[Bug 1824088] Re: unattended upgrade ran one day after schedule

[Magnus Jonsson]

This IS related to daylight saving.

The script: /usr/lib/apt/apt.systemd.daily check that the script is not
run twice at the same period.

The script checks the date of today and the date of the last timestamp to determine the the diff.
The interval is calculated using the number of seconds per day multiplied by number of days.

If a day in the interval has less then 24h this check fails.

This also affects the apt-daily.service that updates.

This is not only Xenial but all the way up to 20.04/Focal.

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Title:
  unattended upgrade ran one day after schedule

Status in apt package in Ubuntu:
  New

Bug description:
  I have noticed a strange behaviour in unattended upgrades. The host in
  question is scheduled to run upgrades on Mondays every second week.
  However, this week it ran upgrades on Tuesday instead (2019-04-09).

  This is the first time I’ve noticed this behaviour. I checked the logs
  in /var/log/apt/history.log* and I saw that worked as intended up
  until this week. Upgrades ran as expected on 2019-03-11 and
  2019-03-25, which where both Mondays.

  The schedule was set with the line 'APT::Periodic::Unattended-Upgrade
  "14";' in the file /etc/apt/apt.conf.d/20auto-upgrades.

  Could it be daylight savings time that has caused skewing of the
  schedule?

  The server is located in Sweden and on 2019-03-31 we switched from CET
  to CEST. If the time diff is calculated with hours instead of calendar
  days passed, perhaps the missing hour on 2019-03-31 caused the
  scheduler to believe that on Monday 2019-03-08, two weeks (336 hours)
  had not yet passed.

  
  ADDITIONAL INFO

  Description:    Ubuntu 16.04.6 LTS
  Release:        16.04

  apt:
    Installed: 1.2.29ubuntu0.1
    Candidate: 1.2.31
    Version table:
       1.2.31 500
          500 http://se.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
   *** 1.2.29ubuntu0.1 500
          500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
          100 /var/lib/dpkg/status
       1.2.10ubuntu1 500
          500 http://se.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

  unattended-upgrades:
    Installed: 0.90ubuntu0.10
    Candidate: 0.90ubuntu0.10
    Version table:
   *** 0.90ubuntu0.10 500
          500 http://se.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
          500 http://se.archive.ubuntu.com/ubuntu xenial-updates/main i386 Packages
          500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
          500 http://security.ubuntu.com/ubuntu xenial-security/main i386 Packages
          100 /var/lib/dpkg/status
       0.90 500
          500 http://se.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
          500 http://se.archive.ubuntu.com/ubuntu xenial/main i386 Packages

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: apt 1.2.29ubuntu0.1
  ProcVersionSignature: Ubuntu 4.4.0-142.168-generic 4.4.167
  Uname: Linux 4.4.0-142-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.18
  Architecture: amd64
  Date: Wed Apr 10 09:06:49 2019
  InstallationDate: Installed on 2017-12-28 (467 days ago)
  InstallationMedia: Ubuntu-Server 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
  SourcePackage: apt
  UpgradeStatus: No upgrade log present (probably fresh install)

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