Re: pg_upgrade -c cannot be run if old cluster is running

[Tom Lane]

Alain Bourgeois <alain.bourge...@zetes.com> writes:
> /usr/lib/systemd/system/postgresql-10.service has 
> PGDATA=/var/lib/pgsql/10/data/, /var/lib/pgsql/10/data/postgtresql.conf holds 
> data_directory = '/mnt/pgdata/pgdir'

This is probably the source of your problem.  IIRC, pg_upgrade
needs to be pointed at the actual old data directory, not
PGDATA=/var/lib/pgsql/10/data.

                        regards, tom lane