Re: Serial console

[Yoshinori K. Okuji]

At Thu, 11 Apr 2002 23:53:08 +0200,
Christoph Plattner wrote:
> Let's try with the new status of knowledge:
> 
> * GRUB only support 2 kinds of console: one is serial, the other is 
>   VGA/KBD.

That's not correct. Hercules is also supported. I think a kind of
"network console" will be added, but this is just a plan which may or
may not realize.

> * While the timeout is running, all (= 2) consoles are "polled" if
>   a user reaction is detected, if one is detected, then this device
>   is select as console device. Correct ?
> * If the timeout runs out, then the console type is used, which is given
>   as parameter in the `terminal' call.

A bit different. GRUB polls only terminals specified to "terminal" by
the user. For example, if you enter "terminal serial", console is not
polled. With "terminal hercules console", GRUB polls hercules and
console but not serial.

When the timeout expires, GRUB selects the first argument to
"terminal" as the default terminal. For example, if you specify
"terminal --timeout=10 console serial", console will be selected,
unless you input anything. Likewise, if you specify "terminal
--timeout=10 serial console", serial will be selected.

> A system canbe configured to a "serial console" or to a "...." (and this
> is the difficult part !), for example "screen/keyboard" is often used
> on UNIX machines, "VGA/keyboard" is also suitable for PC architecture.

I agree that the terminology is not very good, and it is really
difficult to choose a good wording.

But I think the current one is not so bad. To quote from The Jargon
File:
> console
> n.
> 1. The operator's station of a {mainframe(->link)}. In times past, this
> was a privileged location that conveyed godlike powers to anyone with
> fingers on its keys. Under Unix and other modern timesharing OSes, such
> privileges are guarded by passwords instead, and the console is just the
> {tty(->link)} the system was booted from. Some of the mystique remains,
> however, and it is traditional for sysadmins to post urgent messages to
> all users from the console (on Unix, /dev/console).
> 2. On microcomputer Unix boxes, the main screen and keyboard (as opposed
> to character-only terminals talking to a serial port). Typically only
> the console can do real graphics or run {X(->link)}.

The second description matches my use of the word "console".

Perhaps the bad thing is just that the manual doesn't explain how the
terms will be used before they are really used.

Okuji