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

[Magnus Jonsson]

The interesting about the code is that it always only treat the
timestamp of the file as "YYYY-MM-DD" and nothing else (this also
includes "now").

The code has functions for allowing the interval to be set down to 1s
but is does not mean anything to the outcome of the script as it always
looks for complete day(s).

I can only guess that the code might have has some old reference where
the script (or an other script) did something else.

As of the output of "date +%s" it is dependent of the timezone when used
with the --date command.

It kind of looks like the "date" is inputed in the local timezone rather
witch will make epoch time drift dependent of TZ.

# Bionic
$ TZ=UTC0 date --date="2020-01-01" +%s
1577836800
$ TZ=CET date --date="2020-01-01" +%s
1577833200

Using "date -u" will also fix this behaviour of date.

$ TZ=UTC date -u --date="2020-01-01" +%s
1577836800
$ TZ=CET date -u --date="2020-01-01" +%s
1577836800

An easy fix for the original problem would be add the "-u" option to the
date commands in the script:

stamp=$(date -u --date="$(date -r "$stamp_file" --iso-8601)" +%s 2>/dev/null)
now=$(date -u --date="$(date --iso-8601)" +%s 2>/dev/null)

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https://bugs.launchpad.net/bugs/1824088

Title:
  unattended upgrade ran one day after schedule

Status in apt package in Ubuntu:
  Triaged

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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