linux-kernel - Re: [PATCH v7 0/3] console: Add persistent scrollback buffers for all VGA consoles

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Date:   Thu, 01 Dec 2016 22:03:23 +0100
From:   Manuel Schölling <manuel.schoelling@....de>
To:     Andrey Utkin <andrey_utkin@...tmail.com>
Cc:     plagnioj@...osoft.com, tomi.valkeinen@...com, jslaby@...e.cz,
        gregkh@...uxfoundation.org, kilobyte@...band.pl,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 0/3] console: Add persistent scrollback buffers for
 all VGA consoles

Hi Andrey,

On Di, 2016-11-29 at 10:01 +0000, Andrey Utkin wrote:
> On Mon, Nov 28, 2016 at 10:28:19PM +0100, Manuel Schölling wrote:
> Regarding logout scrollback clearing not working for me. ncurses-6.0-rc1
> which I tested it with is the latest available in Gentoo portage, please
> confirm whether I need any newer version, or should I tune something
> else. I'd appreciate if you also tested your patch with gentoo setup.

I finally setup gentoo running agetty (util-linux-2.26.2) and patching
the file term-utils/agetty.c with

static void termio_clear(int fd)
{
	/*
	 * Do not write a full reset (ESC c) because this destroys
	 * the unicode mode again if the terminal was in unicode
	 * mode.  Also it clears the CONSOLE_MAGIC features which
	 * are required for some languages/console-fonts.
	 * Just put the cursor to the home position (ESC [ H),
	 * erase everything below the cursor (ESC [ J), and set the
	 * scrolling region to the full window (ESC [ r)
	 */
-	write_all(fd, "\033[r\033[H\033[J", 9);
+	write_all(fd, "\033[3J\033[r\033[H\033[J", 13);
}

solves the issue with the scrollback buffer after log out.
Let me know if you agree that this is the right way to go and I will
send a patch to the maintainer of util-linux.

Thanks again for spending all this time to test the patch!

Have a good weekend!

Manuel