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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 [-DLlMNSUX] [-a maxcontig] [-b block-size] [-c cylinders]
           [-d rotdelay] [-e maxbpg] [-F file] [-f frag-size] [-i bytes]
           [-m percent-free] [-n rotational-positions] [-O optimization]
           [-o mount-options] [-p permissions] [-s size] [-v version]
           [-w user:group] md-device mount-point
     mdmfs -C [-lNU] [-a maxcontig] [-b block-size] [-c cylinders]
           [-d rotdelay] [-e maxbpg] [-F file] [-f frag-size] [-i bytes]
           [-m percent-free] [-n rotational-positions] [-O optimization]
           [-o mount-options] [-s size] [-v version] 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 using
     newfs(8), and mounts it using mount(8).  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 oth-
     erwise specified with one of the options below, it uses the default argu-
     ments 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      Enable full compatibility mode with mount_mfs(8).  See the
             COMPATIBILITY section for more information.

     -c cylinders
             The number of cylinders 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 rotdelay
             Specify the minimum time in milliseconds required to initiate
             another disk transfer on the same cylinder.  Modern disks with
             read/write-behind achieve higher performance without this fea-
             ture, so it is best to leave it at 0 milliseconds.

     -e maxbpg
             Indicate the maximum number of blocks any single file can allo-
             cate out of a cylinder group before it is forced to begin allo-
             cating 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 rotational-positions
             The default number of rotational positions to distinguish.

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

     -U      Enable soft-updates on the file system.  This is the default,
             even in compatibility mode, and is accepted only for compatibil-
             ity.  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 specify-
             ing 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, respec-
     tively.  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.  See the pro-
     grams that the options are passed to for more information on their seman-

     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

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

     Full compatibility is enabled with the -C flag, or by starting mdmfs with
     the name mount_mfs or mfs (as returned by getprogname(3)).  In this mode,
     only the options which would be accepted by mount_mfs(8) are valid.  Fur-
     thermore, the following behavior, as done by mount_mfs(8), is duplicated:

           o   The file mode of mount-point is set 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 6.2                    February 26, 2004                   FreeBSD 6.2


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