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List:       dragonfly-bugs
Subject:    Re: HAMMER: you can mount_hammer a UFS that was a hammer fs before
From:       Bill Hacker <wbh () conducive ! org>
Date:       2009-10-27 3:45:07
Message-ID: 4ae66cd5$0$882$415eb37d () crater_reader ! dragonflybsd ! org
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Matthew Dillon wrote:
>    Well, this is basically simply due to the fact that the volume headers
>    are in different places and HAMMER and UFS's initial data layout winds
>    up being non-conflicting.  But clearly it isn't going to stay that way
>    for long.

:-)

.. perusing with the hex editor IS a mite tedious, if highly educational..

> 
>    It's a fun exercise and we should probably adjust newfs for UFS and HAMMER
>    to clean out a few extra megabytes at the beginning of the partition to
>    ensure that any prior volume header is overwritten, but it isn't really
>    a bug per-say.  The filesystem type in the partition editor is the more
>    definitive information source.
> 
> 					-Matt
> 					Matthew Dillon 
> 					<dillon@backplane.com>

Reality is that with the commonality of movable media, it has become more 
obvious that every OS on the planet makes 'complacent'  - hence potentially 
dangerous - assumptions based on partial look at labels and such - legacy MBR + 
and newer GPT included. Sometimes on the basis of less than a full Byte.

DFLY cannot boil THAT ocean. Not on its own, anyway.

Also clearly impractical as well as vanishingly irrelevant to worry about what
OS/2 //eCS, MorphOS, ForthOS, BeOS/Haiku, HelenOS, Minix, Plan9, VisopSys, 
TuDOS, AoS Bluebottle, Syllable, Menuet, QNX - just to name those on media 
within arm's length of my *own* keyboard -  might see or do.

Folk who trifle with those *expect* to be odd-man out.

But DFLY could at least provide clues that reduce the risk of the most commonly 
attached hosts assuming the 'wrong thing', to wit:

- Win / DOS

- Linux

- The *BSD's (Mac especially - as it is near-as-dammit blind by choice..)

And perhaps even:

- Solaris, AIX, HP-UX

None of these have to be made to ID hammer fs, let alone mount it.

Just be 'tricked' into leaving it the f*** alone. E.G. - look like 'unavailable' 
or 'weird' - not 'empty space'.

See:

http://www.win.tue.nl/%7Eaeb/partitions/partition_types-1.html

.. but one of many often conflicting resources. And that is another problem. 
Dearth of true 'standards'.

If the carefully-crafted longevity-focused hammer fs is really to someday be 
trusted with the 'crown jewels', it may help to reduce its exposure to being 
totally trashed by the wrong bit of cable accidentally plugged in.....

'BT,DT,GTTS - WBH'

Bill
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