path: root/sbin/mdmfs/mdmfs.8

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.\" Copyright (c) 2001 Dima Dorfman <dd@FreeBSD.org>
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.Dd May 26, 2001
.Dt MDMFS 8
.Os
.Sh NAME
.Nm mdmfs
.Nd configure and mount an in-memory filesystem using the
.Xr md 4
driver
.Sh SYNOPSIS
.Nm
.Op Fl DLMNSX
.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 w Ar user : Ns Ar group
.Ar md-device
.Ar mount-point
.Sh DESCRIPTION
The
.Nm
program 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.
.Nm
configures an
.Xr md 4
disk using
.Xr mdconfig 8 ,
labels it using
.Xr disklabel 8 ,
puts a UFS filesystem 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 filesystem, in bytes.
.It Fl c Ar cylinders
The number of cylinders per cylinder group in the filesystem.
.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 filesystem 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 filesystem.
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 filesystem.
.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 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.
.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 filesystem on
.Pa /tmp :
.Pp
.Dl "mdmfs -s 32m md /tmp"
.Pp
Create and mount a 16 megabyte malloc-backed filesystem on
.Pa /tmp
using the
.Pa /dev/md1
device;
furthermore,
do not use soft-updates it and mount it
.Cm async :
.Pp
.Dl "mdmfs -M -S -o async -s 16m md1 /tmp"
.Sh SEE ALSO
.Xr md 4 ,
.Xr disklabel 8 ,
.Xr mdconfig 8 ,
.Xr mount 8 ,
.Xr newfs 8
.Sh AUTHORS
.An Dima Dorfman
.Aq dd@FreeBSD.org