21 Nov
2017
21 Nov
'17
12:35 a.m.
Dave Horsfall wrote:
On Mon, 20 Nov 2017, Random832 wrote:
I know that a read-only filesystem for installs is possible. Pyramid
Technologies used a tape install filesystem called ROFS...guess what
that stands for...
We used it on both cartridge (QIC-150 iirc) and 9 track magtapes... So
there's no special type of drive needed.
It was created by dd-ing a chrooted specially constructed file tree
(IIRC). I constructed special ones at my
site with all the site specific info (passwords, groups, etc) on it for
emergency recovery.
It was used for their OS/x (BSD-SysV dual universe for their Risc CPU)
and DCOSx (SVR4 port to Mips R3000).
Bill
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...