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[Steve Langasek <1888575@xxxxxxxxxxxxxxxxxx>]

** Changed in: livecd-rootfs (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1888575

Title:
  Split motd-news config into a new package

Status in base-files package in Ubuntu:
  Fix Released
Status in livecd-rootfs package in Ubuntu:
  Invalid
Status in ubuntu-meta package in Ubuntu:
  Fix Released
Status in base-files source package in Xenial:
  Fix Released
Status in livecd-rootfs source package in Xenial:
  Fix Released
Status in ubuntu-meta source package in Xenial:
  Fix Released
Status in base-files source package in Bionic:
  Fix Released
Status in livecd-rootfs source package in Bionic:
  Invalid
Status in ubuntu-meta source package in Bionic:
  Fix Released
Status in base-files source package in Focal:
  Fix Released
Status in livecd-rootfs source package in Focal:
  Invalid
Status in ubuntu-meta source package in Focal:
  Fix Released
Status in base-files source package in Groovy:
  Fix Released
Status in livecd-rootfs source package in Groovy:
  Invalid
Status in ubuntu-meta source package in Groovy:
  Fix Released

Bug description:
  [Impact]
  The motd-news script is largely useless for desktop users, as they rarely login via a text console. It makes more sense for server users.

  We can use package dependencies to have the motd-news script enabled on servers, but disabled on desktops, and still handle upgrades. This is the plan:
  - move /etc/default/motd-news from base-files into a new binary package (motd-news-config, produced by src:base-files)
  - have ubuntu-server depend on motd-news-config
  - have base-files break current ubuntu-server, so that if base-files if upgraded and ubuntu-server is installed, ubuntu-server will also be upgraded to the new version which has the depends on motd-news-config

  Care must be taken to preserve a changed /etc/default/motd-news when
  the upgrade installs the new motd-news-config package. For example, on
  a server that has set ENABLED=0 in /etc/default/motd-news and upgrades
  to the new base-files and ubuntu-server, and gets the new motd-config-
  news package, ENABLED=0 must remain set.

  [Test Case]
  a) base-files installed, ubuntu-server installed, unmodified /e/d/motd-news
  apt install base-files
  - upgrades ubuntu-server
  - installs motd-news-config
  - /e/d/motd-news remains, motd-news remains enabled

  b) base-files installed, ubuntu-server installed, modified /e/d/motd-news
  apt install base-files
  - upgrades ubuntu-server
  - installs motd-news-config
  - /e/d/motd-news remains with the original modification

  c) base-files installed, ubuntu-server not installed, unmodified /e/d/motd-news
  apt install base-files
  - upgrades base-files
  - removes /e/d/motd-news
  - motd-news is disabled

  d) base-files installed, ubuntu-server not installed, modified /e/d/motd-news
  apt install base-files
  - upgrades base-files
  - /e/d/motd-news gets renamed to backup
  - motd-news is disabled

  e) removing motd-news-config will also remove ubuntu-server (since
  it's a depends, and not a recommends)

  f) upgrading just ubuntu-server should pull motd-news-config in, and
  force-upgrade base-files

  g) Removing motd-news-server leaves /e/d/motd-news around; purging
  motd-news-server removes the /e/d/motd-news config file

  h) base-files installed, ubuntu-server installed, removed /e/d/motd-news
  - apt install base-files
  - upgrades base-files, upgrades ubuntu-server, installs motd-news-config
  - /e/d/motd-news is installed with ENABLED=0

  i) base-files installed, ubuntu-server NOT installed, removed e/d/motd-news
  - apt install base-files
  - base-files is upgraded
  - no /e/d/motd-news is installed, motd-news remains disabled

  j) Perform a release upgrade from the previous ubuntu release to the
  one being tested while having ubuntu-server NOT installed (or use a
  desktop install). At the end, motd-news should be disabled. Verify
  with:

  $ sudo /etc/update-motd.d/50-motd-news --force
  $ (no output)

  k) Test that supporting changes for xenial are in place:

    i) verify grub-legacy-ec2 is not in the xenial server seed
    ii) verify that the rootfs manifest built from the ubuntu-cpc project contains the ubuntu-server package
    iii) verify that images built from the ubuntu-cpc project which purge grub-legacy-ec2 have retained ubuntu-server
    iv) verify that the base ubuntu-cpc image continues to have grub-legacy-ec2 installed.

  [Regression Potential]
  This update is about config file ownership transfer: /e/d/motd-news belonged to base-files, now it belongs to motd-news-config. We tried to handle two important cases here:
  a) /e/d/motd-news config was changed while it belonged to base-files. For example, an user could have set ENABLED=0. We need to transfer that change to the motd-news-config package when it is installed, otherwise this SRU would jsut re-enabled motd-news. This is handled in d/motd-news-config.postinst's configure case.

  b) /e/d/motd-news config file was *removed* while it belonged to base-files. In such a case, a normal upgrade of the package (base-files in this example) would not reinstate the file. Much less this upgrade here, which has an explicit rm_conffile maintscript-helper for it. But the motd-news-config package that could be installed in the transaction would place the default config file back, and the default is ENABLED=1. Thus, a system that had motd-news disabled via removing the config file would now have it re-enabled after the upgrade.
  This was trickier to handle, and we do it in base-files's postinst and motd-news-config's  postinst. The drawback is that in one scenario, where just base-files is upgraded and /e/d/motd-news was manually removed by the user, there will be a /e/d/motd-news.wasremoved leftover empty file (see "other info" below for details).

  In general, the regression risks here are:
  - have motd-news enabled again on a system where it was previously disabled. We tried to envision two ways it would have been disabled (set ENABLED=0, and remove the config file). There are probably others
  - differences in dpkg and/or debhelper behavior in older ubuntu releases leading to unexpected results (should be covered by the test cases from this SRU)
  - xenial in particular is trickier, because src:base-files there does NOT use debhelper, so many of the things we take for granted have to be done by hand
  - have some sort of dpkg postinst or dependency error because of unpredicted scenarios. Certain assumptions are being made, like the renames that dpkg-maintscript-helper does, and that the filename /etc/default/motd-news.wasremoved that I'm touching and verifying is really mine and not something that was there already.
  - the versions I'm breaking/replacing on, and using rm_conffiles on, must be exact. These are the versions today in the archive (2020-08-12):

  base-files:
  x: 9.4ubuntu4.12
  b: 10.1ubuntu2.9
  f: 11ubuntu5.1
  g: 11ubuntu12 (was 11ubuntu10)

  ubuntu-meta:
  x: 1.361.4
  b: 1.417.4
  f: 1.450.1
  g: 1.452

  Which reflect in these relationships in the updated packages:
  Groovy:
  ubuntu-server 1.453:
    Depends: motd-news-config
  base-files 11ubuntu11:
    Breaks: ubuntu-server (<< 1.453)
    rm_conffile /etc/default/motd-news 11ubuntu11~ base-files
  motd-news-config 11ubuntu11:
    Breaks/Replaces: base-files (<< 11ubuntu11)

  Focal:
  ubuntu-server 1.450.2:
    Depends: motd-news-config
  base-files 11ubuntu5.2:
    Breaks: ubuntu-server (<< 1.450.2)
    rm_conffile /etc/default/motd-news 11ubuntu5.2~ base-files
  motd-news-config 11ubuntu5.2:
    Breaks/Replaces: base-files (<< 11ubuntu5.2)

  Bionic:
  ubuntu-server 1.417.5:
    Depends: motd-news-config
  base-files 10.1ubuntu2.10:
    Breaks: ubuntu-server (<< 1.417.5)
    rm_conffile /etc/default/motd-news 10.1ubuntu2.10~ base-files
  motd-news-config 10.1ubuntu2.10:
    Breaks/Replaces: base-files (<< 10.1ubuntu2.10)

  Xenial:
  ubuntu-server 1.361.5:
    Depends: motd-news-config
  base-files 9.4ubuntu4.13:
    Breaks: ubuntu-server (<< 1.361.5)
    rm_conffile /etc/default/motd-news 9.4ubuntu4.13~ base-files
  motd-news-config 9.4ubuntu4.13:
    Breaks/Replaces: base-files (<< 9.4ubuntu4.13)

  [Other Info]
  a) Testcase (i) will leave around an empty /etc/default/motd-news.wasremoved file, created by the base-files postinst. This file is removed by the motd-news-config postinst, but since that package doesn't get installed in that particular scenario, the file remains. I toyed with the idea of adding an extra check to base-file's postinst, like this:
  --- a/debian/postinst.in
  +++ b/debian/postinst.in
  @@ -133,7 +133,11 @@ motd_news_config="/etc/default/motd-news"
   if [ ! -e ${motd_news_config} ]; then
     if [ ! -e ${motd_news_config}.dpkg-remove ]; then
       if [ ! -e ${motd_news_config}.dpkg-backup ]; then
  -      touch ${motd_news_config}.wasremoved
  +      # The .wasremoved file only matters if ubuntu-server is installed,
  +      # because that's what will pull in motd-news-config
  +      if dpkg -l ubuntu-server 2>/dev/null | grep -q ^i; then
  +        touch ${motd_news_config}.wasremoved
  +      fi
       fi
     fi
   fi

  But deemed it too risky, and not worth further potential regressions.
  It seemed to work, though, at least for groovy.

  b) Currently the xenial cloud images, with the exception of the AWS
  one, do not have ubuntu-server installed. This means that this SRU
  will disable motd-news on them, unless ubuntu-server was manually
  installed for some reason. This includes LXD xenial images as well.

  c) The new motd-news-config package has its d/control priority set to
  "optional", so a release upgrade won't pick it up (presumably the same
  applies to the installer). I've been told there are archive overrides
  that might need updating as well: dear SRU team member, please check,
  or ask an archive admin to check.

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