[systemd-devel] Output boot status, etc to LCD display

Lennart Poettering lennart at poettering.net
Wed Aug 13 16:38:05 PDT 2014

On Wed, 13.08.14 21:50, John Obaterspok (john.obaterspok at gmail.com) wrote:

> 2014-08-13 21:26 GMT+02:00 Lennart Poettering <lennart at poettering.net>:
> >
> > You could probably script something using socat's "PTY"
> > transport. i.e. a script that uses socat to allocate a pty, then reads
> > strings from it, and translates this to the format you need it in...
> Wouldn't that make it pretty hard to get the first messages that are
> spit out? (from the first "Welcome to Fedora 20 (Heisenbug)!"
> message?)
> Or perhaps you ment that I could read from journal afterwards?

That message isn't logged. It's just a hearty welcome string we print to
whatever is the console. It's printed really early on, very shortly
after PID 1 was invoked. Nothing else is running at that time.

If you want to hook your stuff into that you'd need to turn your stuff
into a proper kernel TTY drivers so that you can turn the kernel's
console= to it...

> I bet, my goal was just to show the green/red messages during boot
> (stripped to 20 chars wide)
> [  OK  ] Reached target Remote File Systems.
> [  OK  ] Listening on Delayed Shutdown Socket.
> [  OK  ] Listening on /dev/initctl Compatibility Named Pipe.
> [  OK  ] Reached target Paths.
> [  OK  ] Reached target Encrypted Volumes.
> ....
> information that is printed during boot, and after boot is done I
> wanted to have current IP on row 1 and perhaps something like name of
> latest failed service on row 2.

There are messages like this written to the journal, but not the exact
messages, since they container color... 

If you are OK with that you could simply run "journalctl -f |
some-script" or so...


Lennart Poettering, Red Hat

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