Re: Use of installer's interactive shells on tty1-tty4
On Mon 14 Sep 2020 at 19:48:37 (+1000), David wrote:
> On Mon, 14 Sep 2020 at 04:05, Felix Miata <mrmazda@earthlink.net> wrote:
> > Richard Owlett composed on 2020-09-13 05:15 (UTC-0500):
>
> > > Where can I find description of using installer's interactive shells on
> > > tty1-tty4?
>
> > 1,3,4 are not available shells.
> > IIRC:
>
> That does not match my recent experience.
Ditto.
> To explore and confirm and maybe learn something from
> smarter people, I report below some actual test results:
>
> I begin by booting the buster installer on real hardware,
> and it stops at "Debian installer main menu".
>
> Pressing alt-F2 or alt-F3 produces a prompt
> "Please press Enter to activate this console."
> and pressing Enter starts BusyBox.
> Pressing alt-F4 displays logs.
> Pressing alt-F5 or any higher F-key does nothing.
You can also confirm this by pressing Alt-→ and Alt-← to rotate
through the four VCs.
> Pressing alt-F1 returns to the installer.
>
> BusyBox 'tty' command confirms /dev/tty2 and /dev/tty3.
>
> 'echo foo >/dev/tty4' confirms that the log display is
> /dev/tty4 when the string 'foo' appears there.
>
> I was unable to find any evidence for the use of /dev/tty1,
> apart from pressing alt-F1 working as expected.
>
> But I was just poking around cluelessly for curiosity, someone
> else might know a way to do that. BusyBox 'ps' appears to not
> provide tty information.
>
> In BusyBox, 'ls -R' appears unsupported, so I ran:
> find /proc -type d -exec ls -l '{}' \; 2>/dev/null | grep tty1
> it gave no output.
>
> I looked at the other active processes using the same methods
> without discovering anything else about /dev/tty1.
>
> The installer PID was 257.
> ls -l /proc/257/fd/
> shows
> 2 -> /dev/tty0
>
> BusyBox 'echo' to /dev/tty0 did not affect the installer screen.
>
> However, I saw that process '/usr/bin/main-menu' used /dev/pts/0
> and 'echo' to that device did write text into the installer screen.
>
> At the "Debian installer main menu" I activated the
> "Execute a shell" menu entry. In this shell
> $ tty
> /dev/pts/0
>
> It appears that /dev/pts/0 performs the role of /dev/tty1.
You found it. That's the shell I said I've never used, available
on VC1 for those unlucky enough to find no means of leaving VC1
(eg Alt/Windows/etc keys not functioning correctly):
> I'm not very knowledgeable about all this tty stuff so I will leave
> it at that.
Same here. An interesting search.
Cheers,
David.
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