I'm not knew that system catalogs could be saved as schema, thanks Achilleas.
So, I would like to get the data and the schema of the system catalogs. How can I include the data in a dump file with system schemas? (The parameter -a makes sense together the parameter --schema?)
To clarify, you cannot dump the pg_catalog schema. It is the main control of how all other objects are stored in the cluster. There is no point in dumping it and all it's tables and views are already clearly documented. https://www.postgresql.org/docs/9.6/static/catalogs.html