Postgresql pg_upgrade failed : role unknown

Problem :

When migrating a database, pg_upgrade failed with “could not connect, role <XXX> is unknown”.

My database was created with another user (postgresql)

Then transfered to another user (let's call it john)

The login authentication was password only until upgrade, where I put local to trust for upgrade.

The new destination database was created by john.

Solution :

The pg_upgrade can not use : 

• an old database with super role postgres
• a new database with super role john

The option “-U <username>” is applied to the both, so there is always one which is wrong.

So rename the old database super role to john (thanks to internet).

1. start the old database, pg_upgrade give the command in the log but !!

• Be careful ! there is a hidden option “-b” which prevent any modification :) remove it and all is ok

"/home/myuser/postgresql-9.6.2/bin/pg_ctl" -w -D "/home/myuser/database-introscope-9.6" -o "-p 50432  -c listen_addresses='' -c unix_socket_permissions=0700 -c unix_socket_directories='/home/myuser'" start

Connect with : 

/home/myuser/postgresql-9.6.2/bin/psql -p 50432 -h /home/myuser -U postgres -d postgres

Check the super user role name : 

SELECT rolname FROM pg_roles WHERE oid = 10;

Create another super user

CREATE ROLE spiderman SUPERUSER LOGIN PASSWORD 'moreSecurePass';

Quit, connect with spideman, still on postgres database

/home/myuser/postgresql-9.6.2/bin/psql -p 50432 -h /home/myuser -U spideman -d postgres

Rename the original role :

alter role postgres rename to john;

Check the connection :

/home/myuser/postgresql-9.6.2/bin/psql -p 50432 -h /home/myuser -U john -d postgres

Drop spiderman role : 

DROP ROLE spiderman;

I learn to side tricks here : 

• -h<path> : give the path to the unix socket connection
• -b option : use for binary upgrade mode on pg_ctl (didn't see the option in the documentation)
• Owner role has value OID=10