postgres=# update pg_database set datallowconn = TRUE where datname = 'template0';
UPDATE 1
postgres=# \c template0
You are now connected to database "template0".
template0=# update pg_database set datistemplate = FALSE where datname = 'template1';
UPDATE 1
template0=# drop database template1;
DROP DATABASE
template0=# create database template1 with template = template0 encoding = 'UTF8' lc_ctype = 'en_US.UTF-8' lc_collate = 'en_US.UTF-8';
CREATE DATABASE
template0=# update pg_database set datistemplate = TRUE where datname = 'template1';
UPDATE 1
template0=# \c template1
You are now connected to database "template1".
template1=# update pg_database set datallowconn = FALSE where datname = 'template0';
UPDATE 1