If you find that your Indexing Server (Keyword Search) stops for any reason you may find that you get a message that looks like this:
The CRM search index service has not been run since 21/12/20XX. Please verify that the index service is configured correctly.
If the message persists after an IIS reset and even after a full system restart then you may need to reinitialise the indexing service.
This can be done in a number of ways
It is possible to kick start the re-index by changing the Field Level Security on a field. Place some Field Level Security (for example deny rights) on any text field of one of the primary entities it will start a full index. You can put it on a field and take it off immediately if you like.
It is also possible to kick off a full re-index by selecting one of the keyword search views (ie. vSearchListCompany) and unchecking the Keyword Search checkbox for the view and Save. Then re-check the Keyword Search checkbox and Save again. This will also start a full re-index.
A very good way to rebuild the index is to delete the FullText.ix folder from the Library then wait for the Incremental index to kick in again and it will start to build up a full index again. The Incremental index occurs every 5 mins by default but this can be changed by going into Administration > System > Keyword Search > Set the Interval.