Sharpe, Sam J wrote:
I have to say that I haven't had a lot of experience with s390 or
"unusual architectures" but all of the "Enterprise" kit *we* buy has
methods to at least get a text, if not graphical console on a machine
without SSH to the main interface - but Greg is right, it's the WTF in
the Manual that they need to address then (and what the heck is the
point of a --ssh flag if it's not optional?).
S/390 - zSeries - doesn't do graphics. If you want graphics, you do in
in a peripheral.
Generally speaking, it doesn't do async (character-by-character) I/O
either. Terminals send all the data when you press <enter> (or some
other select keys). Line printers take (if they still exist!) a line at
a time, maybe several depending on the programming. All I/O is done by
peripheral computers.
The block mode of I/O doesn't fit well with the historic Unix model of
character-by-character.
A channel program from the S/360 era to read data from disk might go:
07 ..... seek Position to cylinder/track
31 .... read key to next block, compare with storage
08 .... (generally) jump back to previous instruction, only if -ne-
02 .... Some kind of read, likely some other read op-code.
Generally, the OS would add commands to preposition the heads (the seek
above) and to prevent reading past track/cylinder boundaries (there are
multitrack reads).
Ordinarily, the host CPU program prepares the channel program than
passes it over to the channel for processing. The channel interrupts
when the program's completed. In the case of remote terminals, that
could be hours later.
Having the ssh port open is good, when the initial install uses ssh and
(maybe) if it uses vnc. That should be enough to address Chris Lumens'
concern. I can understand reluctance to make the install more
hardware-dependant than necessary, but _this_ infers an outcome
compatible with the users' installation choice.
--
Cheers
John
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