[Bug 1978125] Re: apt ignoring pin/block/hold files in preferences.d for snapd

Thu Jun 30 13:48:58 UTC 2022

** Description changed:

- Did some upgrades on a new box on 22.04, and had previously removed
- snapd and BLOCKED via a file in /etc/apt/preferences.d/
+ [Impact]
+ Negative pins are overridden by a pin of 1 if the package is phasing and "not for us", which suddenly makes packages installable that were effectively blocklisted by the negative pin, overriding user settings
+ 
+ [Test plan]
+ Integration tests covers the fix for this. The fix is not enabled by default as the implementation was changed for bug 1979244, however the new implementation also tests that.
+ 
+ These tests are run during autopkgtest.
+ 
+ To test with the new implementation, create an update that pulls in a
+ phasing package that is pinned -1 and make sure it's not being
+ installed. I did not add a test for that case as the new implementation
+ only works by keeping back packages, so it by definition can't suddenly
+ cause a package to be allowed.
+ 
+ [Where problems could occur]
+ This specific bit is not enabled anymore, but for the sake of it, it is implemented as a ceiling for the pin, so any other pin will be limited to 1 if the package is considered a "not-for-us" phasing package. So problems could occur there.
+ 
+ For the new phasing implementation, see bug 1979244.
+ 
+ [Original bug report]
+ Did some upgrades on a new box on 22.04, and had previously removed snapd and BLOCKED via a file in /etc/apt/preferences.d/

  And this upgrade cycle REINSTALLED snapd! and the stupid FF snap! Had to
  repurge it again!

  I had done this previously, and it appears that apt or something is
  IGNORING any pin/holds of snapd

  I use preferences.d files as using:
- sudo apt-mark hold snapd 
+ sudo apt-mark hold snapd

  This has never worked on any package, ever...

- 
- I have: 
+ I have:
  /etc/apt/preferences.d$ cat snapd

  Package: snapd
  Pin: origin *
  Pin-Priority: -1

  And that previously resulted in an error on apt in any attempt to
  install snapd, including using -s... NOW it will still attempt to
  install snapd!

  I've tried several variants of this as well, which other 22.04 and 20.04
  boxes have, same on 22.04, it will allow snapd install!

  Did sudo apt-get update, apt update several times, rebooted several
  times, had various levels of the Pin-Priority from -1 to -9999, still
  will attempt to install snapd, versus the expected error

  sudo apt-get -s install snapd

  Expected error: Reading package lists... Done Building dependency tree
  Reading state information... Done Package snapd is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source

  E: Package 'snapd' has no installation candidate

  20.04 boxes still seem to fail correctly with this pin file,.....

  Checking my BASE VM IMAGE of 22.04 and this still works there, as its
  not been touched, this pin file blocks snapd from installing as
  expected... this is apt 2.3.15, updated one is 2.4.5....

  If I pick ANY OTHER RANDOM PACKAGE out and use the same pin/block file,
  and change the name to that package, it blocks it from installing!
  Anything but snapd this works for!

  1)$ lsb_release -rd
  Description:    Ubuntu 22.04 LTS
  Release:        22.04

  2)  sudo apt-cache policy apt
  apt:
-   Installed: 2.4.5
-   Candidate: 2.4.5
-   Version table:
-  *** 2.4.5 500
-         500 http://us.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
-         100 /var/lib/dpkg/status
+   Installed: 2.4.5
+   Candidate: 2.4.5
+   Version table:
+  *** 2.4.5 500
+         500 http://us.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
+         100 /var/lib/dpkg/status

  What I expect to happen? HONOR MY BLOCK on snapd! It works for any
  random package chosen, EXCEPT snadp!

** Also affects: apt (Ubuntu Kinetic)
   Importance: Undecided
       Status: Triaged

** Also affects: apt (Ubuntu Impish)
   Importance: Undecided
       Status: New

** Also affects: apt (Ubuntu Jammy)
   Importance: Undecided
       Status: New

** Changed in: apt (Ubuntu Impish)
       Status: New => In Progress

** Changed in: apt (Ubuntu Jammy)
       Status: New => In Progress

** Changed in: apt (Ubuntu Kinetic)
       Status: Triaged => Fix Committed

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https://bugs.launchpad.net/bugs/1978125

Title:
  apt ignoring pin/block/hold files in preferences.d for snapd

Status in apt package in Ubuntu:
  Fix Committed
Status in apt source package in Impish:
  In Progress
Status in apt source package in Jammy:
  In Progress
Status in apt source package in Kinetic:
  Fix Committed

Bug description:
  [Impact]
  Negative pins are overridden by a pin of 1 if the package is phasing and "not for us", which suddenly makes packages installable that were effectively blocklisted by the negative pin, overriding user settings

  [Test plan]
  Integration tests covers the fix for this. The fix is not enabled by default as the implementation was changed for bug 1979244, however the new implementation also tests that.

  These tests are run during autopkgtest.

  To test with the new implementation, create an update that pulls in a
  phasing package that is pinned -1 and make sure it's not being
  installed. I did not add a test for that case as the new
  implementation only works by keeping back packages, so it by
  definition can't suddenly cause a package to be allowed.

  [Where problems could occur]
  This specific bit is not enabled anymore, but for the sake of it, it is implemented as a ceiling for the pin, so any other pin will be limited to 1 if the package is considered a "not-for-us" phasing package. So problems could occur there.

  For the new phasing implementation, see bug 1979244.

  [Original bug report]
  Did some upgrades on a new box on 22.04, and had previously removed snapd and BLOCKED via a file in /etc/apt/preferences.d/

  And this upgrade cycle REINSTALLED snapd! and the stupid FF snap! Had
  to repurge it again!

  I had done this previously, and it appears that apt or something is
  IGNORING any pin/holds of snapd

  I use preferences.d files as using:
  sudo apt-mark hold snapd