Short walkthru
Migrating_PostgreSQLold=9.3
new=9.4
/etc/init.d/postgresql-$old stop
rc-update del postgresql-$old
eselect postgresql set $new
su - postgres
ln -s /etc/postgresql-$old/*.conf /var/lib/postgresql/$old/data
ln -s /etc/postgresql-$new/*.conf /var/lib/postgresql/$new/data
initdb /var/lib/postgresql/9.4/data \
-E utf8 --locale=en_US.UTF-8 --lc-collate=C
pg_upgrade94 \
-b /usr/lib64/postgresql-$old/bin \
-B /usr/lib64/postgresql-$new/bin \
-d /var/lib/postgresql/$old/data \
-D /var/lib/postgresql/$new/data
exit
mv /var/lib/postgresql/$new/data/*.conf /etc/postgresql-$new
/etc/init.d/postgresql-$new start
rc-update add postgresql-$newdefault