Permanently block distro package installation?

Question

I'm using a package provided in a PPA on Ubuntu. I use the PPA version because Debian's version is anemic to the point its effectively broken.

Today, when I went through the cycle of apt-get update and apt=get dist-upgrade, I was presented with:

$ sudo apt-get dist-upgrade 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
The following NEW packages will be installed:
  binutils-arm-none-eabi libnewlib-arm-none-eabi libnewlib-dev
The following packages will be upgraded:
  gcc-arm-none-eabi libcurl3 libcurl3-gnutls
3 upgraded, 3 newly installed, 0 to remove and 0 not upgraded.
Need to get 338 kB/24.7 MB of archives.
After this operation, 9,572 kB disk space will be freed.

dist-upgrade is trying to install the packages that caused me the trouble in the past: binutils-arm-none-eabi and gcc-arm-none-eabi. Even a standard upgrade tries to install some of the same packages that caused me trouble.

I want to permanently block the distro's packages for binutils-arm-none-eabi and gcc-arm-none-eabi. How does one Permanently block a distro package, but allow a PPA that provides the same package?

Answer 1

In APT, you "pin" packages – i.e. specify custom package preferences based on various properties.

First run apt-cache policy to see properties of configured repositories, and look for one that is specific to your PPA. It'll probably have something like release n=precise (based on the Ubuntu release it targets) or at least origin launchpad.net (based on the source site):

$ apt-cache policy | egrep -i "(ppa|arm)"
 500 http://ppa.launchpad.net/terry.guo/gcc-arm-embedded/ubuntu/ trusty/main i386 Packages
     release v=14.04,o=LP-PPA-terry.guo-gcc-arm-embedded,a=trusty,n=trusty,l=GNU ARM Embedded Toolchain,c=main
     origin ppa.launchpad.net
 500 http://ppa.launchpad.net/terry.guo/gcc-arm-embedded/ubuntu/ trusty/main amd64 Packages
     release v=14.04,o=LP-PPA-terry.guo-gcc-arm-embedded,a=trusty,n=trusty,l=GNU ARM Embedded Toolchain,c=main
     origin ppa.launchpad.net
     release v=14.04,o=LP-PPA-app-review-board,a=trusty,n=trusty,l=Application Review Board PPA,c=main
     release v=14.04,o=LP-PPA-app-review-board,a=trusty,n=trusty,l=Application Review Board PPA,c=main

Then create a file /etc/apt/preferences:

Package: binutils-arm-none-eabi
Pin: origin ppa.launchpad.net
Pin-Priority: 900

Package: gcc-arm-none-eabi
Pin: origin ppa.launchpad.net
Pin-Priority: 900

For Pin, use the repository property you found earlier. For the priority, choose a number that's higher than any of the regular Debian repositories.

Finally, run apt-cache policy binutils-arm-none-eabi – this time with the package name – to verify that the preferences are correctly applied:

$ apt-cache policy gcc-arm-none-eabi
gcc-arm-none-eabi:
  Installed: 4-8-2014q2-0trusty10
  Candidate: 4-8-2014q2-0trusty10
  Package pin: 4-8-2014q2-0trusty10
  Version table:
     4.8.2-14ubuntu1+6 900
        500 http://us.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
 *** 4-8-2014q2-0trusty10 900
        500 http://ppa.launchpad.net/terry.guo/gcc-arm-embedded/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status

• AptPreferences on Debian Wiki
• PinningHowto on Ubuntu Wiki
• Apt-Pinning for Beginners