[gentoo-amd64] Re: Terminal control codes

[Duncan]

"Peter Humphrey" <prh@××××××××××.uk> posted
20070102170933.15EE52B6F39@×××××××××××××××.uk, excerpted below, on  Tue,
02 Jan 2007 17:09:28 +0000:

> Somewhere in the documents I read that the size of the scrollback
> buffer can be declared in a kernel command, something like
> "fbcon=scrollback:1024k. When I do that though, the kernel boots ok but
> scrollback is disabled.

Naturally, something like fbcon would require a framebuffer console, a
kernel (pre-compile) config option.  For VGACON...

You may be looking for the video= parameters, in particular
video=scrollback.  See section 5.2 of the bootprompt HOWTO, here:
http://tldp.org/HOWTO/text/BootPrompt-HOWTO.

However, IIRC the kernel folks dramatically increased the default
recently, and with kernel 2.6.19 at least (I think it was before that but
can't remember when), I've been able to eliminate that parameter from my
grub.conf entirely, and had to go look it up.  I can now scrollback the
/entire/ boot sequence, from the login prompt, all the way back thru where
init and the Gentoo initscripts take over, back thru the many pages of
kernel init itself, and even before that, where grub prints its last
output as it loads the kernel before switching to it.  I'd never seen
those lines before, as they are normally scrolled off the top of the
screen by the first kernel messages before the monitor even resets from
the grub menu graphic mode!

There are a couple caveats, however.  First, switching between VCs loses
the scrollback context, so all you have is what's actually on the screen. 
Second and this is what was actually preventing me scrolling back further
for awhile, if you reset the console font (Gentoo's consolefont service),
it resets the scroll buffer.  Since the consolefont service starts
relatively late in the process, using it means you lose most of the
boot-time scrollback, altho you can still get most of the info from syslog
and/or dmesg -- but not that last bit of grub output! =8^(

In addition to setting vga=0x0133 for a normal 132x44 character console
(720x400 px), I /had/ been setting the consolefont to gr737c-8x6, giving me
an even higher resolution while still very readable, but I've disabled
that now, sticking with 132x44, so I can scrollback the entire boot when
necessary. 132x44 is good enough for the CLI VC.  If I need more than
that, I'll start KDE and use konsole.  There may be a way to compile that
font into the kernel and use it by default, but I'm not advanced enough to
know how to do it, so...

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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