Open Build Service

Fighting the Linux binary distribution problem..

Created by Andreas Baumann

http://www.andreasbaumann.cc/slide/obs

(C)2015

The Linux Binary Distribution Disaster

Linus Torvalds: Provides MacX and Windows binaries for his divelog application but no Linux binaries, why?

There are no Linux binaries: there are Fedora binaries, Ubuntu binaries, ArchLinux binaries, etc..

Linux binaries differ..

  • ..in package formats (deb, rpm, tgz, ...)
  • ..in build rules (compiler flags, fencing, optimization, ...)
  • Linux Standard Base (LSB): should actually guarantee ABI and API stability..
  • The problem is, there is still too much variation..

Shared libraries

  • share common code on a platform, good idea
  • there is not a common view of what can be shared and should be shared
  • packet names and versions differ
  • sometimes compilation flags differ (e.g. no threading support in sqlite3 on RHEL5)

Distribution types

  • Frozen releases, e.g. Debian 8, RHEL 7, Ubuntu LTS, ..., long release cycles (4-8 years), they are stable, but only if you use very old software
  • Rolling releases, e.g. Fedora, ArchLinux, Gentoo, ... You have the newest and shiniest software, but stability may suffer, backporting to other distros gets almost impossible.

Options for software developers

Islands, part 1

  • Create your own universe: examples Java, Go, Python, ...
  • You deploy your software as a blob of static libraries, there might be sharing inside your universe but not between universes.
  • In C++ we are "stuck" to the ELF format, shared libarires, binaries in distribution packages. Build on one Linux (which one?) and hope it runs everywhere
  • Local libraries must be maintained (security patches), imagine a bundled, unpatched, 5 years old libssl. :-)

Package meta-systems

Islands, part 2

  • http://www.openpkg.org/: cross-platform RPMs
  • BSD-like port systems (gentoo, netsrc, etc.): but this means going back to distribution of source code only

Package build systems

Islands, part 3

Package build systems

Islands, part 3

  • Linux distros try to maintain their bleeding edge product with the help of the community.
  • Naturally communities form islands
  • Exception: OpenBuild system, they build SuSE, RHEL, Debian, Ubuntu, Mandriva, Arch,..
  • This "behaviour" should be honoured and supported as it is the really only way to go right now

OBS

  • Basically having one RPM SPEC-file and one Debian/Ubuntu tree covers the majority of Linux distributions
  • Choose your dependencies wisely and provide what's not available on old distros on your own.
  • Either bundle your stub packages with your software package or package them into a 3rdParty meta package
  • Make sure package names DON'T collide!

Automatization

  • Combine it with github, build the source trees there (git tag)
  • Webhooks draw the tarballs and spec files to the OBS cluster
  • Publish releases on a web space
  • Keep the current git master as rolling last release of your software

Current process

  • Update in CMakeLists.txt:
    
    set( STRUS_MAJOR_VERSION 0 )
    set( STRUS_MINOR_VERSION 2 )
    set( STRUS_PATCH_VERSION 1 )
                                
  • Adapt %changelog and dist/debian/changelog. Keep STRICTLY to syntax! For tipps see also: http://keepachangelog.com/
  • Commit the master revision and tag it
  • 
    git commit -a -m 'changed to release 0.2.1'
    git tag 0.2.1
                                                            

Current process

  • Deploy to OBS workspace:
    
    osc co home:PatrickFrey (into $HOME/home:PatrickFrey)
  • 
    cmake .
    dist/obs/deploy_to_obs.sh
                                
  • Remove source tarballs of old release, add tarballs of new release:
    
    cd home:PatrickFrey/strus
    osc up
    osc rm strus-0.1.6*
    osc add strus-0.2.1*
    osc commit -m 'added version 0.2.1'
                                                            

Issues

  • dist/obs/deploy_to_obs.sh should be eliminated
  • Release versions need patching, the mirroring system plays mean tricks otherwise..
  • How to automatically update the OSC workspace, not having tarballs there, etc.
  • Have a central changelogs, create Debian and RHEL style from it
  • git commit is always needed, otherwise tarball lacks modified/added artifacts
  • Don't change git tags later on! Rather revoke broken releases.

Local OSB builds

  • Build locally in a chrooted envorinment:
    
    cd home:PatrickFrey/strus
    osc build --noinit Debian_8.0 x86_64 strus.dsc
    osc build --noinit xUbuntu_12.04 x86_64 strus-xUbuntu_12.04.dsc 
    osc build --noinit CentOS_5 i586 strus.spec
                                
  • Access a shell in the chroot to investigate issues:
  • 
    sudo chroot /var/tmp/build-root/xUbuntu_12.04-x86_64/ /bin/bash --login
    cat /etc/debian_version 
    wheezy/sid
                                

Local OSB builds

  • The artifacts of the build system are somewhat hidden in the chroot:
  • 
    /usr/src/packages/BUILD/
    /home/abuild/rpmbuild/BUILD/strus-0.2.1
    /usr/src/packages/BUILD/strus-0.2.1
                                
  • The chrooted environment lacks things like an editor or a debugger or even a package manager inside the chroot. Either add a dependency for them 'BuildRequires:' or use the package manager from outside the chroot (works nice on Archlinux and for Ubuntu on Ubuntu, 'apt-get' on RHEL might be a problem).

Links