[Bug 1238982] Re: apt-get installs newer version even when older one is explicitly requested

[David Kalnischkies]

This isn't a bug as such, its a design decision acted out.
If not requested otherwise, APT is installing for each package the version with the highest preference. No implicit derivations: This makes it as predictable as it is required for a low-level tool.

If you want mylib version 1 instead of the more preferred version 2,
than YOU have to tell APT explicitly that you want that. That a package
wants another version (even explicitly) isn't more important than what
the user wants (even if implicitly).

Note by the way that downgrading packages as suggested in the
stackoverflow answer is NOT SUPPORTED by Ubuntu/Debian. It will work for
many packages, but APT itself will never suggest a downgrade on its own
– only if the user forces it and in this case it is assumed that the
user actually knows what (s)he is doing as there is a chance that it
will not work (think of maintainerscripts and/or transitions from
conffile format v1 to v2).

** Changed in: apt (Ubuntu)
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1238982

Title:
  apt-get installs newer version even when older one is explicitly
  requested

Status in “apt” package in Ubuntu:
  Invalid

Bug description:
  On Ubuntu 10.04 (with 0.7.25.3ubuntu9.14) and 12.04 (with
  apt-0.8.16~exp12ubuntu10):

  When a package depends on a specific, non-latest version of another package,
  apt-get install fails with the error message
    my_program : Depends: my_program-common (= 57.0.93) but 57.3.102 is to be installed

  This has been mentioned before, e.g.
  http://stackoverflow.com/questions/17999695/debian-package-dependencies-installing-specific-version-not-the-latest
  but nobody thought to file a bug for it.

  Here's a minimal test case with two versions of a library (mylib-1.0
  and mylib-2.0), and an app (myapp-1.0) that depends explicitly on
  mylib-1.0.

  To view the test case, visit
     http://kegel.com/linux/apt-dependency-version-bug

  To reproduce:
    wget http://kegel.com/linux/apt-dependency-version-bug.tgz
    tar -xzvf apt-dependency-version-bug.tgz
    cd apt-dependency-version-bug
    sh demo.sh build
    sh demo.sh install

  This fails with output

  + apt-cache policy myapp mylib
  myapp:
    Installed: (none)
    Candidate: 1.0
    Version table:
       1.0 0
          500 file:/home/dank/mydebs1/ lucid/main Packages
  mylib:
    Installed: (none)
    Candidate: 2.0
    Version table:
       2.0 0
          500 file:/home/dank/mydebs2/ lucid/main Packages
       1.0 0
          500 file:/home/dank/mydebs1/ lucid/main Packages
  + sudo apt-get install myapp
  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  Some packages could not be installed. This may mean that you have
  requested an impossible situation or if you are using the unstable
  distribution that some required packages have not yet been created
  or been moved out of Incoming.
  The following information may help to resolve the situation:

  The following packages have unmet dependencies:
    myapp: Depends: mylib (= 1.0) but 2.0 is to be installed
  E: Broken packages

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