Command Section
MDMFS(8)                FreeBSD System Manager's Manual               MDMFS(8)

     mdmfs, mount_mfs - configure and mount an in-memory file system using the
     md(4) driver

     mdmfs [-DLlMNnPStTUX] [-a maxcontig] [-b block-size]
           [-c blocks-per-cylinder-group] [-d max-extent-size]
           [-E path-mdconfig] [-e maxbpg] [-F file] [-f frag-size] [-i bytes]
           [-m percent-free] [-O optimization] [-o mount-options]
           [-p permissions] [-s size] [-T fstype] [-v version] [-w user:group]
           md-device mount-point

     The mdmfs utility is designed to be a work-alike and look-alike of the
     deprecated mount_mfs(8).  The end result is essentially the same, but is
     accomplished in a completely different way.  The mdmfs utility configures
     an md(4) disk using mdconfig(8), puts a UFS file system on it (unless -P
     was specified) using newfs(8), and mounts it using mount(8).  It can
     handle geom_uzip(4) compressed disk images, as long as the kernel
     supports this GEOM class.  All the command line options are passed to the
     appropriate program at the appropriate stage in order to achieve the
     desired effect.

     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

     -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

     -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 for the default
             swap-backed (MD_SWAP) disks, and the optional (-M) malloc(9)
             backed disks (MD_MALLOC).

     -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.  See the programs
     that the options are passed to for more information on their semantics.

     Create and mount a 32 megabyte swap-backed file system on /tmp:

           mdmfs -s 32m md /tmp

     The same file system created as an entry in /etc/fstab:

           md /tmp mfs rw,-s32m 2 0

     Create and mount a 16 megabyte malloc-backed file system on /tmp using
     the /dev/md1 device; furthermore, do not use soft-updates on it and mount
     it async:

           mdmfs -M -S -o async -s 16m md1 /tmp

     Create and mount a geom_uzip(4) based compressed disk image:

           mdmfs -P -F foo.uzip -oro md.uzip /tmp/

     Mount the same image, specifying the /dev/md1 device:

           mdmfs -P -F foo.uzip -oro md1.uzip /tmp/

     Configure a vnode-backed file system and mount its first partition, using
     automatic device numbering:

           mdmfs -P -F foo.img mds1a /tmp/

     Mount a vnode-backed cd9660 file system using automatic device numbering:

           mdmfs -T cd9660 -P -F foo.iso md /tmp

     The mdmfs utility, while designed to be compatible with mount_mfs(8), can
     be useful by itself.  Since mount_mfs(8) had some silly defaults, a
     ``compatibility'' mode is provided for the case where bug-to-bug
     compatibility is desired.

     Compatibility is enabled by starting mdmfs with the name mount_mfs or mfs
     (as returned by getprogname(3)).  In this mode, the following behavior,
     as done by mount_mfs(8), is duplicated:

              The file mode of mount-point is set by default to 01777 as if
               -p 1777 was given on the command line.

     md(4), fstab(5), mdconfig(8), mount(8), newfs(8)

     Dima Dorfman

FreeBSD 11.1-RELEASE-p4          March 9, 2016         FreeBSD 11.1-RELEASE-p4
Command Section