FreeBSD 7.0 fdisk issue during installation

[Jonatan Evald Buus]

Thank you both for the very detailed description.
It's nice to get my suspicion about boot sequencing confirmed :-)

When I installed the system yesterday (I think I'll try a re-install today
based on your input) I observed however that all the slices I made appeared
to be bootable.
As originally mentioned I managed to get the system to boot when I only had
4 slices which resulted in the system only wanting to boot through the
FreeBSD Boot Manager. The Boot menu listed 4 menu items, each called
"FreeBSD".
If I only used the MBR to boot however, then the machine would fail with
"Invalid Partition Table" during startup.

I'm quite confident that I had only specified a single slice (/) as being
bootable through fdisk in sysinstall but apparently all 4 of them were made
bootable anyway.
I took a picture of my fdisk screen which can be found at
http://demo.ois-inc.com/freebsd_fdisk.jpg
>From the picture it appears (to me anyway) that only the first slice should
be bootable as indicated by the "A" flag?

Not sure what to make of this observation as you both indicate that I
wouldn't have had these problems if I only had made 1 slice bootable.
Does sysinstall make all slices bootable automatically?

Appreciate any input you may have to this observation.

/Jona

On Fri, Nov 21, 2008 at 11:58 PM, Jerry McAllister <jerrymc at msu.edu> wrote:

> On Fri, Nov 21, 2008 at 10:41:07PM +0100, Jonatan Evald Buus wrote:
>
> > Hi Jerry,
> > Thank you for the swift and very thorough response.
> >
> > If I understand you correctly, then I should only create 1 slice of the
> > entire disk (seeing as FreeBSD will be the only OS) using fdisk and then
> > partition the slice using bsdlabels from sysinstall?
>
> Yes.   Or you don't have to use sysinstall.  You can do it
> manually.   But, using sysinstall makes it easy.
>
> You don't absolutely have to slice or bsdlabel it.
> You can either just newfs the device /dev/da0 or you can create a slice
> and just newfs that /dev/da0s1.   Then you get that 'dangerously dedicated'
> disk which FreeBSD can use, but nothing else can including some non-FreeBSD
> boot managers.   Some people do that to save a couple thousand bytes of
> space, but on a multi-gigabyte drive, who cares about a couple thousand
> bytes.
>
> > Previously I was aiming for 5 slices, each of which had a single
> partition
> > as described below.
>
> Yup.   That won't work.
>
> > >From your explanation I take it that "slices" are what Windows refers to
> as
> > "Primary Partitions"?
> > If that's the case then I understand the behaviour I experienced.
>
> Yes.   There is that conflict of terminology.
> But, FreeBSD has called it slices from the beginning.
>
> > Is it possible to make a slice non-bootable?
>
> Yes.   Just don't put in an MBR and don't mark it bootable in
> the fdisk stage.
>
> > And would there be any benefits (less fragmentation, faster access time
> > etc.) in using slices rather than partitions to layout the harddrive or
> > should slices only be used to represent a physical harddrive?
>
> There is no advantage in making a slice non-bootable, except you might
> be able to save a few bytes of storage - storage that is not normally
> used anyway.   There is no advantage in speed or access time and
> fragmentation is only a MS worry.   It is not an issue in superior
> UNIX filesystems - at least in FreeBSD's.
>
> I don't understand the last line of that paragraph.
> Pretty much everything is virtual in disk drive addressing nowdays.
> It doesn't matter which level you refer to.
>
> The slice and its limit to 4 is a "feature" of standard BIOS basically.
> All the other things, partitions, extended partitions, etc are ways
> of getting around the limits.    The only real reason nowdays to
> have more than one slice on a drive in FreeBSD is if you want to put
> more than one bootable system on the drive.   For example, the machine
> I am typing on has MS-XP and FreeBSD, plus a Dell diagnostic slice -
> so three slices are used.   I could squish those slices down and add
> one more, say for Linux or a different version of FreeBSD if I wanted,
> but I don't.
>
> Generally, when I make a machine intended only for FreeBSD, I put all
> the disk in one bootable slice.   Then I partition that slice to
> suit me.  My pattern is usually:
>   a   /  (root)
>   b   swap         (125% of memory size)
>   c   defines the slice - not a real partition
>   d   /tmp         (used as scratch space by many utilities)
>   e   /usr
>   f   /var         (size depends on logging and databases which live here)
>   g   /home        (user home directories, plus I put some of the things
>                     that can grow unexpectedly such as /var/mail,
> /var/spool
>                     /usr/ports, /usr/local  here and make symlinks to them)
>
> Some people make just one big partition for root plus some for swap.
> I like the control I have over things my way a little better and I
> can get by with backing up and restoring more manageable chunks my way.
>
> If the machine is to be a "dual boot" as this one is,  I carve it up in
> to slices - one for each bootable system.    If it already has some
> MS thing loaded, I use some tool such as Gparted or Partition Magic
> to shrink the MS primary partition and create two or three or four
> of them.   Then I use fdisk to set up the FreeBSD slice to be bootable
> and bsdlabel to partition that slice.
> By the way, 'dual boot' is kind of a generic term referring to any
> number of bootable slices more than one.   So, it could refer to two,
> three or four actual bootable systems on the drive.
>
> Except for something like the "hidden" Dell diagnostic slice (HP and
> probably other vendors like to do that as well), MS must be in the first
> slice because it doesn't like to play well with other systems.   But, it
> does overlook the 'hidden' slices OK.  That 'hidden' attribute is ignored
> by FreeBSD.   But, since it doesn't care which slice it is in, that is
> no problem.
>
> When I have a second (or third, etc) disk on the machine, I generally
> do not make those disks bootable.   I make them just one plain slice
> each and generally, since they mostly get used as mass data storage,
> I create just one partition in that slice.   But, I have created
> more when it was useful.   One I am thinking about, it was useful to
> make more partitions in the second drive because I was using it to
> build a system to distribute to other machines and I could isolate
> that in one separate partition that way and use other partitionss
> for development space.
>
> If you have more than one drive and you want to put some bootable
> slices on each of them, you can do that by putting an MBR on each
> one, marking each slice you want bootable as such and putting the
> boot block and OS on that drive.
>
> It is a little a little confusing that there is a Master Boot Record
> and a boot block being named in such similar sounding ways.  They
> are each one sector long and are quite related, but are different
> and both are needed.
>
> To boot, the system turns control over to the BIOS.
> The BIOS does a bunch of stuff with the hardware and then looks
>  for an MBR in its list of boot devices (which you can normally
>  configure in BIOS control utility.  You usually have to break out
>  of the boot sequence early on to get in to BIOS)
> The BIOS loads the first MBR it finds and then transfers control to it.
> The MBR does some minor housekeeping and then looks for slices that
>  are marked bootable in its boot table (set by fdisk).  It also looks
>  to see it there is another disk down the line with its own MBR.
> The MBR makes up a little menu of slices on its own disk and the next
>  drive with an MBR, if any.
> Either you select one from the menu or let it take its default.
> Then the MBR marks that slice as the latest(current) one booted, loads
>  up the boot block and transfers control to it.
> The boot block does some housekeeping and causes the system to start.
> If you select that next MBR, it does just like the first - lists its
>  own bootable slices and a possible next MBR, then loads up what you
>  select and transfers control.  You can chain bootable disk this way.
>
> If either the disk's MBR or that slice's boot block are bad in some
> way, the boot fails.
>
> Generally, nowdays, most systems commit a whole track to the MBR
> and the boot block rather than just the single sector that is officially
> called for.   The other sectors are just ignored/wasted.   It is
> a trivial amount to waste.   The main reason for doing so (I think) is
> it is easier to calculate the addressing on even track or cylinder
> boundaries rather than one sector off.
>
> But, because of this, there are several third party MBRs out there
> that assume that space will be available and so they use it to create
> fancier MBRs and boot blocks, with more elaborate menu and such.  That
> is nice, but in reality, they ultimately still do exactly what the
> basic MBRs and boot blocks do.    Grub is one of the most well known
> of these extended MBRs.
>
> FreeBSD has taken the attitude of being strict about the standard
> so it can work with all systems and limits itself to the one sector
> MBR and bootblocks.   I have heard some talk of making a FreeBSD
> version of extended MBRs and bootblocks, but I don't know if anyone
> is really doing it.
>
> ////jerry
>
>
> >
> > Appreciate the clarification
> >
> > Cheers
> > Jona
> >
> > On Fri, Nov 21, 2008 at 8:55 PM, Jerry McAllister <jerrymc at msu.edu>
> wrote:
> >
> > > On Fri, Nov 21, 2008 at 08:03:58PM +0100, Jonatan Evald Buus wrote:
> > >
> > > > Greetings,
> > > > I tried to install FreeBSD 7.0 on an old server earlier today and ran
> in
> > > to
> > > > a number of issues related to slicing and labeling the disk using
> fdisk.
> > > > The drive in the machine is a 40GB Seagate Barracude (ST34001A)
> installed
> > > as
> > > > a Secondary Master on the IDE bus using LBA.
> > > > The BIOS reports that the drive has 16 sectors pr block, but little
> else.
> > > >
> > > > When accessing fdisk during install, fdisk complains that the disk
> > > geometry
> > > > is invalid and sets it to the default geometry for 40GB:
> > > > Cylinders: 4865
> > > > Heads: 255
> > > > Sectors: 63
> > > > I've tried with the following configuration based on what was
> reported by
> > > > the BIOS:
> > > > Cylinders: 19150
> > > > Heads: 255
> > > > Sectors: 16
> > > > Looking in the manual:
> > > > http://www.seagate.com/support/disc/manuals/ata/cuda7200pm.pdf,
> Seagate
> > > is
> > > > specifying the following logical characteristic:
> > > > Cylinders: 16383
> > > > Read / Write heads: 16
> > > > Sectors pr track: 63
> > > > Which of these settings should be the correct one for the fdisk
> geometry?
> > >
> > > Let the system set it and just go with what it does.
> > > Geometry is virtual nowdays.   Except in some unusual situations
> > > (on IDE) Cylinders, heads and sectors most often do not mean what
> > > they used to.   The system drivers have it all figured out.  The
> > > important thing for you is the total number of blocks/sectors.
> > >
> > > If that doesn't work, you will have to do some diagnosis, but in
> > > about 10 out of 9 times, accepting how FreeBSD sets it is correct
> > > and works.
> > >
> > >
> > > > Additionally I encountered problems during installation if splitting
> the
> > > > disk into more than 4 slices. This would cause the following error to
> be
> > > > thrown during prior to the install files being copied (when
> sysinstall
> > > was
> > > > executing the newfs commands):
> > >
> > > You cannot have more than 4 slices.
> > > The system limits you to 4 slices, identified by numbers 1..4
> > >
> > > Once you divide in to slices, each can be further divided in to
> > > up to 8 partitions, although it is really 7 because partition 'c' has
> > > special meaning and is not really available to be a real partition.
> > > Partitions are identified with alpha letters a..h - with 'c' being
> > > used to identify the whole slice.
> > >
> > > You use fdisk to create the slices (and write the MBR and set
> > > the bootable flag).
> > >
> > > Then you use bsdlabel (formerly called disklabel) to create the
> > > partitions within a slice (plus write the slice boot block.
> > >
> > > Typically, you want to make partition 'a' be the root (/) filesystem
> > > and 'b' be swap space on a bootable system slice.   Some things assume
> > > these designations.
> > >
> > > Then you newfs partitions a, d, e, f, g, h or as many as you use.
> > > But don't touch c and don't newfs b if it is to be swap.
> > >
> > > ////jerry
> > >
> > > > "Error mounting /mnt/dev/X on /mnt/usr. No such file or directory"
> > > > Using only 4 slices seems to have solved this error, however I'd like
> the
> > > > disk layout to use 5 slices as follows:
> > > > / = 512MB
> > > > swap = 2048MB (the machine has 1024MB RAM)
> > > > /tmp = 512MB
> > > > /var = 2048MB
> > > > /usr = whatever remains
> > > > I noticed that when having 5 slices, the last slice (/usr) would be
> named
> > > X
> > > > rather than ad2s5 as I'd expect (the drive was detected as ad2).
> > > > Is this behaviour related to the error in any way?
> > > > Also, is the above disk layout good for a server intended to run both
> a
> > > web
> > > > server (Apache) and a database server (PostGreSQL) ?
> > > >
> > > > Finally after installation (using only 4 slices) the system will only
> > > boot
> > > > if the FreeBSD boot manager is used.
> > >
> > > That is probably because you have created what is referred to in the
> > > documentation as a "dangerously dedicated" disk.   You can make it
> > > work that way.  FreeBSD can handle it.   But other systems will not
> > > play nicely with it.
> > >
> > > > This in turn causes a 4 menu options, all of them named "FreeBSD" to
> > > appear
> > > > during startup despite only the / slice having been set as bootable
> in
> > > fdisk
> > > > which appears to be indicated by an "A" in the flag column.
> > >
> > > Again, because you tried to do it the wrong way.   You created 4
> FreeBSD
> > > slices, probably each with an MBR and so the BIOS and the first MBR
> think
> > > they are all bootable.
> > >
> > >
> > > > Selecting the first menu item by pressing F1 will make the system
> boot as
> > > > expected.
> > > > It seems rather silly though to use a boot manager when FreeBSD is
> the
> > > only
> > > > operating system that is installed (and ever will be installed) on
> the
> > > > machine.
> > >
> > > You can put in the other non-boot manager block during installation
> > > if you want and it will only boot FreeBSD.   But, something is needed.
> > > I forget what they call it in the sysinstall screen, but you might just
> > > as well put in the FreeBSD boot manager (MBR).
> > >
> > > > If the FreeBSD boot manager is not used however and only the MBR is
> set
> > > > during installation, the system will fail at startup with error
> "Invalid
> > > > Partition Table".
> > > > Is this because the harddrive is installed as the Secondary Master on
> the
> > > > IDE bus?
> > >
> > > No, it is because you did not create any partition table (with
> bsdlabel).
> > >
> > > ////jerry
> > >
> > > >
> > > > Appreciate any input on this
> > > >
> > > > Cheers
> > > > Jona
> > > > _______________________________________________
> > > > freebsd-questions at freebsd.org mailing list
> > > > http://lists.freebsd.org/mailman/listinfo/freebsd-questions
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> > > freebsd-questions-unsubscribe at freebsd.org"
> > >
> >
> >
> >
> > --
> > JONATAN EVALD BUUS
> >
> > Executive Vice President Open Systems and Telecommunications
> >
> > Mobile US  +1 (305) 331-5242
> > Mobile DK  +45 2888 2861
> > Telephone  +1 (305) 777-0392
> > Fax.          +1 (305) 777-0449
> > jonatan.buus at cellpointmobile.com
> > www.cellpointmobile.com
> >
> > CellPoint Mobile Inc.
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> >
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-- 
JONATAN EVALD BUUS

Executive Vice President Open Systems and Telecommunications

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Telephone  +1 (305) 777-0392
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