dpkg keeps diversions for removed packages

sorry, but dpkg-divert only does what it's told here. This screen-profiles package was responsible for removing /usr/bin/screen on package removal; nothing dpkg can do when a package decides to leave one around. Reassigning to byobu which provided screen-profiles.

So, it seems that this was caused by an incorrect fix for 390808 in byobu:

  * debian/postinst, debian/screen-profiles.postinst: ensure that
    /usr/bin/screen doesn't disappear, which causes the dpkg-divert
    removal to fail; LP: #390808

But just the opposite is true. dpkg-divert fails *if* /usr/bin/screen exists, not if it doesn't.

root@sphinx:~# dpkg-divert --package screen-profiles --rename --remove /usr/bin/screen
Removing `diversion of /usr/bin/screen to /usr/bin/screen.real by screen-profiles'
dpkg-divert: rename involves overwriting `/usr/bin/screen' with
  different file `/usr/bin/screen.real', not allowed

It seems to me that the real cause of 390808 is that the wrong package name was used to remove the diversion:

> dpkg-divert: mismatch on package when removing `diversion of /usr/bin/screen by byobu'
> found `diversion of /usr/bin/screen to /usr/bin/screen.real by screen-profiles'

Okay, I thought I had fixed this correctly before, with the sunsetting of the screen-profiles package.

Evidently that was wrong.

Can someone clearly explain to me what needs to be done in byobu at this point to fix this? Do I need to resurrect a screen-profiles binary package to force the dpkg-divert update?

Since dpkg-divert takes a package name as an arg, you should not need the other binary package. I don't know what policy/lintian say about dpkg-divert invocations though.

First, remove this from the postinst:

# The target of the diversion somehow disappeared which will cause
# the divert removal to fail; we don't want that to happen
[ -e "/usr/bin/screen.real" ] && [ ! -e "/usr/bin/screen" ] && cp -a /usr/bin/screen.real /usr/bin/screen

I think the following script fragment (with an appropriate version test maybe?) will clean this situation up:

if [ -f /usr/bin/screen ] && [ -f /usr/bin/screen.real ]; then
  divertpkg=$(dpkg-divert --listpackage /usr/bin/screen)
  if [ "$divertpkg" = "screen-profiles" ]; then
     rm /usr/bin/screen
     dpkg-divert --package screen-profiles --rename --remove /usr/bin/screen
  fi
fi

This is how I re-created the situation to test. I don't know if it covers all the possible situations that machines can be in.

dpkg-divert --package screen-profiles --add --divert /usr/bin/screen.real --rename /usr/bin/screen
cp -a /usr/bin/screen.real /usr/bin/screen

> I don't know what policy/lintian say about dpkg-divert invocations though.

Policy has no problem; lintian stands no more chance of grokking dpkg-divert invocations than developers do. :P

> This is how I re-created the situation to test. I don't know if it covers
> all the possible situations that machines can be in.

There may be other cases not handled, but I can confirm that your proposed fix for this issue is logically correct (including the rm /usr/bin/screen).

Thank you very much Chaskiel! And you, Steve for the review.

I'll try to squeeze this into Natty, as I think this is an important fix for an annoying issue that creeps up from time to time.

This bug was fixed in the package byobu - 3.30-0ubuntu1

---------------
byobu (3.30-0ubuntu1) natty; urgency=low

  [ Dustin Kirkland ]
  * usr/share/applications/byobu.desktop: fix description
  * usr/bin/byobu-status-detail: make a couple of minor modifications
    noticed while investigating the already-fixed LP: #750887
  * usr/lib/byobu/raid: fix grep that changed recently in Linux's
    md driver's printing to /proc/mdstat, LP: #760693
  * usr/share/byobu/profiles/common: preserve splits across detach/reattach,
    LP: #760696
  * usr/bin/byobu-launcher: don't disrupt work flow, but rather inform
    user about launching byobu in a nested screen session, LP: #747649
  * usr/bin/byobu-launch, usr/bin/byobu-launcher-install: fix handling
    of logout behavior, when dpkg-configured globally by the sysadmin,
    LP: #741281
  * usr/share/byobu/profiles/common: fix bold color intensity, LP: #727466
  * usr/bin/byobu-janitor, usr/bin/byobu-launch, usr/bin/byobu-launcher-
    install, usr/bin/byobu-launcher-uninstall,
    usr/share/byobu/keybindings/f-keys,
    usr/share/byobu/keybindings/screen-escape-keys,
    usr/share/man/man1/byobu.1:
    - add a more permanent fix for LP: #604931
    - update documentation
  * usr/share/byobu/keybindings/f-keys,
    usr/share/byobu/keybindings/screen-escape-keys:
    - fix ctrl-f5
  * debian/source/format, === removed directory debian/source: remove these
    until bzr builddeb bug gets fixed
  * usr/bin/byobu, usr/share/byobu/profiles/byoburc,
    usr/share/byobu/profiles/Makefile.am,
    usr/share/byobu/profiles/screenrc: support using ~/.byoburc, instead of
    ~/.screenrc, if present; some users seem to want to use byobu and screen
    separately, and keep their profiles separate, LP: #731529
  * usr/bin/byobu-janitor: use greadlink on Mac OSX, LP: #740370
  * usr/bin/byobu-select-session: fix broken path to screen, affects users
    who build/install byobu locally only, LP: #758177

  [ Chaskiel Grundman ]
  * debian/postinst: correctly fix old-school screen-profiles era diversions
    of /usr/bin/screen, LP: #727738
 -- Dustin Kirkland <email address hidden> Sun, 27 Feb 2011 10:29:53 -0600