How To Use Registry Rebuild With Drush in multisite
There are times in Drupal 7 when the registry gets hopelessly hosed and you need to rebuild the registry (a list of PHP classes and the files they go with). Sometimes, though, you can't do this regular cache-clear activity because some class is required when the system is trying to bootstrap. (such as moving modules folder to another folders / multisite things)
This is the preferred technique, and it should work with multisite installs.
1.You can just drush dl registry_rebuild and drush will download it into your .drush folder. (Alternately, you can obtain the package another way and copy the folder into .drush yourself.)
2.Make a backup of your database.
3.On a multisite install, cd into the site you're rebuilding, as in cd sites/mymultisite
Need more help or details? comment out !