As James/Bryce correctly point out, the two versions will run on different ports.
However the command line utilities will also be run as one version or the other. For example
pg_dump --version might give you an unexpected result.
You can configure this in a file called
First you need to know the cluster names, to find this, run the following command:
This will output the clusters available eg on my system I'm running 9.6 and 13:
Ver Cluster Port Status Owner Data directory Log file
9.6 main 5432 online postgres /var/lib/postgresql/9.6/main /var/log/postgresql/postgresql-9.6-main.log
13 main 5433 online postgres /var/lib/postgresql/13/main /var/log/postgresql/postgresql-13-main.log
Then create the file
~/.postgresqlrc and put the following to control the default version used:
# Version Clustername Database
13 main postgres
13 to the version you want to run as default, in the case of this question that will be