Config DB
Generally, never write data to this.
It is maintained by mongo.
It DOES have useful in it.
Check it out
connect to the mongos instance of a sharded cluster && get some shard deets
sh.status()THAT data is in the config db
use config
show collections
# show each db in the cluster as a document
# partitioned means sharding has been enabled
db.databases.find().pretty()
# return deets on collections that have been sharded
# show what field they have been sharded on
db.collections.find().pretty()
# host name of shards
db.shards.find().pretty()
# each chunk per collection is returned as a doc
# inclusive min
# exclusive max
db.chunks.find().pretty()
# mongos processes on the cluster
# the mongo version is included
db.mongos.find().pretty()