Thanks, now 3 versions, 14, 15, and 16 are running as shown below. I did pg_upgrade as detailed below, but it asked me to shutdown postmaster, should which postmaster be down and how?
##three
#sudo pg_lsclusters
Ver Cluster Port Status Owner Data directory Log file
14 main 5432 online postgres /var/lib/postgresql/14/main /var/log/postgresql/postgresql-14-main.log
15 main 5434 online postgres /var/lib/postgresql/15/main /var/log/postgresql/postgresql-15-main.log
16 main 5433 online postgres /var/lib/postgresql/16/main /var/log/postgresql/postgresql-16-main.log
##pg_upgrade
/usr/lib/postgresql/16/bin/pg_upgrade -b /usr/lib/postgresql/15/bin -B /usr/lib/postgresql/16/bin -d /var/lib/postgresql/15/main -D /var/lib/postgresql/16/main --check
There seems to be a postmaster servicing the new cluster.
Please shutdown that postmaster and try again.
Failure, exiting
I tried to install the 15 and 16, but the configuration complained ports and other things.
All of which are issues that simple Postgresql configuration changes can solve.