View source for FAQ Revert an Update or Installation with p2

Updating your Eclipse plugins may occasionally result in a b0rk3d install.  This situation usually occurs when somebody hasn't properly managed versions and inadvertently introduced an incompatibility that didn't surface during testing.  Fortunately Eclipse manages its updates and installations using a checkpointing mechanism called <em>p2</em>, and p2 allows selectively uninstalling existing features as well as reverting to previous checkpoints.

{{note|
p2's checkpoints, called a <em>profile</em>, record just the set of artifact names and versions that were installed at a particular moment in time.  p2 assumes that it can recreate a previous checkpoint by obtaining the corresponding artifacts.  If p2 cannot resolve artifacts from its local caches or its configured remote repositories, then the process will fail.  This caveat is very important if you install artifacts from repositories whose contents are frequently replaced (e.g., nightly builds).
}}

If you can bring up the UI, then you can [http://eclipsesource.com/blogs/2009/10/02/reverting-changes-in-an-eclipse-installation-using-p2/ revert the change from within the Eclipse About dialogs].  

But sometimes even the UI won't come up.  Fortunately can use the command-line [http://help.eclipse.org/indigo/index.jsp?topic=/org.eclipse.platform.doc.isv/guide/p2_director.html p2 director] to revert:

# You first need to determine your p2 profile name.  Look inside your Eclipse installation in the <code>p2/org.eclipse.equinox.p2.engine/profileRegistry/</code> directory.  There is likely a single directory called <code>PPPPPP.profile</code> (e.g., SDKProfile.profile).  The <code>PPPPPP</code> is the name of your profile.
# Inside this profile directory are a set of files of the form <code>TTTTTT.profile.gz</code> where <code>TTTTTT</code> is a numeric timestamp.  These timestamps are ordered.  The latest timestamp is your current profile, resulting from your last installation or update, and the second-last timestamp is the profile before you did your last installation or update.  Remember this second-last timestamp.
# You need to gather the p2 repositories where artifacts can be resolved from
# You will now invoke the p2 director from the command-line with the profile name <code>PPPPPP</code> and the previous timestamp <code>TTTTTT</code> as determined in the previous steps.
::* on Windows, use the <code>eclipsec.exe</code> instead of ./eclipse
::* on Mac builds since Mars (4.5) M6, use <code>Eclipse.app/Contents/MacOS/eclipse</code> instead of ./eclipse
    ./eclipse -application org.eclipse.equinox.p2.director -profile <em>PPPPPP</em> -revert <em>TTTTT</em> \
        -noSplash -repository <em>comma,separated,repository,urls</em>

If all the referenced artifacts can be resolved, then your installation should be reverted to its previous state.

The [http://help.eclipse.org/index.jsp?topic=/org.eclipse.platform.doc.isv/guide/p2_director.html p2 director] also supports installing and uninstalling artifacts from the command-line.

=== Example ===

Eclipse committers frequently update to the latest integration builds.  Occasionally one of the I-builds goes bad.  To revert, they'd run something like:

    ./eclipse -noSplash -consolelog -application org.eclipse.equinox.p2.director \
        -profile SDKProfile -revert 1429305715350 \
        -repository http://download.eclipse.org/eclipse/updates/4.5-I-builds

=== Revert doesn't work ===

Unfortunately, because of p2 design flaws, revert usually doesn't work when you need it. If one of the update sites that contained any of the artifacts you try to restore doesn't exist any more or doesn't contain that old artifact any more, then revert fails ({{bug|464700}}, {{bug|347150}}). As a workaround, you can try to uninstall and then re-install the artifact.

Example: You have an Eclipse install where you used http://download.eclipse.org/eclipse/updates/4.7-I-builds to update the Eclipse SDK. Later, you updated to Eclipse SDK I20170109-2000, but you find a bug that prevents you from doing work with that build. You want to install Eclipse SDK I20170108-2000 instead, but the broken p2 design wouldn't let you do that, and revert doesn't work because the original build is not available any more.

You need a separate install of the p2 director application which can uninstall I20170109-2000 and then install I20170108-2000. You can't do that using only your install, because uninstalling Eclipse SDK I20170109-2000 also uninstalls the p2 director and the eclipse executable.

Workaround (transcript is for macOS; adapt paths to your setup):

 Paths:
 /Volumes/Eclipse/4.6-M-builds.app/ -- a compatible p2 director install
 /Volumes/Eclipse/4.7.app/ -- Eclipse SDK I20170109-2000 + other plug-ins; the broken install

 $ cd /Volumes/Eclipse/4.6-M-builds.app/Contents/MacOS/
 $ ./eclipse -application org.eclipse.equinox.p2.director -destination /Volumes/Eclipse/4.7.app/ -uninstallIU org.eclipse.sdk.ide
 $ ./eclipse -application org.eclipse.equinox.p2.director -destination /Volumes/Eclipse/4.7.app/ -repository http://download.eclipse.org/eclipse/updates/4.7-I-builds -installIU org.eclipse.sdk.ide/4.7.0.I20170108-2000

The available versions can be found using -list, e.g.:
 $ ./eclipse -application org.eclipse.equinox.p2.director -destination /Volumes/Eclipse/4.7.app/ -repository http://download.eclipse.org/eclipse/updates/4.7-I-builds -list org.eclipse.sdk.ide


[[Category:FAQ]][[Category:Equinox_p2]]