Migrating a Plone site off to another database (Zeo)

Another of the interesting things in my professional life has been migrating a Plone site from one database (where it lived as a dev site, along with many others) onto a nice, clean database of its own.  Now, yes, I’m aware that the export/import feature of Zope isn’t supposed to be used for migrating content or sites.  I am also aware, however, through personal experience, that things have always been fine because I’m using the same eggs and essentially the same installations everywhere, thanks to buildout.

So, the process goes as follows, with the above-mentioned points considered already:

  1. Head to the root of your ZMI and export your given Plone site  as ZEXP
  2. Shut down your instance (or do what you will with your old site and installation)
  3. Copy the ZEXP file into the ‘import’ folder of your new Zope instance
  4. Start your new instance, with your new empty database
  5. Log in to the root of the ZMI
  6. Add a new Plone site and call it anything you want (eg ‘foo’).  I’ll explain why shortly.
  7. Delete your ‘foo’ Plone site.
  8. Import your existing Plone site and be happy because it’s now arrived safe and sound.


The reason I highlight adding a new Plone site a point 6 is because if originally, you were like me and imported your site first to a bare Zope install, you’ll get errors everywhere in your site.  They’ll look like “AttributeError: getGroups” or possibly something more obscure (if possible!) and everything will fall over and die.

Now, by creating a new Plone site first ‘massages’ the root of Zope, and then your site should be fine.  Among other things, adding a site changes the acl_users of the ZMI (seeing an abnormal acl_users is what led me to the solution).  At a guess, given its type, this acl_users change probably has something to do with the error above.

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