about freebsd partition problem

Ian Smith smithi at nimnet.asn.au
Mon Jun 19 09:42:53 UTC 2006

On Mon, 12 Jun 2006 freebsd-questions Digest, Vol 138, Issue 5 wrote:

 > To: standardhk at gmail.com (t s)

 > > my harddisk(40G FAT32) :
 > > c:\ (primary 10G windows XP root)

That's one slice (DOS: partition)

 > > d:\ (logical 5G with data)
 > > e:\ (logical 5G with data)
 > > f:\ (logical 10G with data)
 > > g:\ (logical 10G empty)

And all of those DOS logical drives are probably within slice (ad0s2)
Unless things have changed with XP, s/probably/certainly/

 > > so i want to release 500MB from "d:\" for the second primary partition
 > > and then put the freebsd "/" on it, the other put to "g:\" just like the
 > > belows:
 > > 
 > > windows xp mode
 > > c:\ (primary 10G windows XP root)

That much is fine, best (probably still essential) to have your DOS on
the first slice (DOS: partition) ad0s1.  Preferably FAT32 if you need to
read/write it from FreeBSD, but read-only NTFS is said to work.

 > > d:\ (logical 4.5G with data) ====> 500MB for freebsd "/" (second primary
 > > "ad0s2")

ad0s2 is the whole slice (DOS: primary partition) from which DOS logical
drives are allocated.  Here 'drive d:' might be mount_msdos'd as ad0s5,
e: as ad0s6 and f: as ad0s7 etc.  Weird but it works; this was how I got
to recover (ro was all I dared) previous OS/2 HPFS partitions years ago.

 > > e:\ (logical 5G with data)
 > > f:\ (logical 10G with data)
 > > cannot see the g:\ ==========> used by /var /usr /swap

Do you (Steve) have a third slice ad0s3 allocated for /var /usr & swap? 

 > > is it ok??? but i don't know how to create the "ad0s2"??? and edit the g:\
 > > for /var, /usr, /swap???
 > Well, sort of OK.   I would not be inclined to put a FreeBSD slice
 > right in the middle of your MS logical drives.   But, I think you
 > could do it.   

I don't believe so, Jerry.  Unlike Linux, you can't install FreeBSD on
other than what BIOS/DOS calls a primary (MBR) partition, and we call a
slice (to save a message, I appreciated your upcoming FAQ about that!)

 > Secondly, I don't know what just having 500 MB for a FreeBSD '/' would
 > get you.   It would not be enough to run FreeBSD.   But, probably you
 > haven't told the whole story.   Something else must be there.  Anyway,
 > I would be inclined to take the FreeBSD slice out of that empty GB
 > space that currently shows up as g: on you Microsloth system.

Not unless it's another primary MBR / fdisk partition, but yes it's not
clear.  I'm not sure of the wisdom of only having / in one slice, and
/usr, /var (and swap) on another, though you can.  I'd use DOS fdisk to
remove one or more of those 'logical drives' then PM or something to
consolidate free space, and put FreeBSD on ad0s3, 10G at least :) 

 > > any disk edit tool can do it???
 > I have successfully used Partition Magic for this sort of thing.  
 > It is available at not too high a price from most places that
 > sell software.    As long as all the MS stuff is FAT, I think
 > there are some free tools that will work too, but I haven't used
 > them so can not attest to their effectiveness or reliability.
 > A couple come with the FreeBSD distribution.   But, the free tools
 > do not handle NTFS which is why I haven't used them.

If Steve places much value on the data on other than his c: (ad0s1) then
investing in Partition Magic might be wise.  I've used presizer in
fingers-crossed mode to shrink whole-disk-as-C: setups, and it worked,
but there was nothing precious there.

 > You will first need to use the disk tool such as Partition Magic
 > to shrink the existing structures and put a new primary slice in
 > the space.   


 > Then, when you run the FreeBSD install, you have it mark the slice as 
 > a FreeBSD slice.  Up until that point, it is not really a FreeBSD ad0s2,
 > just some generic space.    Partition Magic does not know how to mark
 > the slice (which it calls a primary partition, using MS terminology)
 > as a FreeBSD slice.    So FreeBSD's fdisk does it.   (Even if you
 > use sysinstall to write the slice, it really just calls fdisk)

Yes, but if he wants to keep some of his 'logical drives' they'll stay
in ad0s2 (accessed as above as ad0s[567]) and ad0s3 will be FreeBSD, no?

Cheers, Ian

 > Good luck,
 > ////jerry 
 > > 
 > > thank you very much
 > > 
 > > steve (come from hong kong)

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