[lubuntu-devel] "TTY" goes to black screen, then doesn't come out of it?

[Fritz Hudnut]

Walter:

Thanks for the data . . . seems like in the case of Lu on my computer it is
F1 that returns the GUI . . . hilarious.

F

On Sat, Jan 25, 2020 at 11:36 PM Walter Lapchynski <wxl at ubuntu.com> wrote:

> On Sat, Jan 25, 2020 at 03:06:28PM -0800, Fritz Hudnut wrote:
> > I was going to boot Lu 20.04…but for some reason the
> > computer booted U-MATE 20.04
>
> Oh, these computers and their capricious ways… 😉
>
> > I guess the only one I didn't try was F1???
>
> "You never know until you find out"
>     ­ [Ned's Atomic Dustbin][1]
>
> Incidentially, I have seen cases where the key to return to the GUI was
> F7 and cases where it was F1, across different Ubuntu flavors.
>
> It's always true that the number of active ttys is six, as you
> can see with `grep tty /etc/default/console-setup`. You can also see
> this in `systemd` with `grep NAutoVTs /etc/systemd/logind.conf`. An
> interesting thing about at least current systemd is that ttys are
> created on-demand thus the reason for "Auto" in that key.
>
> The kernel gives a lot more (`ls -h /dev/tty[1-9]* | wc -l` says 63) but
> only the ttys that have getty running on them are accessible as
> virtual terminals. X runs on a tty that doesn't have getty running.
> You can see what's going on with something like
>
>     for t in {1..7}; do ps --no-headers --tty /dev/tty$t; done
>
> That said, all twelve function keys are defined with control and alt to
> switch between the different ttys (aka consoles, virtual terminals),
> which you can see with the likes of
>
>     dumpkeys | grep \
>     "^[[:space:]]*control[[:space:]]*alt[[:space:]]*keycode.*Console_"
>
> Actually, if you just do `dumpkeys | grep Console` you'll find there are
> a whole plethora of shortcuts for switching between the terminals.
>
> The only question remaining is why does X end up on tty7 sometimes and
> other times not? Actually, I think this is circumstantial. Lubuntu
> 18.04 and previous, like Ubuntu MATE and Ubuntu proper and every other
> flavor of Ubuntu except for Kubuntu, all used lightdm for their display
> manager. Kubuntu has long used sddm, and so has Lubuntu since after
> 18.04. Incidentially, the two display managers have different feelings
> about what tty to use.
>
> In lightdm's case, [they've had it set to 7 for 9 years][2], ever since
> they first added support for users to define the specific tty you want
> to use. This is changed to use 1 simply by editing
> /etc/lightdm/lightdm.conf (you will likely have to create it) as such
> and then restarting the display manager
>
>     [LightDM]
>     minimum-vt=1
>
> In regards to sddm, [when they added support for a specific tty][3],
> they set the default as 7. However, when systemd came around, they
> [conditionally set it to 1 or 7][4] with the former being preferred in
> the case of systemd. Why that is, I don't know, but it's easily changed
> as above, except in this case, with /etc/sddm.conf, to 7 with
>
>     [X11]
>     MinimumVT=7
>
> So, ok, maybe some things are a bit different. But not really.
>
> [1]: https://www.youtube.com/watch?v=LlMB9svNRzo
> [2]:
>
> https://github.com/canonical/lightdm/commit/5372aa1c34db925fabae586e6003d58908e9e307
> [3]:
>
> https://github.com/sddm/sddm/commit/af8d253d119104ec37059f8920aceae6b204b307
> [4]:
>
> https://github.com/sddm/sddm/commit/3f9c18b5129a7110c5974036feb8b210f46ffc4a
>
> --
>        @wxl | polka.bike
> C563 CAC5 8BE1 2F22 A49D
> 68F6 8B57 A48B C4F2 051A
>
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