On Saturday 02 May 2015 16:36:30 Christian Seiler wrote: > On 05/02/2015 05:06 PM, Lisi Reisz wrote: > > Does the "-t wheezy-backports" format only work with backports? > > No, it works here as well. From the manpage of apt-get: > > This option controls the default input to the policy engine; it > > creates a default pin at priority 990 using the specified release > > string. > > This means that ALL packages from that suit will get 990 priority (which > is really high, see the apt_preferences(5) manpage). This has the > consequence that if you do that for experimental, ALL dependencies of a > package will then also come from experimental (because -t affects the > WHOLE apt-get run, not just a single package). For backports it's > generally OK, but for other things such as running testing with 1 or 2 > packages from experimental, it can be very problematic. > > To give you an example of the consequences: > > - package libA is version 1 in stable, version 2~bpo in > stable-backports. > - package libD is version 10 in stable and version 11~bpo in > stable-backports > - package B is version 23 in stable and version 24~bpo in > stable-backports > - both versions require libA in any version >= 1 > - version 24~bpo additionally requires libD >= 11~bpo > (version 23 didn't require libD at all) > - package C is version 42 in stable and version 50~bpo in > stable-backports > - version 42 requires libA with version >= 1 > - version 50~bpo requires libA with version >= 2~bpo > > If you now just want to install package B from backports (but are > uninterested in C), and neither of the four packages mentioned is > installed yet, you can do that in two ways: > > 1. pin D from backports to priority 500, then try to install it, APT > will complain about libD not being installed in the correct version, > you then pin libD from backports to priority 500 and then you can > install the package > > => libD and B will be from backports > => libA is still from stable, because B doesn't require a newer > version > > 2. apt-get install -t stable-backports B > > => both libA and libD will also be taken from backports > > Now with backports this is typically fine (because the aforementioned > case is also very rare when it comes to backports, and even if it does > happen, libraries in backports are typically not that prone to causing > problems), but for experimental - or worse yet, other repositories, this > can be something you really, really don't want. > > (Doesn't have to be libraries btw., can be any dependency.) > > Therefore: use apt-get install -t with great care. It's probably fine > for backports, but don't use it for anything else unless you REALLY know > what you are doing.
Thanks again, Christian. That is really helpful and lucid. I have always had trouble getting my head round pinning, for some reason. Not the concepts, but actually doing it. Thanks to you today, light has dawned. I'm very grateful. Lisi -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/201505021644.29372.lisi.re...@gmail.com
