[OSM-newbies] No map, only coastlines when browsing slippymap

[pradeep roy]

I am working on creating an OpenStreetMap tile server on CentOS 6.4.
All that I get when loading the slippymap.html page for the "local
tiles" layer is a map with just two colors white and blue for the land
and water. That is, I see an image basically of the coastlines. The
"mapnik" layer works fine.

This is the first time I am doing software configuration related to
maps. All terms like mapnik, osm2pgsql, postgis, tile and so on are
new to me.

As far as I have seen from google search results, there does not seem
to be readily available information on creating this server on CentOS
6.x. So, for me, the main set of instructions has been the following
document:

http://switch2osm.org/serving-tiles/manually-building-a-tile-server-12-04/ [1]

All the components either had to be installed from third-party CentOS
repositories like ELGIS, RPMForge, EPEL and PGDG92 or compiled from
source.

A few days back, I did create the same server on Ubuntu 12.04, which
was straightforward. These instructions were followed:

http://switch2osm.org/serving-tiles/building-a-tile-server-from-packages/ [2]

Note that document [2] mentions about accessing the slippymap.html but
[1] does not. In [1], the only test mentioned is accessing
http://yourserveraddress/osm_tiles/0/0/0.png which works fine even in
my CentOS 6.4 setup. I created the slippymap.html by copying from the
Ubuntu 12.04 box and minor editing.

How do I debug this issue? What could be the problem? Are there any
checklists to verify the proper functioning of each of the components
like osm2pgsql, the postgres/postgis db, mod_tile or mapnik?

Thanks,
Pradeep