Date: Thu, 28 Sep 1995 03:17:20 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, nate@rocky.sri.MT.net Cc: hackers@FreeBSD.org Subject: Re: Diskslice naming convention? Message-ID: <199509271717.DAA32286@godzilla.zeta.org.au>
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>> >And the numbering scheme for the slices > 4 is determined by how they
>> >fall in the first 4 slices, correct?
>>
>> Recursively.
>How do you mean? If I have 4 slices inside of the fdisk partition 1,
>the first slice in fdisk partition 2 would be (5, 6, 7, 8 are in 1)
>slice 9. Is that what you mean by recursively?
No, I just mean that the tree of slices is walked recursively to linearize
it. It happens to be walked depth-first. This could give strange orders
such as:
1 2 3 ext
|
ext 9 10 11
|
5 ext null null
|
6 ext null null
|
7 ext null null
|
8 null null null
but most fdisks generate a degenerate nearly linear tree such as:
1 2 3 ext
|
5 ext null null
|
6 ext null null
|
7 ext null null
|
8 null null null
>> >disklabel automatically translated /dev/sd0 -> /dev/rsd0c
>>
>> Disklabel automatically translates sd0 -> /dev/rsd0c. /dev/sd0 is a
>> completely different device.
>I'm still lost. I *understand* that /dev/rsd0c and /dev/sd0 are
>different (one's a block device, the other is a character device), but
>how *are* they different in what parts of the disk they represent?
/dev/rsd0c is the character device for the c partition on the first slice
on sd0 with type 0xa5 (aka the compatibility slice). /dev/sd0 is the
block device for the whole disk.
>> ># dd if=/dev/sd0 of=/dev/null
>>
>> >But if I specifically hard-code in the device
>>
>> ># dd if=/dev/sd0c of=/dev/null
>>
>> >I should get the same results.
>>
>> No, they are completely different devices. Look at them with ls -l.
>I know, but do the above commands produce the same results (modulo the
>block and character device differences).
The areas of the disk described by the two devices can be the same in
degenerate cases.
>> >Is there anyway to determine [ A DOS slice ] outside of sysinstall?
>>
>> Many. Try
>>
>> od -c /rsd0sY | head -1 | cut -c 24-44
>> dd if=/dev/rsd0sY | file - # sort of; could be improved
>*grin*. I could do this myself, but this is not recommended for a
>newbie. Is there an 'fdisk' type of way? Would it be possible to
>modify/re-write fdisk to recognize these things? If possible, how much
>work would be required to do it?
There's the fdisk inside sysinstall and in libdisk/tst01. It recognizes
extended partitions but can't create them.
Bruce
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