Re: /etc/rc.d/ramdisk script for review

Wes Peters wrote:

>A question came up on the mimedefang-users mailing list today.  One 
>user who has recently converted from 4.8 to 5.2.1 was lamenting the 
>fact there is no way to control ownership and permission of memory 
>disks in 5.x.  The MIMEdefang spool area, often placed on a ramdisk 
>for speed, needs to be owned by the MIMEdefang user and group.
>
>I poked around at mdmfs, aka mount_mfs, and thought there should be 
>a more 5.x-ish way to create ramdisks early enough in the boot process 
>to just put them in /etc/fstab directly.  Here's what I came up with.
>  
>
I like the notion of having rc.conf nobs to do this stuff with, but we 
can already use /etc/fstab to configure a ramdisk as such:

md                             /tmp           mfs                     
rw,-s3m         0               0
md                             /var            mfs                     
rw,-s7m         0               0

That is how I engineered wifibsd prior to the changes Brooks did to the 
diskless script of Matt's. It would seem to me that we
could have the ownership options next to the "rw,-s7m" options fields 
which already exists. Something like "rw,-s7m,-Owes:staff", or similare.

Since mount_md, or mdmfs, or whatever mount uses to do the task, could 
be changed to facilitate that one needful thing or using chown/chgrp, 
right?


>This is configured from /etc/rc.conf, as in:
>
>ramdisk_units="10 11 12"
>ramdisk_10_config="-t swap -s 128m"
>ramdisk_10_owner="wes:staff"
>ramdisk_10_perms="1755"
>ramdisk_11_config="-t malloc -s 32m"
>ramdisk_11_newfs="-b 4096 -f 1024"
>
>This results in /dev/md10 (with ownership and permissions as specified) 
>and /dev/md11 (with default ownership and permissions, 4K/1K block/frag
>size), but not a /dev/md12 as its type has not been specified.
>
>Here is the script:
>
>---- ramdisk
>
>#!/bin/sh -
>#
># Copyright (c) 2004  The FreeBSD Project
># All rights reserved.
>#
># Redistribution and use in source and binary forms, with or without
># modification, are permitted provided that the following conditions
># are met:
># 1. Redistributions of source code must retain the above copyright
>#    notice, this list of conditions and the following disclaimer.
># 2. Redistributions in binary form must reproduce the above copyright
>#    notice, this list of conditions and the following disclaimer in the
>#    documentation and/or other materials provided with the distribution.
>#
># THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
># ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
># IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
># ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
># FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
># DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
># OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
># HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
># LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
># OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
># SUCH DAMAGE.
>#
># $FreeBSD$
>#
>
># PROVIDE: ramdisk
># REQUIRE: localswap
># BEFORE: mountcritlocal
># KEYWORD: FreeBSD
>
>. /etc/rc.subr
>
>name="ramdisk"
>stop_cmd="ramdisk_stop"
>start_cmd="ramdisk_start"
>
>ramdisk_start()
>{
>	for unit in $ramdisk_units
>	do
>		eval mdoptions=\$ramdisk_${unit}_config
>		if [ "$mdoptions" = "${mdoptions##-t}" ]
>		then
>			echo "Type not specified for md$unit"
>			continue
>		fi
>		eval fsoptions=\$ramdisk_${unit}_newfs
>		eval owner=\$ramdisk_${unit}_owner
>		eval perms=\$ramdisk_${unit}_perms
>
>		echo Configuring ramdisk /dev/md$unit
>
>		mdconfig -a $mdoptions -u $unit
>		newfs $fsoptions /dev/md$unit
>		[ "X$owner" != "X" ] && chown $owner /dev/md$unit
>		[ "X$perms" != "X" ] && chmod $perms /dev/md$unit
>	done
>}
>
>ramdisk_stop()
>{
>	for unit in $ramdisk_units
>	do
>		if [ -c /dev/md$unit ] ; then
>			umount -f /dev/md$unit > /dev/null 2>&1
>			mdconfig -d -u $unit
>			echo Recovered ramdisk /dev/md$unit
>		fi
>	done
>}
>
>load_rc_config $name
>run_rc_command "$1"
>
>---- ramdisk
>  
>
Brooks already has something like this in rc.subr, we could just alter 
that, right?
I mean there is no need for duplication of the same task, right? Just 
need the chown parts.


>Gordon Tetlow suggested creating a mount_md program instead, which 
>would probably be a hackup of mdmfs.  To some extent, just linking
>/sbin/mount_md to /sbin/mdmfs would allow all of the options in mdmfs
>to be used in /etc/fstab.  Does anyone have strong preferences for 
>one approach vs. the other?
>  
>

I belive both methods have their place, and they do not have to be 
mutually exlusive.

-Jon Disnard (aka masta)
masta_at_wifibsd.org
diz_at_linuxpowered.com
http://www.wifibsd.org