Operation not supported by device" indicates that the mount
for the specified file system type cannot be completed because the kernel
lacks support for the said file system. See options(4).
The error "Operation not permitted" may indicate that the mount options
include privileged options and/or do not include options that exclude
privileged options. One should try using at least "nodev" and "nosuid"
in such cases:
mount -t cd9660 -o nodev,nosuid /dev/cd0a /mnt
SEE ALSO
df(1), mount(2), options(4), wapbl(4), fstab(5), automount(8),
automountd(8), autounmountd(8), disklabel(8), fsck(8), mount_ados(8),
mount_cd9660(8), mount_chfs(8), mount_ext2fs(8), mount_fdesc(8),
mount_ffs(8), mount_filecore(8), mount_kernfs(8), mount_lfs(8),
mount_mfs(8), mount_msdos(8), mount_nfs(8), mount_ntfs(8), mount_null(8),
mount_overlay(8), mount_portal(8), mount_procfs(8), mount_tmpfs(8),
mount_udf(8), mount_umap(8), mount_union(8), rump_cd9660(8), rump_efs(8),
rump_ext2fs(8), rump_ffs(8), rump_hfs(8), rump_lfs(8), rump_msdos(8),
rump_nfs(8), rump_ntfs(8), rump_sysvbfs(8), rump_tmpfs(8), rump_udf(8),
umount(8)
HISTORY
A mount command appeared in Version 1 AT&T UNIX.
NetBSD 10.99 July 10, 2022 NetBSD 10.99