[systemd-devel] How to get systemd boot messages on serial console and screen?

[Lennart Poettering]

On Tue, 14.04.15 13:36, Frank Steiner (fsteiner-mail1 at bio.ifi.lmu.de) wrote:

> Hi,
> 
> when adding "console=tty0 console=ttyS4,115200" as kernel parameter
> on my SLES 12 systems I get all kernel messages both on the physical
> screen and over the serial console.
> But the systemd messages about the services started appear only on
> ttyS4.
> 
> When I switch the order, i.e. tty0 after ttyS4, I still get kernel
> messages on both, but the systemd messages only show up on the screen.
> Gettys are always started on both consoles.
> 
> The SuSE support told me I must have plymouth installed and indeed,
> when doing so, the systemd messages are printed on ttyS4 and the screen.
> But plymouth causes others problems on my systems so I would like
> to avoid it.
> 
> Is there a way (without plymouth) to make systemd print its boot messages
> on all consoles specified in the kernel parameters? From the man pages
> and googling around I'm not sure if systemd should be doing this by
> default or not.

We write the status output to /dev/console, see status_vprintf():

http://cgit.freedesktop.org/systemd/systemd/tree/src/shared/terminal-util.c#n643

Usually the kernel will forward what is written to /dev/console to all
console= terminals listed on the kernel cmdline.

Check the contents of /sys/class/tty/console/active to see which
ttys those currently are.

I know the the suse folks patched around in this area of systemd,
please consider asking them for details in this areas!

Lennart

-- 
Lennart Poettering, Red Hat