mdmfs, mount_mfs -- configure and mount an in-memory file system using
the md(4) driver
mdmfs [-DLMNSUX] [-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 [-NU] [-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 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 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 feature,
so it is best to leave it at 0 milliseconds.
-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 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 swapbacked
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 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 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 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. 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
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. Furthermore,
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 5.2.1 August 5, 2001 FreeBSD 5.2.1 [ Back ] |
