raster - Geoserver ImageMosaic: error connecting to WorldImage

I would like to use the ImageMosaic plugin to set up a Geoserver layer which refers to a WorldImage, just like in the official tutorial.

As a simple test case, I put a custom folder into my Geoserver data directory with one World Image (image + WorldFile + projection). When I specify the folder location to a ImageMosaic Store in Geoserver, it simply displays the error message:

Could not list layers for this store, an error occurred retrieving them: Argument "value" should not be null.

On the other hand, when I put my image into a default folder that comes with the openGeo suite (like file:data/dem/ with the Medform Digital Elevation Data), the thing works as it should.

So I suspect there is something going wrong with user rights, can anybody enlighten me?

---

PS: My Geoserver error log

    INFO [geoserver.web] - Getting list of coverages for saved store file:mosaic
    java.lang.RuntimeException: Could not list layers for this store, an error occurred retrieving them: Argument "value" should not be null.
    at org.geoserver.web.data.layer.NewLayerPageProvider.getItemsInternal(NewLayerPageProvider.java:123)
    ...
    Caused by: java.lang.IllegalArgumentException: Argument "value" should not be null.

    at org.geotools.util.SoftValueHashMap.ensureNotNull(SoftValueHashMap.java:140)
    ...

Answer

The simple solution: contrary to other data sources for Geoserver, it seems that when you deal with an ImageMosaic you strictly need your data folder to be owned by user/usergroup tomcat6. So changing the user/usergroup from root to tomcat6 resolved the problem for me.

Useful commands for Linux:

• display file ownership: $ ls -l (2nd column: owner, 3rd column: owner group)


• change file owner: $ chown myownername myfile (add option -R for folders)


• change file owner group: $ chgrp myownername myfile (add option -R for folders)