Dangerous file system / disk problem

Ben Paley ben at spooty.net
Sun Jun 6 11:34:40 PDT 2004

On Sunday 06 June 2004 13:04, Dan Strick wrote:

> Perhaps something changed the partition type code in the MBR partition
> table on your FreeBSD disk.  Do "fdisk ad1" to display the MBR partition
> table.  The FreeBSD slice should say:
> 	sysid 165,(FreeBSD/NetBSD/386BSD)
> If it says anything else, you can use the command "fdisk -u ad1" to
> change the MBR partition type code back to 165 (decimal).

su-2.05b# fdisk ad1
******* Working on device /dev/ad1 *******
parameters extracted from in-core disklabel are:
cylinders=155061 heads=16 sectors/track=63 (1008 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=155061 heads=16 sectors/track=63 (1008 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
    start 63, size 156296322 (76316 Meg), flag 80 (active)
        beg: cyl 0/ head 1/ sector 1;
        end: cyl 1023/ head 254/ sector 63
The data for partition 2 is:
sysid 14 (0x0e),(Primary 'big' DOS (>= 32MB, LBA))
    start 156296385, size 0 (0 Meg), flag 0
        beg: cyl 1022/ head 0/ sector 1;
        end: cyl 1022/ head 254/ sector 63
The data for partition 3 is:
The data for partition 4 is:

I don't really understand this, frankly: it certainly gives the right 
partition type code for the main partition, but I'm not sure of the relevance 
of the other stuff... does it look ok to you? Or is this "partition 2" where 
the problem is? Partition Magic in Windows sees only one partition on that 
disk. The slice editor in sysinstall shows this for ad1:

Offset		Size(ST)		End			Name	PType	Desc		Subtype    Flags

0			63			62			-		12		unused	0
63			156296322		156296384 	ad1s1	8		freebsd	165
156296385		5103			156301487		-		12		unused	0

> (Which release of FreeBSD do you run?  You used the "bsdlabel" command
> to display the FreeBSD disk label on /dev/ad1s1.  That suggests you
> are running FreeBSD 5.x.  In my experience, release 5.x won't recognize
> FreeBSD disk labels in non FreeBSD slices and won't create special
> files for the partitions in /dev.  This suggests that your MBR partition
> type code is actually correct.  I dunno ... but it should be worth
> checking anyway.)

5.2-CURRENT. But BSD sees everything ok, it's Windows that's having a problem. 
I don't feel confident making any changes in Windows, however, because it 
seems as though my only option there would be to format the partition! Which, 
from a Windows point of view, would certainly be a solution of sorts...

Thanks for your help,

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