MDMFS(8) BSD System Manager's Manual MDMFS(8)NAME
mdmfs, mount_mfs — configure and mount an in-memory file system using the
SYNOPSISmdmfs [-DLlMNPSUX] [-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] [-n rotational-positions] [-O optimization]
[-o mount-options] [-p permissions] [-s size] [-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 han‐
dle geom_uzip(4) compressed disk images, as long as the kernel supports
this GEOM class. All the command line options are passed to the appro‐
priate program at the appropriate stage in order to achieve the desired
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.
Specify the maximum number of contiguous blocks that will be laid
out before forcing a rotational delay (see the -d option).
The block size of the file system, in bytes.
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.
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.
Use path-mdconfig as a location of the mdconfig(8) utility.
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.
Create a vnode-backed (MD_VNODE) memory disk backed by file.
The fragment size of the file system in 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
-M Create a malloc(9) backed disk (MD_MALLOC) instead of a swap-
The percentage of space reserved for the superuser.
-N Do not actually run the helper programs. This is most useful in
conjunction with -X.
The default number of rotational positions to distinguish.
Select the optimization preference; valid choices are space and
time, which will optimize for minimum space fragmentation and
minimum time spent allocating blocks, respectively.
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
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.
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, and
is accepted only for compatibility. It is only really useful to
negate the -S flag, should such a need occur.
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
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
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/
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 compati‐
bility 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.
SEE ALSOmd(4), fstab(5), mdconfig(8), mount(8), newfs(8)AUTHORS
BSD February 15, 2007 BSD