[systemd-devel] vt220 default for serial console still relevant?

[Barry]

> On 11 Jul 2020, at 20:31, Daan De Meyer <daan.j.demeyer at gmail.com> wrote:
> 
> 
> > TERM=linux means Linux console, but that's just too much, as it not
> > only implies a multitude of ESC sequences specific to the Linux
> > console, but also indicates that certain ioctls might work. In our own
> > code we also bind certain behaviour to TERM=linux, as indicator if we
> > are on the Linux console.
> >
> > I am not aware of any widely-supported TERM value that would be a
> > reasonable subset of all currently used terminals and does color.
> 
> I did some more research and it turns out VT220 does support colors. My terminal emulator (Konsole) just doesn't seem to support it. I installed xterm (which explicitly advertises support for VT220 escape codes) and got colored output as expected.  I guess this means it's up to Konsole to support more of VT220 if I want this to work seamlessly (or I switch terminals to xterm).
> 

No vt220 does not support colour. I used to work on one and it is monochrome hardware.
Xterm and konsole support extensions beyond vt220 that add in the colour support.

Barry

> Thanks for the extra info and context.
> 
> Daan
> 
>> On Sat, 11 Jul 2020 at 20:04, Lennart Poettering <lennart at poettering.net> wrote:
>> On Sa, 11.07.20 17:51, Daan De Meyer (daan.j.demeyer at gmail.com) wrote:
>> 
>> > Hi,
>> >
>> > I was playing around with mkosi's qemu support, more specifically adding
>> > the -nographic option to have the virtual machine output in my terminal
>> > instead of a separate window. After figuring out that I had to add
>> > console=ttyS0 to mkosi's kernel command line, I got the output from the vm
>> > in my terminal as expected. However, because systemd defaults to TERM=vt220
>> > for serial consoles, the output is not colorized. I searched around a bit
>> > and found that this is done for compatibility reasons. Will there ever be a
>> > point where we can switch the default to something that supports colors
>> > (like TERM=linux)?
>> 
>> TERM=linux means Linux console, but that's just too much, as it not
>> only implies a multitude of ESC sequences specific to the Linux
>> console, but also indicates that certain ioctls might work. In our own
>> code we also bind certain behaviour to TERM=linux, as indicator if we
>> are on the Linux console.
>> 
>> I am not aware of any widely-supported TERM value that would be a
>> reasonable subset of all currently used terminals and does color.
>> 
>> > I managed to get around the problem by overriding serial-getty at ttyS0 and
>> > setting Environment=TERM=linux explicitly but it's a bit of a pain and has
>> > to be added to every rootfs that wants to support colored output on its
>> > serial console.
>> 
>> Unfortunately we can't guess the right terminal, we cannot propagate
>> TERM=xterm or TERM=linux depending if you invoke qemu on an xterm or
>> from a Linux console, hence the best thing we can do is stick to a
>> reasonably powerful subset that is likely going to exist everywhere,
>> and that's vt220 right now, as noone had a better suggestion so far...
>> 
>> Lennart
>> 
>> --
>> Lennart Poettering, Berlin
> _______________________________________________
> systemd-devel mailing list
> systemd-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/systemd-devel
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/systemd-devel/attachments/20200713/f107e5f4/attachment.htm>