"The AppStream system cache was updated, but some components were ignored. Refer to the verbose log for more information."

Status changed to 'Confirmed' because the bug affects multiple users.

This error message is shown not to alert users, but rather make users report these issues to the distributor, as this particular issue means the distributor has a mistake in their metadata somewhere.
In this case it's not Ubuntu's fault directly, but rather GNOME Software injecting invalid metadata.
This is fixed upstream with commit https://gitlab.gnome.org/GNOME/gnome-software/commit/7c1620990b6361fac370b76c9828f8f77ff77a72 which should land in the next Ubuntu release naturally (but may be cherry-picked to make this issue go away even sooner).

I believe this error message needs rework, people have no idea what AppStream is or where they can find the verbose log or why they even see that.

Agreed, if the intent is for people to file bugs then it should be clearer.

(Alternatively, might there be a better way for us to report this on Ubuntu as a "crash", if users truly can't do anything about it?)

Technically, PPAs with AppStream data or other repositories with broken data can trigger this as well.
AppStream could make a guess who is to blame for the breakage and give a more specific error, but that will require some more extensive code changes.

This bug is still present because the change that Matthias did was unintentionally undone the following week. So it was not shipped as it should have been, as part of gnome-software 3.35.91, which is the current version in Ubuntu. I have signaled this issue upstream.

Is there a fix yet, I too have this error.

The fix was made upstream on Mar 24 [1], released as part of gnome-software 3.36 on Apr 3 [2], which was packaged for Ubuntu today Apr 6 [3]. I'd say it's just a matter of hours before it's available in the repository :)

[1] https://gitlab.gnome.org/GNOME/gnome-software/-/commit/bb7f58f5f88381857cd9b5dbe608e75d459873f1
[2] https://gitlab.gnome.org/GNOME/gnome-software/-/commits/gnome-3-36
[3] https://launchpadlibrarian.net/473131226/gnome-software_3.36.0-0ubuntu1_source.changes

Please disregard my previous comment. Looking at the code, I realize that the maintainer packaged the upstream gnome-software "3.36.0" tag, not the "gnome-3-36" branch, which makes a lot more sense indeed.

So even though the fix is made upstream, it is NOT YET released, and therefore not packaged for Ubuntu. I think this bug is stuck until upstream releases 3.36.1.

With the replacement of gnome-software by snap-store in 20.04, this bug is no longer apparent. Only users who manually (re-)install gnome-software will see it.

>With the replacement of gnome-software by snap-store in 20.04, this bug is no longer apparent. Only users who manually (re-)install gnome-software will see it.

I am not sure what you mean. There is no "snap-store" deb on my 20.04 system, nor does "apt search snap-store" yield any results.

Furthermore, this bug was initially reported about the output of apticron showing up in cron job emails; as far as I know, apticron is independent of gnome-software.

Please clarify your meaning.

On Tue, Apr 14, 2020 at 11:19:53AM -0000, Naël wrote:
> With the replacement of gnome-software by snap-store in 20.04, this bug
> is no longer apparent. Only users who manually (re-)install gnome-
> software will see it.

I have an up-to-date focal system and I am still seeing this.

Hi Jonathan and Dan:

> I am not sure what you mean. There is no "snap-store" deb on my
> 20.04 system, nor does "apt search snap-store" yield any results.

It's a snap application, which you'll see in the output of the "snap list" command if it is installed. It provides the Ubuntu Software application on 20.04 and replaces the "gnome-software" deb, cf https://discourse.ubuntu.com/t/is-ubuntu-software-going-to-be-remove-for-snap-snap-store/14542 and bug 1868409.

If I understand correctly, at this point in time, your system shouldn't have the "gnome-software" deb any longer unless you've manually installed it yourself, and it should have the "snap-store" snap instead.

> Furthermore, this bug was initially reported about the output of
> apticron showing up in cron job emails; as far as I know, apticron
> is independent of gnome-software.

This is unclear to me too, but Matthias Klumpp identified the cause of this error as lying with gnome-software metadata, and he fixed it upstream in gnome-software, cf comment 3 on this bug. Perhaps apticron runs apt-get update?

> I have an up-to-date focal system and I am still seeing this.

I don't see it any more. The plot thickens. You may still have the "gnome-software" deb? If yes, and you don't mind migrating to the "snap-store" snap for you Ubuntu Software application, then you could run the update-manager (the graphical application), it will take care of the transition, see bug 1868409 for details.

I think Naël is correct that this problem goes away when gnome-software is replaced by snap-store. Or, at least, it appears to have gone away for me when I did that.

I'm a bit concerned about that, though, because the reason why I didn't get that update is because I pretty much exclusively use apt to do my updates, and apparently that's no longer sufficient to get all the updates needed on an Ubuntu system. I don't want to have to run the graphical update-manager to do updates. I know this is mostly off-topic here, but I don't suppose anyone knows whether there is a way to do the equivalent of what update-manager does, but from the command line?

On Wed, Apr 22, 2020 at 10:24:41AM -0000, Jonathan Kamens wrote:
> I'm a bit concerned about that, though, because the reason why I didn't
> get that update is because I pretty much exclusively use apt to do my
> updates, and apparently that's no longer sufficient to get all the
> updates needed on an Ubuntu system. I don't want to have to run the
> graphical update-manager to do updates. I know this is mostly off-topic
> here, but I don't suppose anyone knows whether there is a way to do the
> equivalent of what update-manager does, but from the command line?

Snaps are updated ("refreshed" in snap terms) automatically by snapd,
independent of the other update mechanisms for the system. If you run
`snap changes` after a system (with snaps installed, of course) has been
up for a few hours, you should see entries like:

ID Status Spawn Ready Summary
263 Done yesterday at 17:53 EDT yesterday at 17:53 EDT Auto-refresh snap "gtk-common-themes"
264 Done today at 03:03 EDT today at 03:04 EDT Auto-refresh snap "lxd"

I understand that, but in this particular case we're talking about a transition from a deb to a snap, not a snap update. Apparently there's special logic in update-manager to handle this, and perhaps in do-release-upgrade as well, but I don't think either apt nor snap auto-updates will handle this.

On Wed, Apr 22, 2020 at 02:53:48PM -0000, Jonathan Kamens wrote:
> I understand that, but in this particular case we're talking about a
> transition from a deb to a snap, not a snap update.

Aha, apologies, I misread your previous comment.

> Apparently there's special logic in update-manager to handle this, and
> perhaps in do- release-upgrade as well, but I don't think either apt
> nor snap auto- updates will handle this.

There has been special logic in update-manager for other cases before,
but this is not my area of expertise so I'll leave others to comment
further. :)

Hi Jonathan and Dan:

> I don't think either apt nor snap auto-updates will handle this.

I don't think so either, and nor will manual snap updates ("snap refresh" command).

My assumption is that deb-to-snap and snap-to-deb transitions are limited to development releases. It would be very surprising to have such transitions happen once a release is out, wouldn't it? But then again I don't know.

Canonical's Marcus Tomlinson, who implemented the special deb-to-snap/snap-to-deb logic in update-manager to fix bug 1868409 and bug 1872958, could tell us more, and let us know if we now need to do more than run apt to keep our systems up-to-date. But I'm not sure how to contact him or his team. This bug, or Launchpad in general, don't seem like the right place, as it's not a bug. Perhaps a mailing list (which one?), the Freenode IRC network (which channel?), Ubuntu Discourse or Ask Ubuntu are better places for this question.

Jonathan:

Actually that sounds like a question for the update-manager developers, so I've asked it there and subscribed you to it: https://answers.launchpad.net/ubuntu/+source/update-manager/+question/690201

Matthias:

Thanks for the downstream patch! It's awesome to see this fixed without having to wait for a new upstream version.