Hello Thomas,
It is cache part is complete. One collection is handle_info which contains checksum, timestamp and reference from other collection handles which contains unique list of handles.
so in short handles in handles collection are pointing to data in handle_info collection.
Also even after running "$mongod --dbpath ~/opt/mongodb " database path remained to /var/lib/mongodb ( i dont know why). I tried many times but path remains same. What i suggest we can make symlink of /var/lib/mongodb to ~/opt/mongodb.
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Rishabh Sharma
Software Developer
Anantya R&D
http://www.anantyarnd.in