freebsd/sbin/mdmfs/mdmfs.8

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.\" Copyright (c) 2001 Dima Dorfman.
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.Dd August 5, 2001
.Dt MDMFS 8
.Os
.Sh NAME
.Nm mdmfs
.Nd configure and mount an in-memory file system using the
.Xr md 4
driver
.Sh SYNOPSIS
.Nm
.Op Fl DLMNSUX
.Op Fl a Ar maxcontig
.Op Fl b Ar block-size
.Op Fl c Ar cylinders
.Op Fl d Ar rotdelay
.Op Fl e Ar maxbpg
.Op Fl F Ar file
.Op Fl f Ar frag-size
.Op Fl i Ar bytes
.Op Fl m Ar percent-free
.Op Fl n Ar rotational-positions
.Op Fl O Ar optimization
.Op Fl o Ar mount-options
.Op Fl p Ar permissions
.Op Fl s Ar size
.Op Fl v Ar version
.Op Fl w Ar user : Ns Ar group
.Ar md-device
.Ar mount-point
.Nm
.Fl C
.Op Fl NU
.Op Fl a Ar maxcontig
.Op Fl b Ar block-size
.Op Fl c Ar cylinders
.Op Fl d Ar rotdelay
.Op Fl e Ar maxbpg
.Op Fl F Ar file
.Op Fl f Ar frag-size
.Op Fl i Ar bytes
.Op Fl m Ar percent-free
.Op Fl n Ar rotational-positions
.Op Fl O Ar optimization
.Op Fl o Ar mount-options
.Op Fl s Ar size
.Op Fl v Ar version
.Ar md-device
.Ar mount-point
.Sh DESCRIPTION
The
.Nm
utility is designed to be a work-alike and look-alike of the deprecated
.Xr mount_mfs 8 .
The end result is essentially the same,
but is accomplished in a completely different way.
The
.Nm
utility configures an
.Xr md 4
disk using
.Xr mdconfig 8 ,
puts a UFS file system on it using
.Xr newfs 8 ,
and mounts it using
.Xr mount 8 .
All the command line options are passed to the appropriate program
at the appropriate stage in order to achieve the desired effect.
.Pp
By default,
.Nm
creates a swap-based
.Pq Dv MD_SWAP
disk with soft-updates enabled
and mounts it on
.Ar mount-point .
It uses the
.Xr md 4
device specified by
.Ar md-device .
If
.Ar md-device
is
.Ql md
(no unit number),
it will use
.Xr md 4 Ns '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.
.Pp
The following options are available.
Where possible,
the option letter matches the one used by
.Xr mount_mfs 8
for the same thing.
.Bl -tag -width indent
.It Fl a Ar maxcontig
Specify the maximum number of contiguous blocks that will be laid
out before forcing a rotational delay
(see the
.Fl d
option).
.It Fl b Ar block-size
The block size of the file system, in bytes.
.It Fl C
Enable full compatibility mode with
.Xr mount_mfs 8 .
See the
.Sx COMPATIBILITY
section for more information.
.It Fl c Ar cylinders
The number of cylinders per cylinder group in the file system.
.It Fl D
If not using auto-unit,
do not run
.Xr mdconfig 8
to try to detach the unit before attaching it.
.It Fl d Ar rotdelay
Specify the mininum 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.
.It Fl e Ar 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.
.It Fl F Ar file
Create a vnode-backed
.Pq Dv MD_VNODE
memory disk backed by
.Ar file .
.It Fl f Ar frag-size
The fragment size of the file system in bytes.
.It Fl i Ar bytes
Number of bytes per inode.
.It Fl L
Show the output of the helper programs.
By default,
it is sent to
.Pa /dev/null .
.It Fl M
Create a
.Xr malloc 9
backed disk
.Pq Dv MD_MALLOC
instead of a swap-backed disk.
.It Fl m Ar percent-free
The percentage of space reserved for the superuser.
.It Fl N
Do not actually run the helper programs.
This is most useful in conjunction with
.Fl X .
.It Fl n Ar rotational-positions
The default number of rotational positions to distinguish.
.It Fl O Ar optimization
Select the optimization preference;
valid choices are
.Cm space
and
.Cm time ,
which will optimize for minimum space fragmentation and
minimum time spent allocating blocks,
respectively.
.It Fl o Ar mount-options
Specify the mount options with which to mount the file system.
See
.Xr mount 8
for more information.
.It Fl p Ar permissions
Set the file (directory) permissions of the mount point
.Ar mount-point
to
.Ar permissions .
.It Fl S
Do not enable soft-updates on the file system.
.It Fl s Ar size
Specify the size of the disk to create.
This only makes sense if
.Fl F
is
.Em not
specified.
That is,
this will work for the default swap-backed
.Pq Dv MD_SWAP
disks,
and the optional
.Pq Fl M
.Xr malloc 9
backed disks
.Pq Dv MD_MALLOC .
.It Fl 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
.Fl S
flag, should such a need occur.
.It Fl v Ar version
Specify the UFS version number for use on the file system; it may be
either
.Dv 1
or
.Dv 2 .
The default is derived from the default of the
.Xr newfs 8
command.
.It Fl w Ar user : Ns Ar group
Set the owner and group to
.Ar user
and
.Ar group ,
respectively.
The arguments have the same semantics as with
.Xr chown 8 ,
but specifying just a
.Ar user
or just a
.Ar group
is not supported.
.It Fl X
Print what command will be run before running it, and
other assorted debugging information.
.El
.Pp
The
.Fl F
and
.Fl s
options are passed to
.Xr mdconfig 8
as
.Fl f
and
.Fl s ,
respectively.
The
.Fl a , b , c , d , e , f , i , m
and
.Fl n
options are passed to
.Xr newfs 8
with the same letter;
the
.Fl O
option is passed to
.Xr newfs 8
as
.Fl o .
The
.Fl o
option is passed to
.Xr mount 8
with the same letter.
See the programs that the options are passed to for more information
on their semantics.
.Sh EXAMPLES
Create and mount a 32 megabyte swap-backed file system on
.Pa /tmp :
.Pp
.Dl "mdmfs -s 32m md /tmp"
.Pp
Create and mount a 16 megabyte malloc-backed file system on
.Pa /tmp
using the
.Pa /dev/md1
device;
furthermore,
do not use soft-updates on it and mount it
.Cm async :
.Pp
.Dl "mdmfs -M -S -o async -s 16m md1 /tmp"
.Sh COMPATIBILITY
The
.Nm
utility, while designed to be fully compatible with
.Xr mount_mfs 8 ,
can be useful by itself.
Since
.Xr mount_mfs 8
has some silly defaults, a
.Dq full compatibility
mode is provided for the case where bug-to-bug compatibility is desired.
.Pp
Full compatibility is enabled with the
.Fl C
flag,
or by starting
.Nm
with the name
.Li mount_mfs
or
.Li mfs
(as returned by
.Xr getprogname 3 ) .
In this mode, only the options which would be accepted by
.Xr mount_mfs 8
are valid.
Furthermore, the following behavior, as done by
.Xr mount_mfs 8 ,
is duplicated:
.Bl -bullet -offset indent
.It
The file mode of
.Ar mount-point
is set to
.Li 01777
as if
.Fl p Ar 1777
was given on the command line.
.El
.Sh SEE ALSO
.Xr md 4 ,
.Xr fstab 5 ,
.Xr mdconfig 8 ,
.Xr mount 8 ,
.Xr newfs 8
.Sh AUTHORS
.An Dima Dorfman