[Bug 2009871] Re: snapcraft images contain backports repo by default

[Simon Poirier]

** Description changed:

+ [ Impact ]
+ 
+  * buildd images historically pinned backports at 500, thus installing
+    available backports. This is undesirable when using a buildd image
+    to build non-backport (e.g. snapcraft).
+ 
+ [ Test Plan ]
+ 
+  * `apt-cache policy` from within a buildd VM should return the default
+    low (100) priority for backports suites (where InRelease is set to
+    NotAutomatic).
+ 
+ [ Where problems could occur ]
+ 
+  * Unless there is some unknown build mechanism at play, Lauchpad builds
+    should remain unaffected as launchpad takes care of this itself. See [1].
+ 
+  * Any build using buildd implicitly depending on backports by default
+    will see its default change.
+ 
+ [ Other Info ]
+  
+  * [1] https://git.launchpad.net/launchpad-buildd/commit?id=c2ebcb6752
+    Launchpad buildd handling of backports for reference.
+ 
+ [ Original Description ]
+ 
  It seems some snapcraft images contain the backports repo by default. Verified for current version of snapcraft:core20 at least.
  This causes issues at snapcraft build time, as a new repo config is installed when snapcraft runs which doesn't include backports. [ probably by snapcraft itself ].
  
  There is a bug about it here:
  https://bugs.launchpad.net/snapcraft/+bug/1982420
  
  I thought I would log an issue here too to discuss, as including
  backpacks by default seems like a slightly odd decision, and could even
  be a mistake.
  
  Ideally, /etc/apt/preferences.d/backports would not be included in the
  image setup process at all by default, so backport packages are never
  included by default.  Or, if it's there to help fix an issue, perhaps
  the apt pinning config with lower priority and take care the required
  package installation specifically.
  
- 
  ## Test ##
  
  multipass launch -n test-20 -d 10g snapcraft:core20
  
  root at test-20:~# dpkg -l |grep devmapper
  ii  libdevmapper1.02.1:amd64       2:1.02.175-2ubuntu4~ubuntu20.04.1 amd64        Linux Kernel Device Mapper userspace library
  
  root at test-20:~# apt-get update
  
- root at test-20:~# cat /etc/apt/preferences.d/backports 
+ root at test-20:~# cat /etc/apt/preferences.d/backports
  Package: *
  Pin: release a=*-backports
  Pin-Priority: 500
  
  root at test-20:~# apt-cache policy libdevmapper1.02.1
  libdevmapper1.02.1:
-   Installed: 2:1.02.175-2ubuntu4~ubuntu20.04.1
-   Candidate: 2:1.02.175-2ubuntu4~ubuntu20.04.1
-   Version table:
-  *** 2:1.02.175-2ubuntu4~ubuntu20.04.1 500
-         500 http://archive.ubuntu.com/ubuntu focal-backports/main amd64 Packages
-         100 /var/lib/dpkg/status
-      2:1.02.167-1ubuntu1 500
-         500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
- 
- 
+   Installed: 2:1.02.175-2ubuntu4~ubuntu20.04.1
+   Candidate: 2:1.02.175-2ubuntu4~ubuntu20.04.1
+   Version table:
+  *** 2:1.02.175-2ubuntu4~ubuntu20.04.1 500
+         500 http://archive.ubuntu.com/ubuntu focal-backports/main amd64 Packages
+         100 /var/lib/dpkg/status
+      2:1.02.167-1ubuntu1 500
+         500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
  
  Cheers,
  Just

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https://bugs.launchpad.net/bugs/2009871

Title:
  snapcraft images contain backports repo by default

Status in cloud-images:
  New
Status in livecd-rootfs package in Ubuntu:
  New

Bug description:
  [ Impact ]

   * buildd images historically pinned backports at 500, thus installing
     available backports. This is undesirable when using a buildd image
     to build non-backport (e.g. snapcraft).

  [ Test Plan ]

   * `apt-cache policy` from within a buildd VM should return the default
     low (100) priority for backports suites (where InRelease is set to
     NotAutomatic).

  [ Where problems could occur ]

   * Unless there is some unknown build mechanism at play, Lauchpad builds
     should remain unaffected as launchpad takes care of this itself. See [1].

   * Any build using buildd implicitly depending on backports by default
     will see its default change.

  [ Other Info ]
   
   * [1] https://git.launchpad.net/launchpad-buildd/commit?id=c2ebcb6752
     Launchpad buildd handling of backports for reference.

  [ Original Description ]

  It seems some snapcraft images contain the backports repo by default. Verified for current version of snapcraft:core20 at least.
  This causes issues at snapcraft build time, as a new repo config is installed when snapcraft runs which doesn't include backports. [ probably by snapcraft itself ].

  There is a bug about it here:
  https://bugs.launchpad.net/snapcraft/+bug/1982420

  I thought I would log an issue here too to discuss, as including
  backpacks by default seems like a slightly odd decision, and could
  even be a mistake.

  Ideally, /etc/apt/preferences.d/backports would not be included in the
  image setup process at all by default, so backport packages are never
  included by default.  Or, if it's there to help fix an issue, perhaps
  the apt pinning config with lower priority and take care the required
  package installation specifically.

  ## Test ##

  multipass launch -n test-20 -d 10g snapcraft:core20

  root at test-20:~# dpkg -l |grep devmapper
  ii  libdevmapper1.02.1:amd64       2:1.02.175-2ubuntu4~ubuntu20.04.1 amd64        Linux Kernel Device Mapper userspace library

  root at test-20:~# apt-get update

  root at test-20:~# cat /etc/apt/preferences.d/backports
  Package: *
  Pin: release a=*-backports
  Pin-Priority: 500

  root at test-20:~# apt-cache policy libdevmapper1.02.1
  libdevmapper1.02.1:
    Installed: 2:1.02.175-2ubuntu4~ubuntu20.04.1
    Candidate: 2:1.02.175-2ubuntu4~ubuntu20.04.1
    Version table:
   *** 2:1.02.175-2ubuntu4~ubuntu20.04.1 500
          500 http://archive.ubuntu.com/ubuntu focal-backports/main amd64 Packages
          100 /var/lib/dpkg/status
       2:1.02.167-1ubuntu1 500
          500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages

  Cheers,
  Just

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