[systemd-devel] more verbose debug info than systemd.log_level=debug?

[Mantas Mikulėnas]

On Tue, Mar 28, 2017 at 5:01 PM, Chris Murphy <lists at colorremedies.com>
wrote:

> On Mon, Mar 27, 2017 at 1:27 PM, Mantas Mikulėnas <grawity at gmail.com>
> wrote:
> > On Mon, Mar 27, 2017 at 10:20 PM, Chris Murphy <lists at colorremedies.com>
> > wrote:
> >>
> >> Ok so the dirty file system problem always happens with all pk offline
> >> updates on Fedora using either ext4 or XFS with any layout; and it's
> >> easy to reproduce.
> >>
> >> 1. Clean install any version of Fedora, defaults.
> >> 2. Once Gnome Software gives notification of updates, Restart & Install
> >> 3. System reboots, updates are applied, system reboots again.
> >> 4. Now check the journal filtering for 'fsck' and you'll see it
> >> replayed the journals; if using XFS check the filter for "XFS" and
> >> you'll see the kernel did journal replace at mount time.
> >>
> >> Basically systemd is rebooting even though the remoun-ro fails
> >> multiple times, due to plymouth running off root fs and being exempt
> >> from being killed, and then reboots anyway, leaving the file system
> >> dirty. So it seems like a flaw to me to allow an indefinite exemption
> >> from killing a process that's holding a volume rw, preventing
> >> remount-ro before reboot.
> >>
> >> So there's a risk that in other configurations this makes either ext4
> >> and XFS systems unbootable following an offline update.
> >
> >
> > So on the one hand it's probably a Plymouth bug or misconfiguration (it
> > shouldn't mark itself exempt unless it runs off an in-memory initramfs).
>
> OK. But does it even make sense to have a process exempt from killing,
> when it's going to get killed by reboot? Seems to me once we're at
> remount-ro or umount time, nothing is exempt, they need to be forcibly
> killed, clean up the file system, and then reboot.
>

Processes are killed *before* the remount/unmount stage. The primary users
of kill-exemption would therefore be daemons which *provide* access to the
root filesystem, e.g. iscsid, rpc helper daemons, or even ntfs-3g.
(Naturally these are expected to be running from the initramfs.)

So the same applies to plymouth, IMO -- it should only mark itself exempt
if it runs from the initramfs and knows that it won't interfere.

(Unrelated, but I should also mention that systemd-shutdown has a "shutdown
initramfs" feature, where it can jump *back* to the initramfs and let its
"/shutdown" script do additional cleanup steps.)

-- 
Mantas Mikulėnas <grawity at gmail.com>
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