[TUHS] Determining what was on a tape back in the day

Dave Horsfall dave at horsfall.org
Tue Nov 21 09:22:28 AEST 2017


On Mon, 20 Nov 2017, Random832 wrote:

> For whatever it's worth, the tm(4) and ht(4) manpages from V5 onward say 
> "seeks have their usual meaning", and both drivers provide a 'non-raw' 
> device which is a block device and (according to the manual) only 
> supports tapes consisting of 512-byte records - the BUGS section 
> mentions that the raw device, conversely, does *not* support seeking.

Thank you; I dimly recall that seeks were implemented by the driver 
keeping track of whichever block was under the head, and skipping forwards 
or backwards accordingly, with simple arithmetic. I no longer have access 
to those sources, but we at UNSW certainly modified Unix rather heavily, 
so if that capability is not in the distributed version then it means that 
we modified it; this was over 30 years ago...

It bloody well worked as a read-only file system; I take great umbrage 
at the implication that I am a liar, and I'm the sort of obstreperous 
bastard who neither forgives not forgets...

-- 
Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will suffer."


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