[Bug 1969162] Re: bad interaction between snapd and update-notifier when snapd package is being upgraded

[Alberto Mardegan]

Hi Steve, thanks for reporting this, and for the hint on how to fix it.
We currently have a shell script in our prerm script, which manually
stops all our systemd units:

https://github.com/snapcore/snapd/blob/master/packaging/ubuntu-16.04/snapd.prerm

Do I correctly understand that your suggestion is not to do that?

I'm actually a bit confused (though this is probably a question for my
own team) why we have that prerm script, when we are already using
dh_systemd_start in out debian/rules file:

==============
override_dh_systemd_start:
	# Due to https://github.com/systemd/systemd/issues/8102
	# debhelper supporting --remaining like behaviour here would
	# have been useful
	# (Re-)start socket first
	dh_systemd_start snapd.socket
	# Then service
	dh_systemd_start snapd.service
	# Then the rest
	dh_systemd_start $(filter-out snapd.socket snapd.service, $(shell ls debian/snapd/lib/systemd/system/))
==============

wouldn't this rule already cause the units to be stopped at the prerm
step (we are using debhelper compatibility level 9)?

Anyway, I'm soon going to propose a PR, so we can discuss over it.

** Bug watch added: github.com/systemd/systemd/issues #8102
   https://github.com/systemd/systemd/issues/8102

** Changed in: snapd (Ubuntu)
     Assignee: (unassigned) => Alberto Mardegan (mardy)

** Changed in: snapd (Ubuntu)
   Importance: Undecided => High

** Changed in: snapd (Ubuntu)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1969162

Title:
  bad interaction between snapd and update-notifier when snapd package
  is being upgraded

Status in snapd package in Ubuntu:
  In Progress
Status in update-notifier package in Ubuntu:
  New

Bug description:
  On a release upgrade from impish to jammy, I noticed that the dbus
  postinst hung for 10 minutes.  It hung trying to make two calls to
  canonical-livepatch via /usr/share/update-notifier/notify-reboot-
  required: first a call to /snap/bin/canonical-livepatch kernel-
  upgrade-required which hung for ~5 minutes, then a call to
  /snap/bin/canonical-livepatch status which hung for another ~5
  minutes.

  An strace of the second process showed that canonical-livepatch was
  looping trying to connect to /run/snapd.socket:

  [pid 769177] connect(3, {sa_family=AF_UNIX,
  sun_path="/run/snapd.socket"}, 20) = -1 ECONNREFUSED (Connection
  refused)

  This was not attached to anything, because the snapd package was among
  those in the current apt transaction, and was currently not in a
  configured state:

  root      756701  0.0  0.0  24144 12556 pts/20   Ss+  17:26   0:00  |
  |               \_ /usr/bin/dpkg --force-overwrite --status-fd 57
  --no-triggers --configure apparmor:amd64 openssl:amd64 ca-
  certificates:all libmd0:amd64 libmd0:i386 libbsd0:amd64 libbsd0:i386
  libedit2:amd64 libtinfo6:i386 libedit2:i386 libcbor0.8:amd64
  libfido2-1:amd64 libkrb5support0:amd64 libkrb5-3:amd64 libgssapi-
  krb5-2:amd64 openssh-client:amd64 liblzo2-2:amd64 squashfs-tools:amd64
  libcap2:amd64 libkmod2:amd64 udev:amd64 libapparmor1:amd64
  libapparmor1:i386 libdbus-1-3:amd64 libcap2:i386 libzstd1:i386
  libsystemd0:i386 libdbus-1-3:i386 dbus:amd64 libpam-systemd:amd64
  dbus-user-session:amd64 snapd:amd64

  iU  snapd          2.55.3+22.04 amd64        Daemon and tooling that
  enable snap packages

  This should probably be fixed by not stopping snapd in the prerm
  (dh_systemd_start --restart-after-upgrade).

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