is there any upgrade path to get my alfresco 2.1.0 ce (with mysql database) to 4.0e ce?
I've looked in the official documentation and it says community directly to 4.0 or enterprise via 2.2.8 and 3.4.7.
The Upgrade how to doesn't address anything 2.1.0 related like the mysql database and the wiki's documentation link points to the alfresco enterprise documentation. I've searched the wiki for other upgrade instructions, but they are the same like in the enterprise documentation. I've also searched for version 2.2.8 and 3.4.7 but cant find a download link to these version.
Currently i've have no idea how to start the upgrade.
I have no idea if this will work in your case, You may have to put in an extra step with upgrade lets say from Labs 3 Final -> 3.2r2 -> 3.4.d. What you do is that you start trying. It is not that hard as you may think, what I would do (in test environment first of course) Make an install of each version, pointing to the same database and document store (alf_data) /opt/alf210 /opt/alflabs3 /opt/alf34d …
Then you start each one in turn, the first one being you current version to verify that it is starting and working ok. You just need to start, let the upgrade do its thing, verify that it works, stop and move to next version. Once you have a working upgrade path, you can do the same for your production environment.
EDIT: I should add that for those upgrade installs, you do not need to worry so much about configuring openoffice, pdf2swf, cifs, ftp or whatever you are using in your alfresco install. Only if you have custom models, they need to be present in your install. What we are looking for is only the upgrade scripts to run. On the final version of course you need to do the full config.
Do i have to care about the old mysql database, should i be migrating to postgres? The only configured setting in the 2.1 installations seems to be user authentication over ldap.
You of course need to configure connection to your mysql db, there is where the upgrade takes place. But for the intermediate upgrades, no need to configure ldap. So intermediate upgrades, only db connection strings, correct path to alf_data (dir.root setting) and any custom models in place (that includes if you have installed any addons and their data models).