[Bug 1732026] Re: update-manager creates duplicate snapper "pre" snapshots

[R1dO]

I believe it is a bit premature to mark this as invalid, due to an
external (non ubuntu) website telling 17.04 has reached end-of life.

Even though the bug report might have surfaced in 17.04, there has not
been any information mentioning it is fixed in more recent ubuntu (or
update-manager) versions.

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https://bugs.launchpad.net/bugs/1732026

Title:
  update-manager creates duplicate snapper "pre" snapshots

Status in update-manager package in Ubuntu:
  New

Bug description:
  This system uses a btrfs filesystem in combination with snapper.

  Via the file ``/etc/apt/apt.conf.d/80snapper`` (default file from
  repositories) it is configured to take pre-post snapshots upon
  performing any apt driven changes.

  When using the update-manager i noticed 2 pre-snapshots are created at
  approximately the same time when upgrading. Leading to a snapper
  warning ``THROW: illegal snapshot`` for post upgrade actions.

  In order to rule out ``snapper`` or ``apt`` as a source i tested the
  other methods (known to me) for upgrading packages, none of them
  showing the error (see table below):

  ================ | ==================
  Case             | # of pre snapshots
  ================ | ==================
  Synaptic updates | 1
  Update Manager   | 2 <-
  apt upgrade      | 1
  apt-get upgrade  | 1
  ================ | ==================

  I suspect the upgrade-manager makes 2 DPkg::Pre-Invoke calls when this
  happens. But i'm too unfamiliar with this package to do any real bug
  hunting.

  ProblemType: Bug
  DistroRelease: Ubuntu 17.04
  Package: update-manager 1:17.04.8
  ProcVersionSignature: Ubuntu 4.10.0-38.42-generic 4.10.17
  Uname: Linux 4.10.0-38-generic x86_64
  ApportVersion: 2.20.4-0ubuntu4.5
  Architecture: amd64
  CurrentDesktop: XFCE
  Date: Mon Nov 13 22:41:48 2017
  GsettingsChanges:
   b'com.ubuntu.update-manager' b'show-details' b'true'
   b'com.ubuntu.update-manager' b'window-height' b'1390'
   b'com.ubuntu.update-manager' b'first-run' b'false'
   b'com.ubuntu.update-manager' b'window-width' b'2560'
   b'com.ubuntu.update-manager' b'launch-time' b'int64 1510607283'
  InstallationDate: Installed on 2016-12-21 (327 days ago)
  InstallationMedia: Xubuntu 16.10 "Yakkety Yak" - Release amd64 (20161012.2)
  PackageArchitecture: all
  SourcePackage: update-manager
  UpgradeStatus: Upgraded to zesty on 2017-04-16 (211 days ago)

  p.s. edited the table to have a visual separation of the columns

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