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.
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,
and
mount_nfs(8)
interprets it as reference to a remote host and a directory on that host.
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, but this behaviour is deprecated, and will be
removed in a future version of
.
In
NetBSD,
a file system can only be mounted by an ordinary user who owns the
point
node
and has access to the
special
device (at least read permissions).
Also, the
vfs.generic.usermount
sysctl(3)
must be set to 1 to permit file system mounting by ordinary users,
see
sysctl(8).
Finally, the flags
nosuid
and
nodev
must be given for non-superuser mounts.
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.
- 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
that are used as news spools.
- 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_type to mount the file system, run rump_type.
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.
- softdep
-
(FFS only) Mount the file system using soft dependencies.
This means that metadata will not be written immediately,
but 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 will be ignored when using the
-u
flag and a file system is already mounted read/write.
This option has gone through moderate to heavy testing,
but should still be used with care.
A file system mounted with
softdep
can not be mounted with
async
or
log.
It requires the
SOFTDEP
option to be enabled in the running kernel.
- log
-
(FFS only with UFS2 superblock layout)
Mount the file system with
wapbl(4)
meta-data journaling.
It provides rapid file system consistency checking after a system outage.
It also provides better general-use performance over regular FFS similar to
softdep.
This option has gone through moderate testing, but still should be considered
experimental.
A file system mounted with
log
can not be mounted with
async
or
softdep.
It requires the
WAPBL
option to be enabled in the running kernel.
See
wapbl(4)
for more information.
- 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 and the existing directory.
Lookups will be done in the mounted file system first.
If those operations fail due to a non-existent file the underlying
directory is then accessed.
All creates are done in the mounted file system, except for the fdesc
file system.
- 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_XXX
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
don't 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),
disklabel(8),
fsck(8),
mount_ados(8),
mount_cd9660(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 6 AT&T UNIX
.