Geom question

Fri Oct 2 22:00:52 UTC 2015

On Fri, 2 Oct 2015 17:31:01 -0400, Chad J. Milios wrote:
> On 10/2/2015 5:00 PM, William A. Mahaffey III wrote:
> > On 10/02/15 15:31, Chad J. Milios wrote:
> >>> On Oct 2, 2015, at 3:41 PM, William A. Mahaffey III <wam at hiwaay.net> 
> >>> wrote:
> >>>
> >>> I am prepping to provision 2 boxen w/ FreeBSD 9.3R, preferably from 
> >>> a thumb drive. I would like to add a 'utils' directory w/ some 
> >>> scripts I wrote to automate the partitioning/slicing of the HDD's 
> >>> (2X on 1 box, 8X on the other), & also accumulate output from the 
> >>> install process in case questions arise. To that end, I am planning 
> >>> on partitioning/slicing a thumb drive, prepping it to be bootable 
> >>> following examples on the gpart man page, & copying verbatim stuff 
> >>> from the memstick.img for 9.3R that I downloaded a while back, as 
> >>> well as adding my utils directory. Reading up on gpart & geom raises 
> >>> 1 question: can I do all these preps on a disk image file I create 
> >>> w/ dd, or do i do them in place on the target memstick, then dd the 
> >>> results onto an on-disk image for safekeeping ? Put another way, can 
> >>> a disk image created by dd be a 'geom' for gpart ? TIA & have a good 
> >>> one.
> >>>
> >>> -- 
> >>>
> >>>     William A. Mahaffey III
> >> In a way, yes. `mdconfig -f filename` will make your file accessible 
> >> as a virtual device.
> >>
> >
> > Thanks for the info. I proceeded w/ trying to setup /dev/md0 as a 
> > bootable disk image as follows:
> >
> > [root at kabini1, /etc, 3:54:31pm] 758 % dd if=/dev/zero 
> > of=/home/memstick.img count=3699 bs=1m
> > 3699+0 records in
> > 3699+0 records out
> > 3878682624 bytes transferred in 8.324621 secs (465929036 bytes/sec)
> FYI, check out `man truncate` next time to save some time/space. Most 
> file systems support what are known as "sparse" files. That dd command 
> works just fine for this though.
> > [root at kabini1, /etc, 3:55:23pm] 759 % cat 
> > ~wam/FreeBSD/9.3/README.createBootableMBR-SD.txt
> >
> >      MBR:   Master Boot Record is used on PCs and removable media. 
> > Requires
> >             the GEOM_PART_MBR kernel option.  The GEOM_PART_EBR option 
> > adds
> >             support for the Extended Boot Record (EBR), which is used to
> >             define a logical partition.  The GEOM_PART_EBR_COMPAT option
> >             enables backward compatibility for partition names in the EBR
> >             scheme.  It also prevents any type of actions on such 
> > partitions.
> >
> >      Create an MBR scheme on ada0, then create a 30GB-sized FreeBSD 
> > slice, mark it active and install the boot0 boot manager:
> >
> >            /sbin/gpart create -s MBR ada0
> >            /sbin/gpart add -t freebsd -s 30G ada0
> >            /sbin/gpart set -a active -i 1 ada0
> >            /sbin/gpart bootcode -b /boot/boot0 ada0
> >
> >      Now create a BSD scheme (BSD label) with space for up to 20 
> > partitions:
> >
> >            /sbin/gpart create -s BSD -n 20 ada0s1
> >
> >      Create a 1GB-sized UFS partition and a 4GB-sized swap partition:
> >
> >            /sbin/gpart add -t freebsd-ufs -s 1G ada0s1
> >            /sbin/gpart add -t freebsd-swap -s 4G ada0s1
> >
> >      Install bootstrap code for the BSD label:
> >
> >            /sbin/gpart bootcode -b /boot/boot ada0s1
> >
> > [root at kabini1, /etc, 3:55:50pm] 760 % mdconfig -f /home/memstick.img
> > md0
> > [root at kabini1, /etc, 3:56:26pm] 761 % /sbin/gpart create -s MBR md0
> > md0 created
> > [root at kabini1, /etc, 3:58:45pm] 762 % /sbin/gpart add -t freebsd -s 
> > 3698M md0
> > md0s1 added
> If you leave off the -s $SIZE option gpart will simply use up every 
> available byte for you
> > [root at kabini1, /etc, 3:59:14pm] 763 % /sbin/gpart set -a active -i 1 md0
> > active set on md0s1
> > [root at kabini1, /etc, 3:59:25pm] 764 % /sbin/gpart bootcode -b 
> > /boot/boot0 md0
> > bootcode written to md0
> > [root at kabini1, /etc, 3:59:44pm] 765 % /sbin/gpart create -s BSD md0s1
> > md0s1 created
> > [root at kabini1, /etc, 3:59:57pm] 766 % /sbin/gpart add -t freebsd-ufs 
> > md0s1
> > md0s1a added
> > [root at kabini1, /etc, DING!] 767 % /sbin/gpart bootcode -b /boot/boot 
> > md0s1
> > bootcode written to md0s1
> > [root at kabini1, /etc, 4:00:25pm] 768 % lltr /dev/md0*; date
> > crw-r-----  1 root  operator  0xd2 Oct  2 15:56 /dev/md0
> > crw-r-----  1 root  operator  0xd5 Oct  2 15:59 /dev/md0s1
> > crw-r-----  1 root  operator  0xd6 Oct  2 16:00 /dev/md0s1a
> > Fri Oct  2 16:00:44 MCDT 2015
> > [root at kabini1, /etc, 4:00:44pm] 769 % mount /dev/md0s1  /media/sd/
> > mount: /dev/md0s1: Invalid argument
> > [root at kabini1, /etc, 4:01:16pm] 770 % mount -t ufs /dev/md0s1 /media/sd/
> > mount: /dev/md0s1: Invalid argument
> > [root at kabini1, /etc, 4:01:34pm] 771 % mount -t ufs /dev/md0s1a /media/sd/
> > mount: /dev/md0s1a: Invalid argument
> > [root at kabini1, /etc, 4:01:41pm] 772 %
> >
> > & I appear to be stuck trying to mount the /dev/md0 device so I can 
> > copy stuff to it :-/. Any clues appreciated. TIA & have a good one.
> 
> you need to `newfs /dev/md0s1a` first before attempting to mount it, as 
> `gpart add -t freebsd-ufs $GEOM` only marks the meta info in the 
> outerlying structure (the front few blocks of /dev/md0s1 in your case) 
> and doesn't actually do what you're expecting.

Also consider using GPT instead of MBR for partitioning. The
corresponding virtial node would then be /dev/md0p1. See one
of my previous messages for examples dealing with md's.

> `man newfs` to decide 
> that you probably want the -U flag with that and might want the -J flag 
> as well.

If you intend to prepare SSDs or USB thumb drives, there are
some more options that can be tweaked (-m, -t, -i, maybe -L),
as well as mount options when the whole thing is running.

-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...