** Description changed:
[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
[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: 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.
+ 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.
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https://bugs.launchpad.net/bugs/1888575
Title:
Split motd-news config into a new package
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