[systemd-devel] How to suppress "A start job is running for offline-updates" knight-rider status output?

[Lennart Poettering]

On Mi, 27.02.19 15:56, Hans de Goede (hdegoede at redhat.com) wrote:

> Hi,
>
> On 27-02-19 12:50, Lennart Poettering wrote:
> > On Mi, 27.02.19 10:40, Mantas Mikulėnas (grawity at gmail.com) wrote:
> >
> > > On Tue, Feb 26, 2019 at 7:29 PM Hans de Goede <hdegoede at redhat.com> wrote:
> > >
> > > > Hi All,
> > > >
> > > > As part of improving the boot experience:
> > > > https://fedoraproject.org/wiki/Changes/FlickerFreeBoot
> > > > https://hansdegoede.livejournal.com/20119.html
> > > >
> > > > I took a look at how applying offline updates looks
> > > > when pressing ESC to get the detailed view, pk-offline-update
> > > > then prints "dnf update" like output, but at the same time
> > > > systemd is printing:
> > > >
> > > > [   ***] A start job is running for offline-updates
> > > >
> > > > Messages to the console, the 2 get intermixed and this looks
> > > > quite bad and makes the status update of the actual
> > > > update process almost impossible to follow.
> > > >
> > > > Is there something which I can put in the
> > > >
> > > > /lib/systemd/system/system-update.target.wants/packagekit-offline-update.service
> > > > service file to suppress the knightrider status updates ?
> > > >
> > > >
> > > I think the official name is "cylon eye status updates".
> > >
> > > Hmm, I *thought* it was possible to disable this by something like
> > > flock()'ing the console device, and systemd-fsck was supposed to do that in
> > > order to avoid the job status from mixing with the "fsck: x% complete"
> > > output. But it looks like that functionality was lost, or never present,
> > > and indeed even systemd-fsck's output is trashed by the "job is running"
> > > messages, from what I remember.
> >
> > There was a plan to use BSD locks for that. But that was only a
> > plan. It's listed in the TODO list still though, but noone worked on
> > that yet.
> >
> > > Looking at source code (manager_get_show_status, unit_needs_console,
> > > exec_context_may_touch_console), the output should be disabled if at least
> > > one currently active unit has a tty as its stdin/stdout, and/or any of the
> > > tty_reset/tty_vhangup options enabled. So maybe StandardOutput=tty,
> > > TTYPath=/dev/console would achieve this?
> >
> > So, this should work, though is a bit ugly I'd say.
> >
> > My suggestion would be: the status msg indicates that start-up of the
> > offline-updates service takes awfully long, i.e. that it apparently
> > runs everything as Type=oneshot? I find that a curious choice: why
> > that? Why not use Type=simple or Type=notify or so? i.e. why delay the
> > boot transaction like this? If you don't then the status message
> > wouldn't be shown.
>
> Thank you both for your input.
>
> https://www.freedesktop.org/software/systemd/man/systemd.offline-updates.html
>
> Says:
>
> "The upgrade scripts should exit only after the update is finished. It is expected that the service which performs the upgrade will cause the machine to reboot after it is done. If the system-update.target is successfully reached, i.e. all update services have run, and the /system-update symlink still exists, it will be removed and the machine rebooted as a safety measure."
>
> Which AFAIK means that if we make the service consider being "started"
> sooner then the system-update.target will be considered reached and the
> "the machine <will be> rebooted as a safety measure."
>
> So maybe using StandardOutput=tty + TTYPath=/dev/console is not
> such a bad idea in this case?

Another option is to do this in your soruces btw:

```c
(void) kill(1, SIGRTMIN+21);
```

Sending SIGRTMIN+21 to PID 1 will disable the status output
explicitly. If you are sure you don't want it you can just do that, in
one line.

Plymouth also sends that signal, hence make sure you don't run into
races with that.

Lennart

--
Lennart Poettering, Red Hat