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Re: Fixing the missing serial console after installation issue

On 09/30/2017 07:19 PM, Frank Scheiner wrote:
> Not sure, but [1] says that it should be sufficient to add all console devices
> to the kernel command line for systemd to detect and activate them, e.g.
> `console=ttyS0,9600n8` - which includes port and configuration.

Yes, I'm aware of that and that's what people usually use to enable the serial
console post installation. However, it's most likely not what we would want to
use as adding it to the kernel command line assumes that you know what type
of bootloader is being used and you would have to add case-matching for the
various bootloader types.

Please be aware that I am not talking about just fixing the serial console issue
on SPARC machines but on all architectures supported by Debian. Hence, I want
to use a generic and robust solution, not a quick hack.

> This worked for me on non-SPARC machines (on HP C and J class machines where it
> is added by palo derived from the firmware setting, POWER5 machines via yaboot
> configuration, Alpha machines through SRM boot command, etc.) with systemd,
> but I can't remember if I explicitly configured this on the Ultra 10 or SunFire V245
> I used for testing your installer images.

Again, you would need to incorporate knowledge about the bootloader. Adding a command
line parameter to PALO is performed differently as compared to GRUB, for example.

> I think headless Sun UltraSPARC systems - and maybe others like HP Itanium systems,
> too - will activate the serial console automatically without explicit
> configuration in the kernel command line - at least for kernel messages - but
> without an explicit serial console configuration in the kernel command line,
> systemd might not get the message.

You are talking about the OpenFirmware buffer which is disabled the moment the
kernel loads the actual console driver and takes over the hardware. This behavior
is independent of systemd and systemd does not behave any different than SysVInit
or Upstart which is why the code to enable serial console for those init systems
is part of the finish-install package in the first place [1].

> As alternative, [1] also explains how to configure systemd directly via a systemd unit further below (in "Serial Terminals").

Yes, that's basically what I already mentioned in my original mail. But, as I said
before, I'm not sure how to pass any serial configuration parameters using this
method. OTOH, I'm also not sure whether setting the parameters is actually

I will figure this out tomorrow by reading the documentation or just asking
systemd upstream to which I have good connections to as I am a contributor

> Or does systemd not enable a serial console for the mentioned users despite
> using a serial console configuration in the kernel command line?

What users? As you have explained yourself, systemd recognizes the console=$dev
setting from the kernel command line and uses that to spawn a getty on this
particular console.


> [1] https://anonscm.debian.org/cgit/d-i/finish-install.git/tree/finish-install.d/90console#n79

 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

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