using an extended partition for freebsd

[John Daniels]

Hi everyone:

I am installing 4.7-REL on a PC with one PRIMARY and one EXTENDED partition.
The PRIMARY
partition is FAT and I have W98 there. I want to use the EXTENED partition
(the WHOLE partition -
there is currently nothing there) for FreeBSD but I read that FreeBSD needs
to be installed into
a PRIMARY partition.

SYSINSTALL's FDISK program has an option ("Change Type") that lets me change
the EXTENDED
partition to FreeBSD, but I don't know if it is changing the partition to
PRIMARY or just making a
cosmetic Label change. And if it is making the change, will the BIOS
recognize it (will anything
break)

Will SYSINSTALL's FDISK program do what I need it to do? If not, what tool
can I use to change
the EXTENDED partition to a PRIMARY partition?

FYI, SYSINSTALL's FDISK screen is:

Disk Name: ad0
Disk geometry: 4865 cyls/ 255 heads / 63 sectors = 78156225 (38162MB)

Offset Size End Name PType
Desc. Subtype Flags
0 63 62 -
6 unused 0
63 12594897 12594959 ad0s1 2
fat 11
12594960 65561265 78156224 ad0s2 4
extended 15
78156225 9135 78165359 - 6
unused 0


Thanks in advance,

John


(c) Copyright 2002 John Daniels. All rights reserved.




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[Jerry McAllister]

Post by John Daniels
I am installing 4.7-REL on a PC with one PRIMARY and one EXTENDED partition.
The PRIMARY
partition is FAT and I have W98 there. I want to use the EXTENED partition
(the WHOLE partition -
there is currently nothing there) for FreeBSD but I read that FreeBSD needs
to be installed into
a PRIMARY partition.

Right. An extended partition is something MS came up with to get around
some historical narrow thinking. FreeBSD doesn't need that.
It just needs slices (which are called partitions by Microsloth).

Post by John Daniels
SYSINSTALL's FDISK program has an option ("Change Type") that lets me change
the EXTENDED
partition to FreeBSD, but I don't know if it is changing the partition to
PRIMARY or just making a
cosmetic Label change. And if it is making the change, will the BIOS
recognize it (will anything
break)

Well, it really all is just label stuff. I don't know if I would
strictly call it cosmetic.

Post by John Daniels
Will SYSINSTALL's FDISK program do what I need it to do? If not, what tool
can I use to change
the EXTENDED partition to a PRIMARY partition?

If you let fdisk turn the space in to a FreeBSD slice, then it is a slice.
If it is a slice then you can install FreeBSD on it (providing it is
big enough). You will need to let it install the boot manager to
be able to dual boot.

////jerry

Post by John Daniels
Disk Name: ad0
Disk geometry: 4865 cyls/ 255 heads / 63 sectors = 78156225 (38162MB)
Offset Size End Name PType
Desc. Subtype Flags
0 63 62 -
6 unused 0
63 12594897 12594959 ad0s1 2
fat 11
12594960 65561265 78156224 ad0s2 4
extended 15
78156225 9135 78165359 - 6
unused 0
Thanks in advance,
John
(c) Copyright 2002 John Daniels. All rights reserved.
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[Gary W. Swearingen]

Post by Jerry McAllister

Post by John Daniels
I am installing 4.7-REL on a PC with one PRIMARY and one EXTENDED partition.
The PRIMARY
partition is FAT and I have W98 there. I want to use the EXTENED partition
(the WHOLE partition -
there is currently nothing there) for FreeBSD but I read that FreeBSD needs
to be installed into
a PRIMARY partition.

Under the IBM disk-layout scheme we're still using 20 years later, you
may have up to 4 primary partitions. Most software supports having one
of them being an extended partition which contains secondary partitions.
So you have two primaries, one of them extended. (I suspect that one
could manage to use multiple extended partitions with Linux, with some
rarely-used "fdisk" features, but probably causing problems for some
software.)

Post by Jerry McAllister
Right. An extended partition is something MS came up with to get around
some historical narrow thinking. FreeBSD doesn't need that.

Be careful there. The BSD OSes essentially do the same thing, except
they allow four "extended" partitions and use different internal formats
and names:
primary partition -> slice
secondary partition -> partition

I think we should use the IBM jargon. While the slice/partition jargon
is a bit cleaner, the benefit is not worth the costs in continually
needing to explain the differences in documents and support forums,
and giving newbies another reason to return to what they know best.

Post by Jerry McAllister
It just needs slices (which are called partitions by Microsloth).

Actually, it doesn't. FreeBSD can just have what it calls "partitions",
in which case there won't be a "partition table". But "they" recommend
having one slice anyway; I guess to support software (eg, on a Linux
disk) thatexpects the more common disk layout.

Post by Jerry McAllister

Post by John Daniels
SYSINSTALL's FDISK program has an option ("Change Type") that lets me change
the EXTENDED
partition to FreeBSD, but I don't know if it is changing the partition to
PRIMARY or just making a
cosmetic Label change. And if it is making the change, will the BIOS
recognize it (will anything
break)

I've never used it but it sounds like it would work OK. The BIOS
doesn't need to recognize it, though with some boot loaders, it might
need to have the "/" secondary partition in the first 1024 cylinders for
your BIOS to grab all of the boot code.

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[Jerry McAllister]

Post by Gary W. Swearingen

Post by Jerry McAllister
Right. An extended partition is something MS came up with to get around
some historical narrow thinking. FreeBSD doesn't need that.

Be careful there. The BSD OSes essentially do the same thing, except
they allow four "extended" partitions and use different internal formats
primary partition -> slice
secondary partition -> partition

Sort of, but not quite. FreeBSD partitions divide up slices in to
nice neat separately mountable (if they are made in to file systems)
independantly addressable units.

Post by Gary W. Swearingen
I think we should use the IBM jargon. While the slice/partition jargon
is a bit cleaner, the benefit is not worth the costs in continually
needing to explain the differences in documents and support forums,
and giving newbies another reason to return to what they know best.

I don't agree there. Using slice & partition within slice is more
clear thatn partition and extended partition and may make newbees
heave a sigh of relief.

Post by Gary W. Swearingen

Post by Jerry McAllister
It just needs slices (which are called partitions by Microsloth).

Actually, it doesn't. FreeBSD can just have what it calls "partitions",
in which case there won't be a "partition table". But "they" recommend
having one slice anyway; I guess to support software (eg, on a Linux
disk) thatexpects the more common disk layout.

Yes, the socalled "dangerously dedicated" disk, sure. On today's
large disks there is little reason to do it that way.

////jerry

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[Gary W. Swearingen]

Post by Jerry McAllister

Post by Gary W. Swearingen
Be careful there. The BSD OSes essentially do the same thing, except
they allow four "extended" partitions and use different internal formats
primary partition -> slice
secondary partition -> partition

Sort of, but not quite. FreeBSD partitions divide up slices in to
nice neat separately mountable (if they are made in to file systems)
independantly addressable units.

And IBM-style secondary partitions divide up an extended primary
partition in the same way, so they can even be mounted in the Unix way
under Linux and FreeBSD. It's the same concept, though FreeBSD's
has more restrictions (at least with current software).

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[Giorgos Keramidas]

Post by Gary W. Swearingen

Post by Jerry McAllister
It just needs slices (which are called partitions by Microsloth).

Actually, it doesn't. FreeBSD can just have what it calls "partitions",
in which case there won't be a "partition table". But "they" recommend
having one slice anyway; I guess to support software (eg, on a Linux
disk) thatexpects the more common disk layout.

Some (broken in my opinion) BIOS implementations will refuse or fail
to boot from disks that do not have a "valid partition table". They
are simply broken, since it's not that hard to load the master boot
record of the first system disk in memory and run its code, but their
very existence makes disks with "valid" partition tables a necessity :-/

Giorgos.

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[Gary W. Swearingen]

Post by Giorgos Keramidas

Post by Jerry McAllister
It just needs slices (which are called partitions by Microsloth).

Some (broken in my opinion) BIOS implementations will refuse or fail
to boot from disks that do not have a "valid partition table". They
are simply broken, since it's not that hard to load the master boot
record of the first system disk in memory and run its code, but their
very existence makes disks with "valid" partition tables a necessity :-/

Are you sure? I suspect that they just need 0x55aa at the end of the
MBR. Otherwise, their definition of "valid" is probably broken too, so
that you still don't need actual slices. But you couldn't set it up
without slices using just "sysinstall" in that case, I'll have to admit.

I guess we should say that FreeBSD needs slices only when slices are
needed. Many users will not need them, especially for non-boot disks,
but their use doesn't cost much and eliminates the risk of running into
software which requires their presence.

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[Giorgos Keramidas]

Post by Gary W. Swearingen

Post by Giorgos Keramidas

Post by Jerry McAllister
It just needs slices (which are called partitions by Microsloth).

Some (broken in my opinion) BIOS implementations will refuse or fail
to boot from disks that do not have a "valid partition table". They
are simply broken, since it's not that hard to load the master boot
record of the first system disk in memory and run its code, but their
very existence makes disks with "valid" partition tables a necessity :-/

Are you sure? I suspect that they just need 0x55aa at the end of the
MBR. Otherwise, their definition of "valid" is probably broken too, so
that you still don't need actual slices.

I've installed FreeBSD 4.x a few years back on a Pentium machine with
a BIOS written by AMI that refused to boot from dangerously-dedicated
disks (without a slice table), with the evil "INSERT BOOTABLE MEDIA"
message or something similar. I didn't try to find out more about the
particular BIOS version or to check if other BIOSes had similar
problems too. Simply making one primary slice of type 165 (FreeBSD)
and partitions within the disklabel of that slice solved the booting
problems. I guess that's why it was called "dangerously" dedicated
mode in sysinstall :-)

Giorgos.

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