Revision b8e39189 doc/design-upgrade.rst
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to install new binaries ahead of time, and the actual switch |
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between versions will be a single command. |
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While changing the file layout anyway, we install the python |
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code, which is architecture independent, under ``${prefix}/share``,
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in a way that properly separates the Ganeti libraries of the |
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various versions. |
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Path changes to allow multiple versions installed |
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------------------------------------------------- |
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These paths will be changed in the following way. |
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- The python package will be installed to ``${pythondir}/ganeti-${VERSION}``.
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Here ${VERSION} is the full qualified version number, consisting of
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major, minor, revision, and suffix. All python executables will be changed |
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to import the correct version of the ganeti package. |
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- The python package will be installed to |
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``${PREFIX}/share/ganeti/${VERSION}/ganeti``.
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Here ${VERSION} is, depending on configure options, either the full qualified
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version number, consisting of major, minor, revision, and suffix, or it is |
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just a major.minor pair. All python executables will be installed under |
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``${PREFIX}/share/ganeti/${VERSION}`` so that they see their respective
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Ganeti library. ``${PREFIX}/share/ganeti/default`` is a symbolic link to
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``${sysconfdir}/ganeti/share`` which, in turn, is a symbolic link to
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``${PREFIX}/share/ganeti/${VERSION}``. For all python executatables (like
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``gnt-cluster``, ``gnt-node``, etc) symbolic links going through |
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``${PREFIX}/share/ganeti/default`` are added under ``${PREFIX}/sbin``.
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- All other files will be installed to the corresponding path under |
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``${libdir}/ganeti-${VERSION}`` instead of under ``${PREFIX}``
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directly, where ${libdir} defaults to ${PREFIX}/lib. Symbolic links
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to these files will be added under ``${PREFIX}/bin``,
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``${PREFIX}/sbin``, and so on.
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As only each version itself has the authoritative knowledge of which |
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files belong to it, each version provides two executables ``install`` |
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and ``uninstall`` that add and remove the symbolic links, |
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respectively. Both executables will be idempotent and only touch |
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symbolic links that are outside the directory for their version of |
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Ganeti and point into this directory. In particular, an ``uninstall`` |
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of one version will not interfere with an ``install`` of a different |
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version. |
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``${libdir}/ganeti/${VERSION}`` instead of under ``${PREFIX}``
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directly, where ``${libdir}`` defaults to ``${PREFIX}/lib``.
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``${libdir}/ganeti/default`` will be a symlink to ``${sysconfdir}/ganeti/lib``
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which, in turn, is a symlink to ``${libdir}/ganeti/${VERSION}``.
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Symbolic links to the files installed under ``${libdir}/ganeti/${VERSION}``
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will be added under ``${PREFIX}/bin``, ``${PREFIX}/sbin``, and so on. These
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symbolic links will go through ``${libdir}/ganeti/default`` so that the
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version can easily be changed by updating the symbolic link in |
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``${sysconfdir}``.
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The set of links for ganeti binaries might change between the versions. |
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However, as the file structure under ``${libdir}/ganeti/${VERSION}`` reflects
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that of ``/``, two links of differnt versions will never conflict. Similarly, |
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the symbolic links for the python executables will never conflict, as they |
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always point to a file with the same basename directly under |
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``${PREFIX}/share/ganeti/default``. Therefore, each version will make sure that
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enough symbolic links are present in ``${PREFIX}/bin``, ``${PREFIX}/sbin`` and
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so on, even though some might be dangling, if a differnt version of ganeti is |
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currently active. |
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The extra indirection through ``${sysconfdir}`` allows installations that choose
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to have ``${sysconfdir}`` and ``${localstatedir}`` outside ``${PREFIX}`` to
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mount ``${PREFIX}`` read-only. The latter is important for systems that choose
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``/usr`` as ``${PREFIX}`` and are following the Filesystem Hierarchy Standard.
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For example, choosing ``/usr`` as ``${PREFIX}`` and ``/etc`` as ``${sysconfdir}``,
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the layout for version 2.10 will look as follows. |
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:: |
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/ |
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+-- etc |
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| | |
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| +-- ganeti |
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| +-- lib -> /usr/lib/ganeti/2.10 |
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| +-- share -> /usr/share/ganeti/2.10 |
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+-- usr |
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+-- bin |
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| +-- harep -> /usr/lib/ganeti/default/usr/bin/harep |
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| ... |
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+-- sbin |
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| +-- gnt-cluster -> /usr/share/ganeti/default/gnt-cluster |
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| ... |
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+-- ... |
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+-- lib |
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| +-- ganeti |
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| +-- default -> /etc/ganeti/lib |
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| +-- 2.10 |
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| +-- usr |
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| +-- bin |
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| | +-- htools |
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| | +-- harep -> htools |
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| | ... |
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| ... |
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+-- share |
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+-- ganeti |
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+-- default -> /etc/ganeti/share |
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+-- 2.10 |
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+ -- gnt-cluster |
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+ -- gnt-node |
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+ -- ... |
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+ -- ganeti |
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+-- backend.py |
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+-- ... |
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+-- cmdlib |
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| ... |
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... |
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gnt-upgrade |
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----------- |
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- If the action is a downgrade to the previous minor version, the |
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configuration is downgraded now, using ``cfgupgrade --downgrade``. |
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- The current version of ganeti is deactivated on all nodes, using the |
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``uninstall`` executable described earlier. |
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- The new version of ganeti is activated on all nodes, using the |
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``install`` executable described earlier. |
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- The ``${sysconfdir}/ganeti/lib`` and ``${sysconfdir}/ganeti/share``
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symbolic links are updated. |
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- If the action is an upgrade to a higher minor version, the configuration |
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is upgraded now, using ``cfgupgrade``. |
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