Migrate Zope/Plone from CentOS to Ubuntu

I don’t use Zope and Plone anymore, but if you’ve played with Zope/Plone you know they are highly proprietary, fragile, missing a lot of desirable functionality, and overall pretty painful to manage. About the only thing I really ever liked about them was the relative ease of integrating Python libraries and code. Regardless, I sometimes had to move Zope installs around between servers, so this is one of the procedures I used.

In this case, I needed to migrate an old Zope 2.9/Plone 2.5.5 instance and its back-end PostgreSQL 8.1 database hosted on two separate CentOS 6 servers to a single Ubuntu 12.04 system. The Zope/Plone instance was created with the Plone universal installer, so it had its own version of Python (2.4.4) with which its plug-in products were compiled. The PostgreSQL database was on the second server, and the Zope/Plone instance spoke to Postgres using the ZPsycopgDA2 Zope/PostgreSQL database connector, a Zope product built on the Python psycopg2 library.

The process went as follows:

On the Ubuntu system, installed postgresql 8.4, changed password for database superuser (postgres), and adjusted configuration files in /etc/postgresql to make it listen on correct ports. Then I dumped the database from the PostgreSQL 8.1 instance, imported the SQL dump into the new PostgreSQL 8.4 instance, and connected with pgAdmin to ensure all the data was there.
Stopped the zeo and posgresql services on the two CentOS systems.
Copied the original Zope instance to /opt/Plone-2.5.5 on the Ubuntu box, added a plone user, adjusted permissions on Plone directory to match the original, and ensured the cache and port settings in the zope.conf configuration file were correct.

On the Ubuntu server, started the zeocluster to ensure it works — it did, mostly, with a couple of broken products:

File "/opt/Plone-2.5.5/Python-2.4.4/lib/python2.4/site-packages/psycopg2/__init__.py", line 55, in ?
    from psycopg2 import tz
ImportError: cannot import name tz

Installed the libpq-dev Python/PostgreSQL library, then ran the Zope version of the Python interpreter and tried to import psycopg2, with the following error:
```
ImportError: libpq.so.4: cannot open shared object file: No such file or directory
```
Created a symbolic link from the new libpq library to the old one:
```
ln -s /usr/lib/libpq.so.5 /usr/lib/libpq.so.4
```

Restarted the zeocluster again, then discovered that the CAS authentication we use for logins was also broken, with the errors:

2013-01-18T17:09:47 ERROR Zope.SiteErrorLog http://redacted/index_html
Traceback (innermost last):
  Module ZPublisher.Publish, line 106, in publish
  Module ZPublisher.BaseRequest, line 452, in traverse
  Module Products.PluggableAuthService.PluggableAuthService, line 234, in validate
  Module Products.PluggableAuthService.PluggableAuthService, line 560, in _extractUserIds
  Module Products.CAS4PAS.CASAuthHelper, line 147, in extractCredentials
  Module Products.CAS4PAS.CASAuthHelper, line 164, in validateTicket
  Module urllib, line 187, in open
  Module urllib, line 199, in open_unknown
IOError: [Errno url error] unknown url type: 'https'

The Python 2.4.4 shell in the Zope instance showed the following:

>>> import httplib
>>> hasattr(httplib, 'HTTPS')
False
>>> import socket
>>> hasattr(socket, 'ssl')
False
>>> import _ssl
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
ImportError: libssl.so.6: cannot open shared object file: No such file or directory

Set two more symbolic links to fix the authentication problems:

ln -s /usr/lib/x86_64-linux-gnu/libcrypto.so libcrypto.so.6
ln -s /usr/lib/x86_64-linux-gnu/libssl.so libssl.so.6

CAS authentication then worked properly.

On the Ubuntu system, installed apache2 to act as proxy for the Zope instance. Added a few Apache modules:
```
$ a2enmod rewrite
$ a2enmod proxy
$ a2enmod proxy_balancer
$ a2enmod proxy_http
```

Created a virtual host configuration file in /etc/apache2/sites-available/mysite.com:

<VirtualHost *:80>
  ServerAdmin webmaster@localhost
  ServerName mysite.com

  ProxyVia On

  # prevent global HTTP proxy
  <LocationMatch "^[^/]">
      Deny from all
  </LocationMatch>

  <Proxy *>
      Order deny,allow
      Allow from all
  </Proxy>

  RewriteEngine on
  RewriteRule ^/(.*) http://localhost:8080/VirtualHostBase/http/mysite.com:80/mysite/VirtualHostRoot/$1 [P,L]
</VirtualHost>

Then enabled the site and restarted Apache:

$ a2ensite mysite.com
$ service apache2 restart

Finally, added a link to the zeo startup script in /etc/rc.local so Zope will run when the Ubuntu box starts up.

(Compare this to Drupal, which runs on a very standard technology stack and offers the ability to clone web sites and databases from one box to another with Drush.)

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