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DESCRIPTION

When md-device is `auto', mdmfs uses tmpfs(5) if it is present in the kernel or can be loaded as a module, otherwise it falls back to using md(4) auto-unit as if `md' had been specified.

When md-device is `tmpfs', mdmfs mounts a tmpfs(5) filesystem, translating the -s size option, if present, into a `-o size=' mount option. Any -o options on the command line are passed through to the tmpfs(5) mount. Options specific to mdconfig(8) or newfs(8) are ignored.

When md-device does not result in tmpfs(5) being used, then an md(4) device is configured instead. By default, mdmfs creates a swap-based (MD_SWAP) disk with soft-updates enabled and mounts it on mount-point. It uses the md(4) device specified by md-device. If md-device is ‘md’ (no unit number), it will use md(4)'s auto-unit feature to automatically select an unused device. Unless otherwise specified with one of the options below, it uses the default arguments to all the helper programs.

The following options are available. Where possible, the option letter matches the one used by mount_mfs(8) for the same thing.

-a maxcontig

Specify the maximum number of contiguous blocks that will be laid out before forcing a rotational delay (see the -d option).

-b block-size

The block size of the file system, in bytes.

-c blocks-per-cylinder-group

The number of blocks per cylinder group in the file system.

-D

If not using auto-unit, do not run mdconfig(8) to try to detach the unit before attaching it.

-d max-extent-size

The file system may choose to store large files using extents. This parameter specifies the largest extent size that may be used. It is presently limited to its default value which is 16 times the file system blocksize.

-E path-mdconfig

Use path-mdconfig as a location of the mdconfig(8) utility.

-e maxbpg

Indicate the maximum number of blocks any single file can allocate out of a cylinder group before it is forced to begin allocating blocks from another cylinder group.

-F file

Create a vnode-backed (MD_VNODE) memory disk backed by file.

-f frag-size

The fragment size of the file system in bytes.

-i bytes

Number of bytes per inode.

-l

Enable multilabel MAC on the new file system.

-L

Show the output of the helper programs. By default, it is sent to /dev/null.

-M

Create a malloc(9) backed disk (MD_MALLOC) instead of a swap-backed disk.

-m percent-free

The percentage of space reserved for the superuser.

-N

Do not actually run the helper programs. This is most useful in conjunction with -X.

-n

Do not create a .snap directory on the new file system.

-O optimization

Select the optimization preference; valid choices are space and time, which will optimize for minimum space fragmentation and minimum time spent allocating blocks, respectively.

-o mount-options

Specify the mount options with which to mount the file system. See mount(8) for more information.

-P

Preserve the existing file system; do not run newfs(8). This only makes sense if -F is specified to create a vnode-backed disk.

-p permissions

Set the file (directory) permissions of the mount point mount-point to permissions. The permissions argument can be in any of the mode formats recognized by chmod(1). If symbolic permissions are specified, the operation characters “+” and “-” are interpreted relative to the initial permissions of “a=rwx”.

-S

Do not enable soft-updates on the file system.

-s size

Specify the size of the disk to create. This only makes sense if -F is not specified. That is, this will work when the backing storage is some form of memory, as opposed to a fixed-size file. The size may include the usual SI suffixes (k, m, g, t, p). A number without a suffix is interpreted as a count of 512-byte sectors.

-t

Turn on the TRIM enable flag for newfs(8). When used with a file system that issue BIO_DELETE bio requests, md(4) returns deleted blocks to the system memory pool.

-T fstype

Specify a file system type for a vnode-backed memory disk. Any file system supported by mount(8) command can be specified. This option only makes sense when -F and -P are used.

-U

Enable soft-updates on the file system. This is the default, and is accepted only for compatibility. It is only really useful to negate the -S flag, should such a need occur.

-v version

Specify the UFS version number for use on the file system; it may be either 1 or 2. The default is derived from the default of the newfs(8) command.

-w user:group

Set the owner and group to user and group, respectively. The arguments have the same semantics as with chown(8), but specifying just a user or just a group is not supported.

-X

Print what command will be run before running it, and other assorted debugging information.

The -F and -s options are passed to mdconfig(8) as -f and -s, respectively. The -a, -b, -c, -d, -e, -f, -i, -m and -n options are passed to newfs(8) with the same letter. The -O option is passed to newfs(8) as -o. The -o option is passed to mount(8) with the same letter. The -T option is passed to mount(8) as -t. For information on semantics, refer to the documentation of the programs that the options are passed to.