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,
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, but this behaviour is
deprecated, and will be removed in a future version of
mount.
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.
-
-
- 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 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.
-
-
- 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:
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 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),
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_smbfs(8),
rump_sysvbfs(8),
rump_tmpfs(8),
rump_udf(8),
umount(8)
HISTORY
A
mount command appeared in
Version 1
AT&T UNIX.